Autoimmune hemolytic anemia

1. Immune Hemolytic Anemia

2. 1. Autoimmune Hemolytic Anemia (AIHA)
2. Alloimmune Hemolytic Anemia
-Hemolytic Transfusion reaction
-Hemolytic disease of the fetus & newborn
3. Drug-Induced immune Hemolytic Anemia

3. Autoimmune hemolytic anaemia

5. Warm Autoantibody Type

6. Pathophysiology
• IgG coated red cells bind to macrophages by
the Fc portion of the IgG.
• Phagocytosis of entire red cell occurs.
• More commonly, only a portion of the red cell
membrane is removed leading to the
formation of microspherocytes.
• These cells have decreased life span because
of their loss of plasticity & increased osmotic
fragility.

7. • Macophages have IgG Fc receptors only for
IgG1 & IgG3.
• Red cells coated with IgG1 alone require an
average of 2000 molecules to stimulate
phagocytosis
• Whereas only 230 molecules of IgG3 per red
cells are required for monocyte binding.

8. Clinical features
• Fatigue
• Palpitation
• Shortness of breath
• Splenomegaly :- only moderately enlarged, if
massive splenomegaly is present an underlying
lymphoproliferative disorder should be
considered.

9. Laboratory Features
• PBF show microspherocytes, polychromasia &
nucleated red cells.
• Presence of spherocytes indicate ongoing
hemolysis.
• Increased Reticulocyte count.
• Increased unconjugated bilirubin.
• Decreased serum hatpglobin.
• Hemoglobinemia, hemoglobinuria & urine
hemosiderin may be present.

10. Evan syndrome
• AIHA
• Autoimmune thrombocytopenia.
• Usually a complication of lymphoproliferative
disorder or collagen vascular disorder.

11. Antiglobulin
• Diagnosis usually depends on Positive DAT test.
• Indicate the presence of immunoglobulin or
complement or both on red cell surface.
• When test is positive, antiglobulin reagents specific
for IgG or C3 are used.
• In a study the frequency of
IgG alone 18-64%
IgG +C3 34-65%
complement alone 10-33%

12. Negative DAT Results In Patients with
Warm Type AIHA
• 2-4% of cases.
• Manually performed DAT requires about 300-
500 molecules of IgG per cell.
• Low levels can be detected using more
sensitive techniques like radioimmune assay &
Polybrene test.
• Use of anti IgA and anti IgM reagents to detect
IgA and IgM immunoglobulins.

13. Positive DAT Results in Patient without
Hemolytic anemia
• 1 in 14,00 healthy donors.
• Mainly IgG1.
• Complement alone is found in appro. 45% of
the healthy blood donors.
• Frequently found in patients receiving α-
methyldopa.

14. Concomitant Warm-Type & Cold-Type
AIHA
• DAT shows both IgG & C3.
• Cold agglutinin titer is usually high, >1:1000 at
4°c & the thermal amplitude is above 30°c.

15. Laboratory tests affected by warm antibodies
1. ABO Typing:- usually not affected.
2. Rh(D) Typing:-
- false positive result when RBCs are heavily
coated with IgG antibodies.
- decreased with use of monoclonal low
protein antisera.
- in extreme cases, EDTA/glycine acid
treatment of cells can be done to remove
antibodies.

16. • The major problem is the difficulty of cross
matchings.
• Because autoantibody may result in a positive
antibody screening test & incompatible cross
match.
• An alloantibody masked by the presence of the
autoantibody is the major concern.
• Red cell from the patients should be used to
adsorb the autoantibody from the patient’s
serum.
• Can be done only if the patient has not been
transfused in last 3 months.

17. • If he received transfusion recently, adsorption
with several heterologous cells or a cell
phenotypically matched to the patient may be
done.

18. Warm AIHA in children
• Peak incidence is in the first 4years of life.
• Can be
-acute, transient, self-limited disease
-prolonged chronic disorder
• Transient disease is more common, which often
follow well-defined viral illnesses.
• Patient usually recover in <3 months.
• DAT detects only complement in majority of the
cases.

19. Treatment
1. Transfusion:-
• Intravascular blood volume is typically normal
• Decision to transfuse is based solely on the
need to increase the oxygen-carrying capacity.
• Should be reserved for pt. at risk because of
underlying heart disease, cerebrovascular
ischemia, or life-threatening anemia.

