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1. Hematology-High Yield Topics
For Internal Medicine Boards and Hematology Boards
Target Audience: Internal Medicine Residents, Family Medicine Residents, Hematology Fellows,
Medical Students, IM Board Recertification exam aspirants
Archer Internal Medicine Board Review
www.CcsWorkshop.com
2. History of the platelet
Studies by Osler, Hayam, and Bizzozero identified
small particles in the blood, these were believed to
be either bacteria or red cell fragments
James Homer Wright “Wright Stain” identified
platelets as a distinct hematopoetic component
arising from megakaryocytes
William Duke in 1910 described 3 patients with low
platelet counts that had hemorrhagic disease
Duke created a venous shunt from a normal donor
to a thrombocytopenic recipient and showed that
the platelet count could rise and the bleeding
would cease
4. Thrombopoietin (TPO)
TPO is the primary regulatory protein in the production of platelets.
Has a major effect on almost all steps of megakaryocyte differentiation and
maturation.
Promotes growth of Meg-CFC
Increases the rate of endomitosis
Stimulates megakaryocyte maturation
TPO gene is on chromosome 3.
TPO is expressed in the liver, kidneys, and smooth muscle cells. Produced at a
constant rate by the liver.
Has a plasma half life of 30 hours.
In circulation, most of it removed by thrombopoietin (c-mpl) receptors on
platelets and possibly some by bone marrow megakaryocytes. The residual
thrombopoietin (50 to 150 pg/mL) provides basal stimulation of megakaryocytes
and a basal rate of platelet production.
Hence, when platelet mass falls there is more TPO in the blood ( less clearance)
stimulating megakaryocytes. When platelet mass increases, TPO falls due to
increased clearance and hence, decreased megakaryopoiesis.
5. Thrombocytopenia
Defined as a subnormal amount of platelets in the circulating blood.
Normal platelet count : 150,000 to 450,000/microL. Thrombocytopenia is
defined as a platelet count less than 150,000/microL (150 x 10(9)/L).
Not usually clinically detected until the platelet count falls to levels below
100,000/microL . However, a recent fall in the platelet count by 50%, while still
in the normal range, may herald severe clinical problems requires active
follow-up. eg: HIT .
1/3 of platelets are sequestered in the spleen.
Half life of a platelet is 9 to 10 days.
Platelet production is the function of the multinucleated megakaryocyte.
15 to 45 K platelets are produced daily to maintain steady state
Pathophysiology is less well defined
6. Practical Importance of Thrombocytopenia
1/3 of all Hematology Consults in a General Hospital
are for thrombocytopenia.
5 to 10% of all hospital patients are thrombocytopenic
in the ICU the number increases to 35%.
Thrombocytopenic patients in the hospital suffer a
twofold greater mortality rate than those who are not
7. Clinical Features - Thrombocytopenia
Most conditions are associated with bleeding ( ITP, Drug
induced TP, Most other TPs)
Some conditions associated with thromboses
Thrombotic Thrombocytopenia Purpura (TTP)
Disseminated Intravascular Coagulation (DIC)
Heparin Induced Thrombocytopenia ( HIT)
Sites of bleeding in thrombocytopenia :
Skin and mucous membranes : Petechiae, Ecchymosis, Hemorrhagic
vesicles, Gingival bleeding and epistaxis.
Menorrhagia
Gastrointestinal bleeding
Intracranial bleeding
Bleeding in to joints and soft tissues are manifestation of
coagulation factor deficiencies rather than thrombocytopenia.
8. Stratifying levels of thrombocytopenia
The primary reason for evaluating
thrombocytopenia is to assess the risk of bleeding
and assess the presence of underlying disorders
(TTP, HIT etc.)
< 20 K increased risk of bleeding
20K to 50 K rarely have increased risk of spontaneous
bleeding but increased risk of bleeding from procedures
50K to 100K no increased risk of spontaneous bleeding
and can undergo most procedures
9. Relation of bleeding risk and platelet count
Bleeding time increases in a linear fashion below a
platelet count of 100 K.
In leukemic children major forms of hemorrhage
occurred at platelet counts <10 K.
Slichter et al tagged RBC and found fecal blood loss
10 K - 5 cc/day
5 to 10 K - 10 cc/day
< 5 K - 50 cc/day
10. Approach to the
thrombocytopenic patient
History
Is the patient bleeding?
Do the sites of bleeding suggest a platelet defect?
Duration - Is thrombocytopenia – acute or chronic?
Is there a history of medications, alcohol use, or recent transfusion ( post-
transfusion purpura)?
Are there symptoms of a secondary illness? (neoplasm, infection,
autoimmune disease)
Is there a family history of thrombocytopenia?
Heparin exposure – recent or with in past three months (HIT)?
Are there risk factors for HIV infection?
History of liver disease?
Assess the number of platelets
CBC with peripheral smear :-
Any clumps? Schistocytes? Nucleated RBCs? Any features of nutrional
deficiencies (hypersegmented neutrophils), MDS (hyposegmented neutrophils),
Myelofibrosis ( tear drop cells) ?
Isolated thrombocytopenia or any other cell line affected?
Lab Tests : PT and PTT, autoimmune work-up if suspected, HIV if risk
factors, LFTs, Nutrient work up ( B12, Folate)
11. Thrombocytopenia
Several Causes.
Can be broadly classified in to five categories based on
the mechanism behind reduced platelet count:
Pseudo or Spurious Thrombocytopenia
Dilutional Thrombocytopenia
Decreased Platelet Production
Increased Platelet Destruction
Altered Distribution of Platelets ( Increased Sequestration)
Most common mechanisms are decreased platelet
production and increased destruction.
12. Pseudo Thrombocytopenia
Pseudo Thrombocytopenia : An artifactual clumping of
plateletsin vitro without clinical significance
The first step in evaluating any thrombocytopenia is to
confirm if it is “true”.
Evaluate Peripheral smear for platelet clumps which can
lead to pseudo-thrombocytopenia.
Failure to recognize this phenomenon may lead to
misdiagnosis and subsequent mismanagement of patients
Various Scenarios :
Inadequate anticoagulation of the blood sample : Results in
thrombin induced platelet clumps, counted as leucocytes by
automated cell counters. Hence, spurious thrombocytopenia.
Rarely, WBC count is increased by more than 10%.
EDTA dependant platelet auto-antibodies : “Naturally”
occuring platelet antibodies lead to platelet clumps in the
presence of EDTA ( in-vitro) .
Abciximab Related Pseudo-Thrombocytopenia.
13. EDTA Dependant Aggluttinins
Present in 0.1% of normal population.
Unlike true thrombocytopenias, EDTA-PTCP is
associated with a normal mean platelet volume
These patients have naturally occurring platelet
antibodies directed towards a normally “hidden”
epitope on platelet membrane GP IIb/IIIa complex
The glycoprotein IIb/IIIa complex must dissociate to
exposethis epitope (called the "cryptantigen" or
"neoantigen,“) for antibody binding to occur.
