The document discusses thrombotic thrombocytopenic purpura (TTP), highlighting its symptoms, such as anemia and thrombocytopenia, and the genetic mechanisms involved, specifically mutations in the ADAMTS13 gene leading to a deficiency in von Willebrand factor-cleaving protease. It provides case studies of patients with TTP, treatment responses, and the importance of plasma infusion in managing the condition. Key diagnostics for TTP include low ADAMTS13 activity and characteristic blood smear findings.

1. Thrombotic Thrombocytopenic Purpura (TTP)
TTP (MIM#274150); ADAMTS13 (MIM#604134)
Abdul-Kader Souid9/26/2018 1
“Microangiopathic Hemolytic Anemia + Thrombocytopenia (e.g., TTP, HUS, DIC)”
TTP (↑vWF) = Microangiopathic hemolytic anemia + Thrombocytopenia + CNS injury
Moake JL. Thrombotic microangiopathies. N Engl
J Med. 2002;347:589-600. PMID: 12192020.

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4. Patient
• A 12-year-old boy has anemia and thrombocytopenia.
– ↓Hemoglobin, ↑reticulocyte count, ↑RBC fragments (schistocytes), and
hemoglobinuria → intravascular hemolysis.
• His thrombocytopenia responded to plasma transfusion.
• He then had recurrent seizures.
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Black arrows point to RBC fragments, red arrow points to a
large platelet, and blue arrow to a spherocyte.

5. His CBC
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Anemia + thrombocytopenia + reticulocytosis

6. His Peripheral Blood Smear
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Microangiopathic hemolysis
Arrows point to RBC fragments

7. His Urinalyses (UA)
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Hemoglobinuria
Urine is free of RBC

8. von Willebrand factor-cleaving protease (VWFCP) deficiency → TTP
• Autosomal recessive disease
• Intravascular (microangiopathic) hemolysis
• Consumptive thrombocytopenia
• The pathologic process is reversed by plasma infusion
• Seizure disorder
3) Factor VIII delivery
1) Platelet adhesion to collagen
2) Platelet-platelet spreading and aggregation
Collagen
vWF
GPIb-
Platelet
GPIIb/IIIa
vWF
Fibrinogen
Platelet
Factor VIII
-S-S-
-S-S-
Results of his work-up:
• von Willebrand factor-cleaving protease (VWFCP) activity <5% (normal, ≥67%)
• VWF antigen and activity are normal.
• VWF Multimer Analysis = ↑molecular weight multimers

9. • Von Willebrand factor (VWF) is a multimeric plasma glycoprotein that mediates
platelet adhesion and aggregation.
• ADAMTS13 is a protease that cleaves VWF in circulating blood and thereby
limits platelet aggregation.
Familial Thrombotic Thrombocytopenic Purpura =
von Willebrand Factor-Cleaving Protease Deficiency =
ADAMTS13 Deficiency
• His ADAMTS13 gene sequencing shows homozygous splice site mutation,
c.2234+2T>C in ADAMTS13.
• ADAMTS13: “A Disintegrin-like and metalloproteinase with thrombospondin
type 1 motif, member 13”.
• ADAMTS13 gene is located at: 9q34.2. MIM#604134
(http://omim.org/entry/604134)

10. • In patients with TTP, abnormally large VWF multimers in
the plasma cause excessive intravascular platelet
aggregation.
• These extremely adhesive VWF multimers arise due to a
deficiency of VWF-cleaving protease.
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Blood 1997;89:3097-3103
Familial Thrombotic Thrombocytopenic Purpura =
von Willebrand Factor-Cleaving Protease (VWFCP) Deficiency =
ADAMTS13 Deficiency

11. • All studied six patients with familial TTP lacked vWF–cleaving protease
activity, but had no inhibitor.
• Of studied 24 patients with non-familial TTP, an inhibitor (IgG) of vWF–
cleaving protease was found in 20 of these patients.
• All 10 patients with familial HUS had normal protease activity.
• All 13 patients with non-familial HUS had normal or slightly protease
activity.
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NEJM 1998;339:1578-1584
Familial Thrombotic Thrombocytopenic Purpura =
von Willebrand Factor-Cleaving Protease (VWFCP) Deficiency =
ADAMTS13 Deficiency

12. • Mutations in a member of the ADAMTS gene family cause thrombotic
thrombocytopenic purpura.
• Proteolysis of VWF observed in normal plasma is decreased in TTP patients.
• In four pedigrees of humans with congenital TTP, the responsible protease was mapped to
chromosome 9q34.
• A predicted gene in the identified interval corresponded to a new member of the ADAMTS
family of zinc metalloproteinase genes (ADAMTS13).
• Analysis of patients' genomic DNA identified 12 mutations in the ADAMTS13 gene,
accounting for 14 of the 15 disease alleles studied.
• Deficiency of ADAMTS13 is the molecular mechanism responsible for TTP.
• Physiologic proteolysis of VWF and other ADAMTS13 substrates is required for
normal vascular homeostasis.
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Familial Thrombotic Thrombocytopenic Purpura =
von Willebrand Factor-Cleaving Protease (VWFCP) Deficiency =
ADAMTS13 Deficiency
Nature 2001;413:488-94.