20. 2. Glucocorticoids :-
• A short-acting glucocorticoid usually
prednisone is given.
• Most immediate action is to decrease red cell
destruction by interfering with monocyte-red
cell interaction in the spleen and liver.
• A later action is a reduction of the
autoantibody.
• It may also act by decreasing the binding
affinity of the autoantibody for red cell
antigens.

21. 3. Splenectomy :-
• Patient who has not initially responded to high
dose of glucocorticoids.
• Or subsequently requires >15-20 mg/day for
control of the hemolytic disease.
• Response is significantly better in patients with
idiopathic AIHA than in secondary cases.
• Removes the major site of red cell destruction
as well as a site for antibody production.

22. Other treatments
• Immunosuppresive therapy e.g. azathioprine,
cyclophosphamide & chlorambucil.
• Plasmapheresis is only a temporary method
because is only weakly effective in reducing
the level of IgG autoantibody in the plasma.

23. Cold Autoantibody Type
• React most strongly with red cells at 0-5°c
• Become clinically significant when their
thermal range of reactivity extends to 28-31°c
or higher.
• Temperature encountered in the
microvasculature of the skin, particularly in the
distal extremities, ears & the tip of the nose.

24. • Accounts for 15-25% of AIHA.
• Two types:-
1. Cold hemagglutinin disease
2. Paroxysmal Cold Hemoglobinuria

25. Characteristics Normal (Benign) cold
autoantibody
Pathological cold
autoantibody
Thermal range Below 20-24°C May be reactive at ≥30°C
Titer at 4°C ≤64 ≥1000
Reaction enhanced by none Albumin
Common antibody specificity Anti-I Anti-I rarely anti-I or anti-H
DAT Negative or weak pos. with
polyspecific AHG
Positive
Immunoglobulin class IgM IgM & rarely IgA or IgG
clonality Polyclonal Monoclonal when idiopathic,
Polyclonal when secondary to
infection
Clinically significant No Yes

26. Cold Hemagglutinin Disease
• Occurs in a transient or chronic form.
• Transient form occurs with mycoplasma
pneumonia or infectious mononucleosis.
• Primarily affect adolescents or young adults.
• Usually IgM.
• Chronic cold hemagglutinin disease (CCHAD)
usually affects persons >50yr of age.

27. Cold Agglutinins & Specificity
• Most often reactive with Ii blood group.
• The antibody is usually monoclonal IgM.
• Monoclonal IgM with Ƙ-light chains is usuallly
directed against the I antigen.
• Whereas IgM with ƛ-light chains are usually
directed against the I antigen.

28. • Cold agglutinins associated with Mycoplasma
pneumoniae pneumonia& infectous
mononucleosis are IgM and polyclonal.
• Cold agglutinin from mycoplasma infections
are usually reactive with I antigen
• Cold agglutinin from infectious mononucleosis
is often reactive with the i antigen.
• Other targets for cold hemagglutinins include
Pr; Gd, Sa, Lud & FI.
• Determination of specificity is generally not
necessary in clinial practice.

29. Pathophysiology
• Hemolytic potential depends on their titer & ability
to fix complement on red cell in vivo.
• Temperature in the superficial blood vessels of the
distal extremities range from 28-31°c.
• Lower temp. occurs with extremes of cold.
• At sites of lower temp., IgM react with red cells and
bind C1.
• Only a single molecule of IgM is required to bind C1
and initiate the activation of classical complement
pathway.

30. • C1 sequentially activates C4 & C2, which bind
to the red cells and form a C3 convertase
enzyme complex.
• As the blood returns to the warmer temp.
within the body, cold agglutinin dissociate
from the red cell membrane, but complement
activation continues.
• C3 convertase cleaves C3 to C3b & C3a.
• A single bind molecule of C3 convertase
enzyme complex can cleave several hundred
molecules of C3 to C3b.
• C3b binds to the red cell membrane.

31. • These cells are trapped predominantly in the liver.
• They bind to CR1 and CR3 complement receptors
on the hepatic macrophages.
• This results in phagocytosis of red cells.
• Patients with CCHAD develop a population of red
cells with normal survival.
• C3b is degraded to iC3b by factor I with factor H &
CrI as cofactors.
• Subsequently , iC3b undergoes a 2nd cleavage by
factor I to form C3dg, which is converted to C3d by
trypsin-like enzume.
• Macrophages do not recognize these breakdown
products and the red cells are released from the
liver.