EDTA, Drugs such as Abciximab and Mexiletene , ph
and temperature can induce dissociation of GP IIb/IIIa
and may expose this cryptantigen causing the antibody
to bind and resulting in aggluttination ( clumps).
14. EDTA Dependant Aggluttinins
EDTA – PTCP is diagnosed by examination of peripheral
smear for platelet clumping.
If platelet clumping seen, repeat the count in non-EDTA
anticoagulant ( heparin or sodium citrate).
If citrate is used, remember to correct the platelet count for
dilution caused by amount of citrate solution used. No such
correction required for heparin.
Although pseudothrombocytopenia has no pathologic
significanceand will not increase thrombotic or
hemorrhagic risk, failureto recognize it may potentially
place a patient in jeopardyfor inappropriate
discontinuation of the needed drug (eg: abciximab), delay
of therapies involving invasive procedures, or initiation of
unnecessary therapies, such as platelet transfusion or use of
steroids.1
15. Pseudo-Thrombocytopenia
Platelet clumps seen in EDTA anti-coagulated
blood sample in a patient with EDTA
Dependant platelet aggluttinins
No platelet clumps seen and platelet count
normal in the blood sample from the same
patient anti-coagulated with Sodium Citrate
16. Abciximab - Pseudothrombocytopenia
Thrombocytopenia is a well-recognized adverse effect of abciximab therapy.
Two mechanisms :
Immune mediated thrombocytopenia ( onset with in minutes to hours of
administration rather than days to weeks seen with other drug induced
thrombocytopenias).
Pseudothrombocytopenia, of no clinical importance. ( 1/3rd of
thrombocytopenia” found in patients receiving abciximab is due to
pseudothrombocytopenia)
Abciximab-PTCP is due to the presence of EDTAas an anticoagulant in the
blood-drawing tube. EDTA exposes the cryptantigen in GPIIb/IIIa complex to
aggluttination with naturally occuring antibodies. The mechanism of
abciximab-associated, EDTA-induced plateletclumping is not clear.
Differentiation of Abciximab-PTCP from True Abciximab-TP and from HIT is
extremely crucial. Diagnosis of PTCP will avoid discontinuation of the
abciximab infusion and initiation of unnecessary therapies, such as platelet
transfusions or anticoagulants (as in HIT).
When thrombocytopeniaoccurs after abciximab treatment, first review peripheral
blood film for clumping or obtain platelet count in citrated blood.
17. Abciximab – PTCP
Time course of automated platelet counts from citrated blood and EDTA blood.
18. Dilutional Thrombocytopenia
Large quantities of PRBC transfusion to treat massive
hemmorhage can lead to dilutional TP.
Due to absence of viable platelets in packed RBCs.
Usual platelet counts in patients receiving 15 to 20
units of PRBCs in 24 hours is 50k to 100k/µl.
Can be prevented by giving platelet concentrates to
patients receiving more than 20 units PRBCs in a 24
hour period.
19. Distributional Thrombocytopenia
Also, referred to as Appartent Thrombocytopenia since
total platelet mass is normal.
About 1/3rd of circulating platelets are normally
sequestrated in spleen.
Splenic sequestration of platelets may increase to 90%
in splenomegaly ( hypersplenism) secondary to portal
hypertension or other causes . May be associated with
leucopenia and/ or anemia.
Circulating platelet count decreases but total platelet
mass and overall platelet survival remain normal.
Hence, these patients can have significant “apparent”
thrombocytopenia but rarely have clinical bleeding (
since total available platelet mass is normal)
20. Decreased Platelet Production
Associated with decreased or ineffective
megakaryopoiesis and thrombopoiesis
Marrow Damage:
Aplastic Anemia
Fanconi’s anemia ( defect in DNA repair genes)
Malignancy ( with/ with out Myelophthisis ).
Congenital defects ( Congenital thrombocytopenias)
Paroxysmal Nocturnal Hemoglobinuria
Viral infections: rubella, CMV, EBV,HIV, Hep-C
Ineffective production :
Nutritional Deficiencies: B12, Folate, Severe Fe deficiency
Drugs: thiazides, estrogen, chemotherapy , linezolid
Toxins: alcohol, cocaine
21. Increased Destruction
Most common cause of thrombocytopenia.
Leads to stimulation of thrombopoiesis and thus
an increase in the number, size and rate of
maturation of the precursor megakaryocytes.
Increased consumption with intravascular thrombi
or damaged endothelial surfaces
24. Disseminated Intravascular Coagulation (DIC)
Mechanism
Systemic activation
of coagulation
Intravascular
deposition of fibrin
Depletion of platelets
and coagulation factors
BleedingThrombosis of small
and midsize vessels
with organ failure
26. DIC
Treatment approaches
Treatment of underlying disorder
Anticoagulation with heparin – when thromboses
are an issue
Platelet transfusion – if, bleeding
Fresh frozen plasma – if, bleeding
27. TTP Thrombotic Thrombocytopenia Purpura
Characterized my microangiopathic hemolytic anemia
and profound intravascular platelet clumping.
The disease was first reported in 1923 by Dr. Eli
Moschowitz at Beth Israel in NYC
16 year old girl who presented with anemia, petechia
ultimate coma and death
Terminal arterioles and capillaries were occluded by
hyaline thrombi mostly composed of platelets
28. Lazarchick, J. ASH Image Bank 2001;2001:100174
Figure 1. Peripheral smear showing microangiopathic hemolytic features with numerous RBC
fragments (helmet cells/schistocytes)
30. Clinical and Lab Manifestations of TTP
Severe thrombocytopenia and hemolytic anemia
with one or several fragmented red cells in high
power oil >1% total number of RBC
Neurologic Manifestations, abdominal pain
Fever and Renal Abnormalities occur in the
minority of patients
Thrombocytopenia range from <30 K to 75 to 100 K
Elevated LDH
Initially coagulation studies are normal
31. Type of TTP
Familial chronic relapsing
Acquired idiopathic
HIV related TTP
Pregnancy can trigger both acquired and congenital TTP
Drug related
Ticlopidine, Clopidogrel
Cancers: Adenocarcinoma of breast, GI tract and Proastate
Thrombotic Angiopathies that resemble TTP
Mitomycin, cyclosporine, tacrolimus, quinine
Chemotherapy, gemcitabine, TBI
BM and Solid organ transplant
32.
33. Moake J. N Engl J Med 2002;347:589-600
Proposed Relation among the Absence of ADAMTS 13 Activity in Vivo, Excessive Adhesion and
Aggregation of Platelets, and Thrombotic Thrombocytopenic Purpura
34. Differential Diagnosis of TTP
Other conditions causing MAHA :
Hemolytic-uremic syndrome
DIC
Malignant Hypertension
Pregnancy
Preeclampsia/eclampsia
HELLP
Severe Vasculitis
Evans Syndrome ( Direct Coomb+, No Schistocytes).