13. Familial Thrombotic Thrombocytopenic Purpura
von Willebrand Factor-Cleaving Protease (VWFCP) Deficiency
ADAMTS13 Deficiency
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Day Treatment
Hemoglobin
(g/L)
Platelet
count
(x109/L)
Hemoglobinuri
a
ADAMTS13
activity
-1 - 100 99 Small <5%
0 Plasma 10.9 118 Small 19
1 - 10.3 103 Small 31
6 - 11.8 203 Negative 12
8 - 11.9 264 Negative 18
10 - 11.8 188 Negative <10
17 - 11.6 114 Trace <10
20 - 11.0 33 Large <10
22 Plasma 10.7 22 Moderate 23
Plasma infusion every two weeks is recommended as the treatment
of choice.

14. A 17-year-old girl presents with pallor, bruising and seizure. Her examination shows significant
pallor and purpura. Her lymph nodes, liver, and spleen are normal.
Her WBC count is 8 x109/L (normal, 5 to 10), hemoglobin concentration 73 g/L (normal, 110 to
130), reticulocyte count 318 x109/L (normal, 35 to 100), and platelet count 65 x109/L (normal, 150
to 400). Blood smear shows numerous schistocytes with a markedly reduced number of platelets.
PT/INR, aPTT, TT, fibrinogen, and D-Dimer level are normal.
Her serum creatinine is normal. Her urinalysis is remarkable for 2 RBC per high power field
(normal, <5) and 3+ hemoglobin (normal, negative).
She received plasma infusion, which promptly improved her thrombocytopenia.
Which one of the following results on further investigation is correct?
A. Complement dysregulation (hemolytic uremic syndrome)
B. Mutation in ADAMTS13 gene (thrombotic thrombocytopenic purpura)
C. Low von Willebrand factor (VWD)
D. Positive direct antiglobulin test for IgG (autoimmune hemolytic anemia)
E. Missing CD59 on the surface of blood cells (paroxysmal nocturnal hemoglobinuria)
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15. Which one of the following diagnoses is correct?
A. Macrophage activation syndrome (MAS)
B. Hemolytic uremic syndrome (HUS)
C. Thrombotic thrombocytopenic purpura (TTP)
D. Hemophagocytic lymphohistocytosis (HLH)
E. Disseminated intravascular coagulopathy (DIC)
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A 17-year-old girl presents with pallor, bruising and seizure. Her examination shows significant
pallor and purpura. Her lymph nodes, liver, and spleen are normal.
Her WBC count is 8 x109/L (normal, 5 to 10), hemoglobin concentration 73 g/L (normal, 110 to
130), reticulocyte count 318 x109/L (normal, 35 to 100), and platelet count 65 x109/L (normal, 150
to 400). Blood smear shows numerous schistocytes with a markedly reduced number of platelets.
PT/INR, aPTT, TT, fibrinogen, and D-Dimer level are normal.
Her serum creatinine is normal. Her urinalysis is remarkable for 2 RBC per high power field
(normal, <5) and 3+ hemoglobin (normal, negative).
She received a fresh frozen plasma infusion, which promptly improved her thrombocytopenia.

16. Which one of the following treatments is correct?
A. Eculizumab (for HUS and PNH)
B. Packed red cell transfusion (for AHA)
C. Platelet transfusion (for bone marrow failure syndromes)
D. Plasma exchange (for TTP and HUS)
E. Immunoglobulin transfusion (for ITP)
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A 17-year-old girl presents with pallor, bruising and seizure. Her examination shows significant
pallor and purpura. Her lymph nodes, liver, and spleen are normal.
Her WBC count is 8 x109/L (normal, 5 to 10), hemoglobin concentration 73 g/L (normal, 110 to
130), reticulocyte count 318 x109/L (normal, 35 to 100), and platelet count 65 x109/L (normal, 150
to 400). Blood smear shows numerous schistocytes with a markedly reduced number of platelets.
PT/INR, aPTT, TT, fibrinogen, and D-Dimer level are normal.
Her serum creatinine is normal. Her urinalysis is remarkable for 2 RBC per high power field
(normal, <5) and 3+ hemoglobin (normal, negative).
She received plasma infusion, which promptly improved her thrombocytopenia.

17. Which one of the following managements is correct?
A. Stool studies for Escherichia coli serotype O157:H7
B. Monitor hemoglobin concentration, platelet count, and serum creatinine
C. Platelet transfusion
D. Packed red blood cell transfusion
E. Plasma exchange
17
A 17-year-old girl presents to the emergency department with pallor, fatigue and abnormal
bruises. Her examination shows significant pallor, mild jaundice, and ecchymosis mostly in her
extremities. Her lymph nodes, liver, and spleen are normal.
Her WBC count is 8 x109/L (normal, 5 to 10), hemoglobin concentration 73 g/L (normal, 110 to
130), reticulocyte count 318 x109/L (normal, 35 to 100), and platelet count 65 x109/L (normal, 150
to 400). Blood smear shows schistocytes with decreased number of platelets. PT/INR, aPTT, TT,
fibrinogen, and D-Dimer level are normal.
Her serum creatinine is normal. Her urinalysis is remarkable for 2 RBC per high power field
(normal, <5) and 3+ hemoglobin (normal, negative).

18. Required Reading
• George JN. Clinical practice. Thrombotic thrombocytopenic
purpura. N Engl J Med 2006;354:1927.
• George JN. How I treat patients with thrombotic
thrombocytopenic purpura: 2010. Blood 2010;116:4060.
• Levy GG, Nichols WC, Lian EC, et al. Mutations in a member of
the ADAMTS gene family cause thrombotic thrombocytopenic
purpura. Nature 2001;413:488.
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