Macroangiopathic Hemolysis : Malfunctioning prosthetic
cardiac valves
35. Treatment of TTP
Urgent plasmapheresis ( plasma exchange)
Plasma Infusion : Infusion of FFP 30 cc/kg/day until ready for
plasma exchange ( serves as emergency initial measure in those who
do not have immediate access to Plasma exchange)
Daily plasma exchange with either FFP or cryopoor FFP (45 to 55
cc/kg/day)
Steroids (Prednisone 1 mg/kg/day) ( may help by suppressing
anti-ADAMTS13 antibodies).
Red Blood Cell transfusions if needed
Platelet transfusion may worsen the disease and are avoided.
Used only if absolutely necessary ( in very rare cases, where
severe bleeding is encountered)
Refractory TTP : In patients with worsening disease despite daily
plasma exchange + Steroids Increase plasmpheresis to twice
daily exchange.
Poorly responsive or Recurrent TTP Add Immunosuppressive
therapy -Add Rituximab or Cyclosporine
37. Etiology - Chronic HCV-TP
Pathophysiology of HCV-TP is complex and involves the
interaction of multiple factors
Hepatic Fibrosis and Cirrhosis
Patients with advanced fibrosis had significantly lower mean platelet
counts compared with those having stage 0-2 fibrosis.
Portal Hypertension and Splenomegaly
Splenomegaly and platelet sequestration, or hypersplenism, is seen in 11%
to 55% of patients with cirrhosis and portal hypertension. Hence, these
are not the only factors to explain TP in chronic liver disease.
Bone Marrow Suppression by HCV
Immune Dysfunction
HCV can bind and alter the confirmation of glycoproteins inducing the
formation autoantibodies and there by, immune mediated platelet
clearance. High titers of platelet-associated immunoglobulin G (PAIgG)
(immune complex–coated platelets) found in 88% of patients with
chronic HCV.
Decreased Thrombopoetin levels or activity.
Treatment related Thrombocytopenia. Peg-Interferon ( Inteferon-
TP is due to BM suppression and decreased secretion of TPO)
38. Prevalence of HCV in Chronic ITP
Without Overt Liver Disease
1. Pivetti S, et al. Br J Haematol. 1996;95:204-211. 2. Pawlotsky JM, et al. J Hepatol. 1995;23:635-639.
3. Sakuraya M, et al. Eur J. Haematol. 2002;68:49-53. 4. García-Suárez J, et al. Br J Haematol.
2000;110:98-103. 5. Rajan SK, et al. Br J Haematol. 2005;129:818-824.
Study N Platelet Threshold,
x 109/L
HCV Positive, n
(%)
Pivetti et al[1] 33 < 100 12 (36)
Pawlotsky et al[2] 139 < 25 14 (10)
Sakuraya et al[3] 79 < 10 11 (14)
García-Suárez et al[4] 51 < 100 13 (23)
Rajan et al[5] 250 < 100 76 (30)
39. HCV-TP – Impact on HCV Treatment
Greatest challenge of HCV-TP is difficulty in starting or
maintaining HCV therapy.
Treatment with Peg-inteferon may reduce platelet counts by 33%
Peg-Inteferon :
Initiation of therapy : Can not be initiated if platelet count < 50k/µl
. For standard dose of PEG-Interferon 0.5mcg/kg platelet count
must be greater than 70k/µl . Patients with platelet count 50 –
70k/µl can start at 0.25mcg/kg .
Dose must be reduced if platelet count falls below 50k/µl
Permanently discontinued if platelets fall below 25k/µl.
Postponement of treatment due to thrombocytopenia can result
in diminished sustained virologic response because of the
potential for further progression of liver disease in the absence of
treatment. Dose modifications may lower the chances of
sustained virological response.
40. HCV-TP - Management
Platelet transfusions as indicated per routine trigger levels (
Prophylactic transfusion if less than 10k, prior to procedures or if
bleeding and if less than 50k). Platelet transfusions are not
indicated prior to starting HCV therapy or during therapy unless
patients have active bleeding with platelet count <50k.
Splenectomy and splenic artery embolization :
have been used to correct TP in patients with hypersplenism,
producing significant and persistent increases in platelet counts.
Used prophylactically prior to anti-HCV therapy, this can improve
thrombocytopenia in patients with HCV-induced cirrhosis and
hypersplenism, thus facilitating the use of antiviral therapy.
Risks: peri-op mortality, infections and DIC
41. HCV-TP - Management
Role of TPO receptor agonists: A double blind, phase II trial evaluated whether
eltrombopag could facilitate initiation and maintenance of antiviral therapy.
Median platelet counts at baseline and week4 in HCV patients treated with
Eltrombopag.
Peg-interferon + ribavirin therapy initiated if platelet counts increased to
greater than 70k. number of patients able to initiate antiviral treatment was
80% with eltrombopag vs 22% in the control arm. In total, 65% of patients in
the 75-mg dose group, 53% of patients in the 50-mg dosing group, and 36% of
patients in the 30-mg dosing group were able to complete the 12-week antiviral
therapy phase compared with 6% of placebo-treated patients
Not FDA approved yet. Pivotal phase III studies are underway to further
examine eltrombopag in chronic hepatitis C patients with thrombocytopenia.
42. Drug Induced Thrombocytopenias
Classified as :
Direct Toxicity
BM Suppression
Immune mediated destruction
Pro-hemorrhagic : all other drugs
Pro-Thrombotic : Heparin
46. Frequency of HIT
Perspectives
More than 1 trillion units heparin used yearly in
US; 1/3 of hospitalized exposed (12 million).
Unfractionated heparin – 3 - 5% incidence;
Heart surgery 2.5% incidence
LMWHeparin, Catheter-flushes -- ~0.5%
Frequency of thromboemboli : 30%–50% of
patients with untreated HIT will have a thrombotic
complication within 30 days ( Warkentin TE Am J Med.
1996;101:502–507) Based on increased morbidity and
mortality, heparin cessation alone is inadequate in HIT
management
48. HIT
Two types – HIT type I and Type II. In general, the
term HIT is used widely to refer HIT Type II, the
immune form.
Presence of any of the following :
Otherwise unexplained thrombocytopenia
Venos or arterial thromboses associated with
thrombocytopenia
A fall in platelet count of 50% or more from a prior
value, even if absolute Thrombocytopenia is not
present.
Necrotic skin lesions at heparin injection site
Acute systemic ( anaphylactoid) reactions occuring after
IV heparin bolus.
49. Diagnosis of HIT
Normal platelet count before commencement of
heparin therapy
Onset of thrombocytopenia typically 5–14 days after
initiation of heparin therapy but can occur earlier
Exclusion of other causes of thrombocytopenia (eg,
sepsis)
Occurrence of thromboembolic complications during
heparin therapy
51. • 30%–50% of untreated patients with
thrombocytopenia progress to thrombosis
4:1 Incidence Ratio Venous to Arterial
Arterial
Aortic/Ileofemoral Thrombosis
Acute Thrombotic Stroke
Myocardial Infarction, Mural
thrombosis, Thrombi in upper limb,
mesenteric, renal and spinal arts.
Venous
Deep Vein Thrombosis
Pulmonary Embolism
Cerebral Dural
Sinus Thrombosis
Adrenal Hemorrhagic Infarction
Sites of Thrombotic Complications
in HIT
Warkentin TE Am J Med 1996;101:502–507
52. HIT Temporal Variants
Day 1 Day 4 Day 14
Day 30
Delayed-onset
HIT
(9–40 days)
Rapid-onset
HIT
(hours–days)
Typical HIT
Mean Day 9
(5–14 days)
Heparin (re) Exposure
THROMBOCYTOPENIA (± THROMBOSIS)
53. Clinical Suspicion for HIT
The 4 T’s (Warkentin, 2003)
Thrombocytopenia
Platelet count fall > 50% and nadir greater than 20k : 2 points
Platelet count fall 30 to 50% or nadir 10 to 19k : 1 point
Platelet count fall < 30% or nadir < 10k : 0 points
Timing of platelet count fall
Clear onset b/w days 5 to 10 or platelet count fall at ≤1 day if prior
heparin exposure within the last 30 days: 2 points
Consistent with fall at 5 to 10 days but not clear (eg, missing platelet counts)
or onset after day 10 or fall ≤1 day with prior heparin exposure within the last
30 to 100 days: 1 point
Platelet count fall at <4 days without recent exposure: 0 points
Thrombosis or other sequelae
Confirmed new thrombosis, skin necrosis, or acute systemic reaction after
intravenous unfractionated heparin bolus: 2 points
Progressive or recurrent thrombosis, non-necrotizing (erythematous) skin
lesions, or suspected thrombosis which has not been proven: 1 point
None: zero points
Other causes for thrombocytopenia present —
None apparent: 2 points
Possible: 1 point , Definite: zero points The 5th T : The TEST
54. Interpretation
A score is determined for each of the four above
categories, resulting in a total score from zero to 8.
Pretest probabilities for HIT are, as follows:
zero to 3: Low probability
4 to 5: Intermediate probability
6 to 8: High probability
Laboratory tests are ordered to confirm HIT.
55. Laboratory Testing for HIT
Test Advantages Disadvantages
SRA Sensitivity >95%,Technically demanding
Specific > 95% Low predictive value
HIPA Rapid, available Variable sensitivity (30% – 80%);
Technique-dependent
ELISA High sensitivity High cost, less specificity,
> 95% 10% false-negative tests
There is no Gold Standard in diagnostic testing; HIT
requires a clinical diagnosis .
56. HIT - Managment
Stop all Heparin, including heparin flushes. If dialysis,
must be Heparin free.
Platelet transfusions are relatively contraindicated. ( except
in those with overt bleeding).
If Intermediate or High pre-test (clinical) probability +
Positive ELISA (Anti-PF4 antibody) Start alternative
anticoagulant.
For low clinical probability, positive ELISA consider false
positive ELISA. Obtain Serotonin Release Assay which is
more specific.
If clinical probability increases over time from a prior
value but if initial HIT was negative Repeat HIT
antibody (ELISA) (may turn positive. ) Start alternative
anticoagulant
57. Alternative Anticoagulants
Drug Indications
Argatroban FDA-approved for HIT
(also for PCI)
Lepirudin FDA-approved for HIT
Bivalirudin (Angiomax) PCI (including HIT patients)
Fondaparinux (Arixtra) FDA approved for DVT
Prophylaxis in patients with Hip#,
Hip or knee replacements. Also
used in Rx of VTE. Not yet
approved for HIT (Off-label use)
Danaparoid Approved for HIT in Canada,
Europe, Aust.
58. Argatroban
Synthetic Direct Thrombin Inhibitor indicated as a
prophylactic anticoagulant or for treatment of thromboses in
HIT.
MOA : Directly inhibits Thrombin, Reversibly binds to the
thrombin catalytic site and Active against both free and clot-
bound thrombin
Rapid Onset of Action
In healthy subjects, the pharmacokinetics and
pharmacodynamics of Argatroban were NOT affected by renal
impairment, age, or gender Dosage adjustment is NOT
necessary in renally impaired patients
Hepatic impairment decreases Argatroban clearance;
therefore, the dosage must be reduced for hepatically
impaired patients
59. Guidelines
for Argatroban
HIT
Patients
HIT Patients with
Renal
Impairment
HIT Patients with
Hepatic
Impairment
* Not to exceed a dose of 10 µg/kg/min or aPTT of 100 seconds
† Due to approximate 4-fold decrease in Argatroban clearance relative to those with normal
hepatic function
Initiate at
2 µg/kg/min
Titrate until
steady-state
aPTT is 1.5–3.0
times baseline
value*
No dosage
adjustment
required
Initiate at
0.5 µg/kg/min†
Titrate until
steady-state
aPTT is 1.5–3.0
times baseline
value*
60. Guidelines for Conversion to Oral Anticoagulant Therapy
Initiate warfarin only when platelet count increases above 100k.
All direct thrombin inhibitors, including Argatroban, may increase
prothrombin time (PT); this must be taken into consideration when
converting to warfarin therapy
Coadministration of Argatroban and warfarin does produce a combined
effect on the laboratory measurement of the INR.
Concurrent therapy with Argatroban and warfarin does not exert an
additive effect on the warfarin mechanism of action (e.g., factor Xa
activity)
The previously established relationship between INR and bleeding risk is
altered during combination therapy
For example, an INR of 4 on co-therapy may not have the same
bleeding risk as an INR of 4 on warfarin monotherapy.
Continue anticoagulation for 2-3 months in HIT with out
thromboses but continue it for 6 months if a thrombotic event
occurred.
61. Guidelines for Conversion to Oral Anticoagulant Therapy
If INR is below the
therapeutic range
for warfarin alone,
resume Argatroban
therapy
If INR is >4.0, stop Argatroban infusion
Initiate warfarin therapy using the expected
daily dose of warfarin while maintaining Argatroban
infusion.* A loading dose of warfarin should not be used
If INR is within
therapeutic range
on warfarin alone,
continue warfarin
monotherapy
If INR is 4.0,
continue
concomitant therapy
Repeat INR 4-6 hours later
Measure INR daily
* For Argatroban infusion at 2 µg/kg/min, the INR on monotherapy may be estimated
from the INR on cotherapy. If the dose of Argatroban >2 g/kg/min, temporarily reduce
to a dose of 2 g/kg/min 4-6 hours prior to measuring the INR.
62. The Key to Avoiding Catastrophes from HIT is
Awareness, Vigilance, High Degree of Suspicion
When a patient...
+ experiences a drop in platelet counts
+ develops thrombosis
Consider HIT during/soon after
heparin exposure*
* Heparin exposure may be through virtually any preparation
(including LMWH), any dose, or any route of heparin
(including flushes and coated lines)
64. Differential Diagnosis of Thrombocytopenia
Clinical Setting – Cardiac Inpatients
HIT
Use of platelet GP IIb/IIIa-receptor
antagonists
Use of adenosine diphosphate-receptor
antagonists
Coronary-artery bypass grafting
Use of intra-aortic ballon pump
Aird AC, Mark EJ. N Engl J Med. 2002;346:1562-1570.
65. Clues to Diagnosis of HIT in
patients after Open-Heart Surgery
Prolonged thrombocytopenia
Rise in platelet count after surgery with subsequent fall
Multiple positive functional (SRA) and antibody
(ELISA) assay results
Unusual or unexpected thrombosis (may require
noninvasive testing)
Multiple thrombotic events
Systemic reaction shortly after heparin bolus
67. Immune Mediated Thrombocytopenia Purpura
(ITP)
Idiopathic ITP vs. Secondary ITP
Idiopathic or Primary ITP : Defined as isolated
thrombocytopenia with
Platelet count < 100 x 109/L
No other cause of thrombocytopenia
No clinically evident secondary form of thrombocytopenia.
High prevalence disease 16 to 27 per million per year
Incidence increases with age
Female predominance under the age of 60 but not over the age
of 60
May have onset or insidious onset generally abrupt in onset
with children and insidious in adults.
68. Pathogenesis of ITP
Increased platelet destruction caused by antiplatelet
antibodies antibodies directed against platetelet
membrane antigens such as GPIIb/IIIa the platelets
coated with immune complexes bind to Fc portion of
macrophages in spleen and other RES and are removed.
Lack of compensatory response by megakaryocytes due
to suppressive effect of antiplatelet antibodies
So, a combination of increased platelet destruction +
ineffective megakaryopoiesis.
Pathogenesis was proved by Harrington when he
infused himself with plasma from a women with ITP
( Harrington-Hollisworth Experiment)
69. Secondary ITP
Post-Infectious : HIV, HEP-C, H.PYLORI
Vasculitis : SLE
Lymphoproliferative Disorders : CLL, NHL, HD
Drug Dependant ITP (DDITP) : Drug induced TP can
be sometimes mediated by antibodies eg: quinidine,
sulfa containing drugs
72. *Platelets < 50 x 109/L
Study N ITP, n (%)
Murphy et al[1] 105 11 (10.5)
Kaslow et al[2] 1611 108 (6.7)
Rossi et al[3] 657 72 (10.9)
Peltier et al[4] 435 23 (5.5)
Mientjes et al[5] 285 67 (23.5)
Sloand et al[6] 1004 110 (11)
Sullivan et al[7] 30,214 1106 (3.7)*
Total 34,311 1497 (4.4)
1. Murphy MF, et al. Br J Haematol. 1987;66:337-340. 2. Kaslow RA, et al. Ann Intern Med. 1987;107:474-
480. 3. Rossi G, et al. AIDS Res Hum Retroviruses. 1990;6:261-269. 4. Peltier JY, et al. AIDS. 1991;5:381-
384. 5. Mientjes GH, et al. Br J Haematol. 1992;82:615-619. 6. Sloand EM, et al. Eur J Haematol.
1992;48:168-172. 7. Sullivan PS, et al. J Acquir Immune Defic Syndr Hum Retrovirol. 1997;14:374-379.
Therapeutic interventions: prednisone, anti-D, splenectomy, or HAART
Incidence of ITP in HIV
73. Evaluation of ITP
Features consistent with the diagnosis of ITP
Thrombocytopenia with normal or slightly large
platelets
( Increased MPV)
Normal RBC morphology and number (may have
associated iron def or thallasemia etc.)
Normal white cell number and morphology
Splenomegaly is extremely rare
Features not consistent with the diagnosis of ITP
Giant platelets ( ? Congenital)
RBC abnormalities ie schisotocytes ( ? TTP/HUS, DIC)
Leukocytosis or Leukopenia (? MPD/MDS, Sepsis )
74. Laboratory evaluation of ITP
Not Much !!!
No role for anti-platelet antibodies : many are highly
sensitive but they lack specificity.
Bone Marrow not very helpful as initial test
Helpful in patient over 50 years and concerned about MDS
If more than one cytopenia ( If not “isolated” TP)
If patient has failed initial treatment and diagnosis is in
question.
If abnormal forms on peripheral smear ( nucleated RBCs,
blasts)
TSH and HIV test helpful, HCV serology
Peripheral Smear helpful
75. Management of ITP
Most patients with ITP do not have clinically significant
bleeding
Risk of intracranial bleed 0.1 to 1% (This is an
overestimate)
Wet Purpura ie epistaxis, gingival bleeding is a risk factor
for major bleeding
Treatment is rarely indicated in patients with
platelet counts > 50 x 109/L.
In asymptomatic patients with platelets counts greater then
20 K observation is reasonable option. ( Wide range of
opinions on trigger platelet count at which Rx should be
initiated)
Patients with higher bleeding risk due to other factors may be chosen
for earlier treatment.
76. Timeline: introduction of modern day ITP drug treatment
Splenectomy
Corticosteroids
IVIg
Anti-D
Rituximab
TPO mimetics
1900 1920 1960 20001940 1980
77. Cines DB, et al. N Engl J Med. 2002;346:995-1008.
Pathophysiology of ITP – Intevention
Areas
78. Acute Pharmacologic Management of ITP
Steroids
Prednisone 1mg/kg/day with taper over 2 to 3 months
Solumedrol 30mg/kg/d x 7 days
Decadron
Antibodies
IVIG 1 gram/kg/day x 2 days
Anti-D 50 mcg/kg IV x1 dose in Rh+ patients
Binds to D antigen on erythrocytes that now bind to Fc
portions of macrophages saturating them Opsonized
erythrocytes compete with opsonized platelets for clearance by
macrophages.
IVIG vs. Anti-D : No definitive recommendations are made regarding the preferential use of one agent over another; both
agents have adverse events and even fatal events associated with their use. Anti-D may be associated with a longer duration of
response, whereas IV IgG may be preferred in patients with CVID. Consideration should be given to specific patient issues
such as age, comorbidities, renal function, and hemoglobin level in choosing which agent to use
80. Management of ITP
Selection of therapeutic option depends on :
– Urgency of platelet increase
– Tolerated toxicity by patient, eg, steroids
– Durability of effect
– Effect of thrombocytopenia and treatment on lifestyle and
profession ( ? people involved in contact sports etc)
81. Chronic Management of ITP
If no durable response or in non-responders :-
Splenectomy
Immunize with Pneumovax, Hib, Meningococcal
Chronic Anti-D therapy
Does not put the disease in remission
Rituximab
Eltrombopag ( c-MPL agnonists, TPO receptor
agonists)
Observation
82. Management of Adult ITP: Rituximab
Since previous consensus guidelines[1,2] were published, several studies
on the use of anti-CD20 therapy have been published
Approximately 60% of patients respond to rituximab treatment and
approximately 45% have a CR[3]; long-term responses (> 4 yrs) occur in 20%
of patients
The optimal dose of rituximab for ITP treatment is unknown and cases
of multifocal leukoencephalopathy have been reported, particularly in
patients who have been previously heavily immunosuppressed[4]
The drug may be more effective if used earlier in the course of ITP (
may save splenectomy)
1. George JN, et al. Blood. 1996;88:3-40. 2. British Committee for Standards in Haematology General
Haematology Task Force. Br J Haematol. 2003;120:574-596. 3. Arnold DM, et al. Ann Intern Med.
2007;146:25-33. 4. Provan D, et al. Blood. 2009;[Epub ahead of print].
83. Management of Adult ITP:
Thrombopoietin Receptor Agonists
Recent placebo-controlled randomized clinical trials have
demonstrated the utility of 2 thrombopoietin receptor agonists,
romiplostim and eltrombopag, in increasing platelet counts in
patients refractory to first- or second-line therapy[1,2]
These are maintenance agents that support a safe platelet count
but have no effect on the underlying ITP pathophysiology
However, the ability of these agents to increase platelet counts in
refractory postsplenectomy patients, allowing for reduction or
cessation of immunosuppressive agents, may make them the
treatment of choice in this patient population.
FDA approved for Chronic Refractory ITP.
1. Kuter DJ, et al. Lancet. 2008;371:395-403. 2. Bussel JB, et al. Lancet. 2009;373:641-648.
84. Immune Thrombocytopenia:
New definitions
Only patients who fail or relapse after splenectomy are considered as having refractory ITP.
Why: Splenectomy can induce a long-term unmaintained remission in > 60% of patients.
Quality of response
– CR: platelet count ≥ 100 x 109/L and absence of bleeding R: platelet count ≥ 30 x 109/L and at
least 2-fold increase the baseline count and absence of bleeding
– NR: platelet count < 30 x 109/L or less than 2-fold increase of baseline platelet count or
bleeding
Time to response: time from starting treatment to time of achievement of CR or R
Loss of CR or R: platelet count < 100 x 109/L or bleeding (from CR) or < 30 x 109/L or less than 2-fold
increase of baseline platelet count or bleeding (from R)
Timing of assessment of response to ITP treatments
– Variable, depends on the type of treatment
Duration of response
– Measured from the achievement of CR or R to loss of CR or R
– Measured as the proportion of the cumulative time spent in CR or R during the period under
examination as well as the total time observed from which the proportion is derived
Corticosteroid-dependence
– The need for ongoing or repeated doses administration of corticosteroids for at least 2 months
to maintain a platelet count at or > 30 x 109/L and/or to avoid bleeding (patients with
corticosteroid dependence are considered nonresponders)
Rodeghiero F, et al. Blood. 2009;113:2386-2393.
85. New Recommendations for ITP
Evaluation
Bone marrow aspirate and biopsy with flow studies for
patients older than 60 yrs[1]
Why: In addition to excluding underlying
myelodysplasia, flow studies may be helpful in
identifying patients with an ITP secondary to CLL[1]
Screen for HIV and HCV antibodies and assess H.
pylori infection by urea breath or stool antigen test[1]
Why: 4% to 30% of patients, depending on the
background infection rates in the local population, may
have ITP secondary to HIV, HCV, or H. pylori; treatment
of the primary chronic infection can result in an increase
in the platelet count[2]1. Provan D, et al. Blood. 2009;[Epub ahead of print]. 2. Cines DB, et al. Blood. 2009;113:6511-6521.
86. New Recommendations for ITP
Evaluation
Quantitative immunoglobulins[1]
Why: This test should be done before patients receive intravenous
immunoglobulins; this will reveal patients with CVID or IgA
deficiency
Direct antiglobulin test[1]
Why: A positive DAT was reported in 22% of 205 patients with
ITP[2]; important if patient has anemia and/or a high reticulocyte
count
Blood group Rh(D) typing[1]
Why: Important if treatment with anti-RhD immunoglobulin is
being considered; should be done in conjunction with DAT, since a
positive DAT may modify a decision to use anti-D therapy
1. Provan D, et al. Blood. 2009;[Epub ahead of print]. 2. Aledort LM, et al. Am J Hematol. 2004;76:204-213.
87. Management of ITP in pregnancy
Gestational Thrombocytopenia
Platelet count >70K, occurs late in gestation, not
associated with fetal thrombocytopenia, resolves after
pregnancy
ITP in pregnancy
Treat if symptoms - intermittent IVIG, Prednisone, anti-
D
Epidural anesthesia appears safe if platelet count > 50K
Monitoring for neonatal thrombocytopenia
88.
89. Practical Aspects for the management of
thrombocytopenia
What is an adequate platelet count for procedures?
“Platelet transfusion trigger”
Routine Dentistry >10K
Dental Extraction >30K
Regional Dental Block >30K
Minor Surgery >50K
Major Surgery>80K
Epidural anesthesia is okay at platelet count 50K for patient
with ITP
The target platelet count for a bleeding patient is
generally >50K
Prophylactic platelet transfusions for platelets < 10K
90. Prophylactic Versus Therapeutic Platelet
Transfusions
Platelet transfusions for active bleeding much more
common on surgical and cardiology services
Prophylactic transfusions most common on hem/onc
services
10 x 109/L has become the standard clinical practice on
hem/onc services
91. Platelet transfusions Source
Platelet concentrate (Random donor)
Each donor unit should increase platelet count ~10,000
/µl
Pheresis platelets (Single donor) ( Equal to 10 random
donor plt concentrates)
Storage
Up to 5 days at room temperature
92. Factors affecting a patients response to
platelet transfusion
Clinical situation: Fever, sepsis, splenomegaly,
Bleeding, DIC
Patient: alloimunization, underlying disease, drugs
(IVIG, Ampho B)
Length of time platelets stored ( shelf life)
15% of patients who require multiple transfusions
become refractory (alloimmunization)
93. Strategies to improve response to platelet
transfusions
Treat underlying condition
Transfuse ABO identical platelets
Transfuse platelets <48 hrs in storage
Increase platelet dose
Select compatible donor
Cross match
HLA match
94. Platelet transfusions - complications
Transfusion reactions
Higher incidence than in RBC transfusions ( febrile non-
hemolytic)
Related to length of storage/leukocytes/RBC mismatch
Bacterial contamination
TRALI
Post-Tranfusion Purpura
96. Inherited Thrombocytopenias – Mechanisms
Mutations in specific genes that play an important role
during the development of platelets or the cells that
make them, megakaryocytes.
Many forms but all of them are rare frequently
mistaken by physicians for something else, usually,
ITP.
97. Inherited thrombocytopenias – Clinical Spectrum
Ranges from severe bleeding diatheses recognized during
early weeks of life to mild forms that may remain
undetected even in adulthood
Diagnosis is difficult
Differentiating these ( especially the mild forms that are
detected in adults) from acquired thrombocytopenias,
especially ITP, is critical to avoid potentially harmful and
unnecessary treatments ( immunosuppressive therapes,
splenectomies)
98. Inherited thrombocytopenias –
Questions to help differentiate from immune/ acquired
etiology
Have the symptoms ( increased bleeding, bruising,
petechiae) been present for a long time?
Were platelet counts ever found to be low in the
past?
Are there any other family members who might
have similar symptoms or thrombocytopenia?
What has been the response to treatment? (
steroids, IVIG, Splenectomy)
Response to platelet transfusions (if required)?
99. Inherited Thrombocytopenias – Clues to
diagnosis
History : Chronicity of symptoms, age at
presentation, family history, other co-existent
symptoms ( hearing loss, immunodeficiency etc)
Mean Platelet Volume ( N = 7-11fl)
Peripheral smear - careful examination is
warranted for
Recognition of macro or micro thrombocytes will
narrow the differential
Presence of abnormal platelet granules
Neutrophil inclusions ( Dohle bodies)
Erythroid tear drop cells
Hairy cell leukemia
100. Peripheral blood platelets. (A) Normal blood smear (B) Macrothrombocyte. The platelet depicted (arrow) is larger than the average erythrocyte.
(C) Microthrombocytes (arrows) are typical of those seen in Wiskott-Aldrich syndrome or X-linked thrombocytopenia. (D) Döhle-like bodies in the
cytoplasm of neutrophils (arrows) are seen in the May-Hegglin anomaly. (Wright-Giemsa stain). Copied from 1. Drachman JG. Inherited
thrombocytopenia: when a low platelet count does not mean ITP. Blood 2004;103: 390-398
101. Inherited thrombocytopenias – Classification
Classified depending on:
the pattern of inheritance
the size of the platelets
whether or not there are other signs or symptoms that
are part of a syndrome.
102. Inherited Thrombocytopenias-Classification
Based on pattern of inheritance:
Autosomal Dominant
MYH9 related thrombocytopenias
Mediterranean macrothrombocytopenias
Velocardiofacial/DiGeorge Syndromes ( CATCH22)
Familial Platelet Disorder with Associated Myeloid Malignancy
(FPDMM)
Autosomal dominant Thrombocytopenia with linkage to Human
Chromosome2 ( THC2)
Paris Trousseau Thrombocytopenia
Gray Platelet Syndrome (GPS)
Autosomal Recessive
Congenital AMegakaryocytic Thrombocytopenia (CAMT)
Thrombocytopenia with Absent Radii (TAR)
Bernard-Soulier Syndrome (BSS)
X-linked Recessive
Wiskott-Aldrich Syndrome
X-linked Thrombocytopenia
GATA-1 Mutations ( X-linked Macrothrombocytopenia)
104. Mey-Hegglin Anomaly
1. First recognized in 1909
2. Diagnosis :
Mild to moderate thrombocytopenia, platelet
function is largely preserved
Macrothrombocytopenia with an MPV>11 fl
frequent giant platelets on peripheral smear
Dohle like cytoplasmic inclusions ( bluish
granules in neutrophilic cytoplasm with wright-
giemsa stain) in neutrophils
Absence of co-existing clinical features like
nephritis, sensori-neural hearing loss and
cataracts
MYH9 mutation on genetic testing
108. MYH9 Related Disorders - Therapy
Only mildly increased bleeding.
Usually diagnosed during routine testing of an
asymptomatic individual
Does not usually require therapy.
Educating the affected families (Inheritance pattern –
AD) about this diagnosis is paramount to avoid
potentially dangerous treatments for presumed ITP.
109. - Common in Southern Europe
- Very mild macrothrombocytopenia ( 70-150k)
- Giant platelets but largely preserved platelet function
- Gene Mutation – GP1BB (vWf Receptor)
- Chromosomal location – short arm of chr12.
111. CATCH22 Mild Macrothrombocytopenias
No serious bleeding
Characterized by cardiac abnormalities,
parathyroid and thymus insufficiencies, cognitive
impairment and facial dysmorphology
Deletion of GP1BB gene ( Chromosome location
22q11)
No need of therapy for these mild
thrombocytopenias however, recognize these
conditions to avoid unnecessary therapies.
113. FPDMM
Autosomal Dominant Inheritance.
Normal sized platelets
Striking predisposition for hematological malignancy.
Associated findings : AML, Myelodysplasia
Therapy: In view of high incidence of myeloid leukemia at a
young age (<60yrs), most patients will undergo stem cell
transplantation physician should be aware of FPDMM
so that mild thrombocytopenia in a HLA matched sibling
will not go unnoticed this is important as the recepient
may develop donor derived leukemia.
If AML1 mutation is identified in a pt with FPD/AML
must screen all potential sibling donors even if platelet
count is normal.
115. THC2
Mild thrombocytopenia
Normal sized platelets
Serious hemorrhage is rare
Megakaryocytes are present in bone marrow but are
small and have hypolobulated nuclei. ( unlike CAMT
where MKs are absent.)
No therapy is required. Again, recognition is
important to avoid unnecessary therapies.
117. Gray Platelet Syndrome
AD inheritance pattern
Macrothrombocytopenia
Absent alpha granules in the platelets giving a gray
color on wright-giemsa staining.
Mild bleeding risk.
118. Gene Mutation: MPL
Chromosome location: 1p34
Associated findings : severe marrow failure during 2nd
decade leading to pancytopenia
119. CAMT
Autosomal recessive inheritance both parents are
carriers and may have normal platelet number and
function.
Severe Thrombocytopenia in the neonates ( <10,000/ul,
MPV normal) secondary to ineffective megakaryopoeisis.
Recognized during first few days of birth due to easy
bleeding/bruising.
Diagnosis :
Severe Neonatal Thrombocytopenia
Absence of MKs in the bone marrow
Consider and rule out other differential diagnoses
Diagnosis is confirmed by molecular analysis of the MPL
gene.
Most severe form of CAMT is due to complete absence of
MPL receptor expression/function. Milder form is due to
residual activity of a mutant MPL receptor
120. CAMT
Course :
Severe CAMT is recognized during the first few days of birth due to easy
bleeding/bruising.
Milder form of CAMT is associated with low platelet number but sufficient to
prevent severe bleeding.
Mild form progresses to worsening thrombocytopenia by the first decade of
life. Also, associated with reduced leucopoeisis and erythropoeisis By the
second decade of life, can progress to pancytopenia.
When pancytopenia develops, CAMT may be confused with other marrow
failure disorders ( Aplastic Anemia, Fanconi anemia and Dyskeratosis
congenita)
Therapy:
Initial Rx : Platelet transfusion in neonates to prevent serious bleeding
Platelet increments and survival will be normal.
Platelet transfusion should be reserved for symptomatic patients to prevent
children from refractoriness because of alloimmunization.
HSCT ( Hematopoeitic Stem Cell Transplantation) should be considered as
soon as the diagnosis is confirmed and the donor has been identified.
121. Severe Neonatal Thrombocytopenia
Differential diagnosis
Congenital types
CAMT MKs (-) in bone marrow
TAR differentiating feature would be associated skeletal
hypoplasia of the arms. MKs + in bone marrow
WAS presence of microthrombocytes. MKs + in bone
marrow
Acquired types
Neonatal AlloImmune Thrombocytopenia (NAIT)
Resolves over several weeks as maternal antibodies are
cleared ( in contrast to CAMT that progresses). MKs + in
the bonemarrow.
Maternal transfer of antiplatelet antibodies ( in cases of
maternal ITP)
122. Neonatal AlloImmune Thrombocytopenia
A platelet analogue of the hemolytic disorder of the
newborn
Mechanism : Induced by feto-maternal alloimmunization
Women who lack common platelet antigens may
produce antibodies against paternal antigens that are
expressed in the developing fetus
NAIT typically associated with anti-HPA-1a antibodies
generated in response to fetal HPA-1a platelets in a mother
homozygos for HPA-1b phenotype.
Affects 1 in 1500 pregnancies. 50% occur during first
pregnancies ( unlike hemolytic disease of newborn)
Can lead to severe thrombocytopenia of fetus/ newborn
can manifest with intracranial bleeding.
123. Neonatal AlloImmune Thrombocytopenia
Therapy:
Maternal platelet transfusions ( HPA-1a negative)
to severely thrombocytopenic newborns.
IVIG and steroids to the neonate if
thrombocytopenia is life threatening and
persistent.
NAIT may persist for few weeks until all maternal
antibodies have cleared.
124. Thrombocytopenia with Absent Radii
Gene Mutation: unknown
Chromosome Location: unknown
Autosomal Recessive ( Parents usually
completely healthy)
125. TAR
Severe thrombocytopenia at birth Platelet
transfusions are frequently required in neonates
Normal sized platelets.
MKs present in bone marrow
Associated with skeletal anomalies shortened/
absent forearms due to defects in development of
bilateral radii.
Unlike CAMT, TAR will become less severe during
first year of life. Most affected people will not need
platelet transfusions after infancy.
127. Bernard-Soulier Syndrome
Mild lifelong macrothrombocytopenia (MPV>11 fl)
Bleeding tendency exceeds that predicted by degree of
thrombocytopenia.
Decreased expression of Vwf deficient binding of vWF
to the platelet membrane at sites of vascular injury,
resulting in defective platelet adhesion demonstrated by
the lack of aggregation of platelets in response to
ristocetin, an antibiotic that normally causes platelets to
aggregate deficient formation of the primary platelet
plug and increased bleeding tendency.
The cause of the thrombocytopenia is not definitely
known.
Questions remain!
Why does a defect in VWF receptor cause
macrothrombocytopenia?
Does the VWF receptor play a role in thrombopoeisis?
128. X-linked inheritance – common in males
Microthrombocytopenia
Gene Mutation: WAS
Chromosome Location: Xp
129. WAS
Almost exclusively affects male child
Moderate to severe Microthrombocytopenia ( 5k to 50k) in
the neonates ( very reduced MPV of 3.5-5.0 fl)
Associated Findings : Eczema, Immunodeficiency and
increased incidence of autoimmune diseases and
lymphomas.
Generally recognized in first year of life due to easy
bleeding/bruising as well as recurrent bacterial infections.
Diagnosis confirmed by genetic analysis of WAS
Mechanisms by which WAS mutation leads to
microthrombocytopenia not completely understood
MKs appear to be normal or increased in bonemarrow
suggesting a block during thrombopoeisis.
Also, both platelet size and number improve after
splenectomy suggesting the role of RES in platelet removal
( although no anti platelet antibodies have been detected)
130. WAS
Therapy:
Infections – MCC of death in WAS
IVIG ( IV gamma globulin) and broad spectrum antibiotics – Initial
therapies have increased median life expectancy of severe WAS
patients from 5yrs to 20yrs
Thrombocytopenia can be severe and lead to life threatening bleeding
Acute Rx involves platelet transfusions note that transfusions
provide normal increments and survival of circulating platelets.
Splenectomy can induce good increases in platelet counts. However,
should reserved for severe cases where HSCT is not feasible. Because
Splenectomy heavily increases risk of sepsis/infection in WAS. (In a
series of 39 patients, surgery normalized platelet count and
morphology in almost all cases, and the median survival of
splenectomized subjects was 25 years, compared with less than 5 years
in unsplenectomized ones. Ref: Mullen CA, Anderson KD, Blaese RM.
Splenectomy and/or bone marrow transplantation in the management
of the Wiskott-Aldrich syndrome: long-term follow-up of 62 cases.
Blood. 1993;82: 2961-2966 )
HSCT is the only curative therapy which corrects both
thrombocytopenia and immunodeficiency
133. GATA1 Mutation
X-linked thrombocytopenia which is
macrothrombocytopenia (MPV>11 fl)
Exclusively affects male children
Associated with mild to moderate dyserythropoeisis
leading to mild anemia.
Clinically, differentiated from WAS by presence of large
platelets and absence of WAS related associations.
Bone marrow is hypercellular with dysplastic features in
MK cell and erythroid lines but there is no progression
to myelodysplasia/ leukemia/bonemarrow failure
Thrombocytopenia is significant ( 10k to 40k) and can
sometimes lead to severe bleeding.
Confirmation is by sequencing of GATA1 gene
134. GATA1 Mutation
Therapy:
Therapeutic platelet transfusions ( in scenarios of
persistent bleeding and trauma/surgical
challenge)
HSCT is curative if anemia/thrombocytopenia
becomes life-threatening.
Future therapies may include repair of GATA1
mutation (gene therapy)
135. Role of Splenectomy in Congenital
thrombocytopenias
Definitive role has been established in WAS ( in cases
where HSCT is not feasible)
Different opinions in other inherited thrombocytopenias
(enclosed)