32. Clinical Features
• Present with symptoms of chronic anemia.
• Patient may not acrocyanosis of their distal
extremities, nose, ears & chin on cold
exposure.
• Livedo reticularis, a sky-blue mottling of the
skin of the extremities, due to aggutination of
red cells impeding blood flow in the capillary
bed.

33. • Patinets with IgA monoclonal cold agglutinins
manifest acrocyanosis but no hemolysis,
because IgA does not activate the classic
complement pathway.

34. Laboratory Features
• Autoagglutination of the patien’s red cells at
room temperature.
• PBF shows polychromasia, agglutinated red
cells and some times spherocytes.
• Elevated reticulocyte count.
• An elevated MCV that corrects to normal on
heating the blood sample.
• Urine hemosiderin is of the prenesnt.

35. Antiglobulin Tests
• DAT shows C3 and more specifically, C3d.
• Healthy persons have low titer of IgM cold
agglutinins that usually do not exceed a titre of
I:64 at °c.
• The specificity of these cold agglutinis is
almost always anti-I.
• Pt. with pathologic cold agglutinins usually
have titers at 4 °c of 1:1000 or more in saline.

36. • If titer is <1:1000, a thermal amplitude test can
be performed.
• The patient’s serum is initially tested against
normal cells suspended in the saline at 20 °c.
• If positive, a test is performed at 30 °c in
albumin; a positive test indicates that the cold
agglutinin is of clinical importance.

37. Laboratory tests affected by cold
autoagglutinins
1. ABO Typing:-
• spontaneous agglutination an occurs if red cells
are heavily coated.
• Can be resolved by washing patient’s cells with
normal saline warmed to 37 °C.
2. Rh(D) Typing:-
• false positive result can be prevented by washing
the cells with normal saline
• Use of EDTA sample for grouping.

38. Treatment
• Usually anemia is mild and treatment is largely
symptomatic.
• Patients are advised to keep warm (particularly
extremities).
• Because of increased red cell turnover, folic acid
should be given.
• In severe cases chlorambucin or cyclophoshpamide
is given.
• Glucocorticoids and splenectomy generally are not
effective.

39. • Transfusion should be reserved for patients
whose cardiovascular or cerebrovascular
systems are significantly compromised.
• Washed RBC units are preferable, to avoid
supplying additional complement components.
• The blood should be infused through a blood
warmer, & the patient should be kept warm
during the transfusion.

40. Paroxysmal Cold Hemoglobinuria

41. • Rare form of AIHA
• Sudden onset of severe hemolysis particulary
after infection.
• Children are most commonly affected.
• First discovered by Donath & Landsteiner.
• Most often associated with congenital syphilis in
the past having a chronic course with
intermittent episodes of hemolysis.
• Today, encountered as an acute transient
hemolytic anemia in children after a variety of
infections.

42. Pathophysiology
• D-L autohemolysin is an IgG autoantibody.
• D-L antibody seldom binds to the red cell in
vitro at temperatures >20 °c.
• However, hemolysis occurs in these patients
even when they are not exposed to the cold,
indicating that the antibody is able to react at
higher temp. in vivo.
• The explanation for this paradox is not known.

43. • In most patients D-L antibody is IgG with anti-P
specificity.
• PCH is reported to be associated with a wide
variety of infections including:-
• Measles, mumps, CMV, chickenpox,
mycoplasma pneumonia, haemophilus
influenza, klebsiella pnumoniae & E. coli.

44. Clinical Features
• Acute attack typically occurs during the time a
patient is recovering from a recent URTI.
• Characterized by sudden onset of shaking
chills, back & leg pain, and abdominal cramps.
• Fever often follows.
• Fresh urine passed usually contains
hemoglobin.
• Symptoms usually subsides within a few hours.

45. • Attacks of PCH can be severe & life
threatening.
• Most patients recover in a few days to several
weeks without reccurence.
• Transient renal failure secondary to hemolysis
develops rarely.

46. Laboratory Features
• Features of hemolysis are seen during tha acute
attack.
• DAT result is positive for C3d.
• Biphasic D-L test:-
- patient’s serum is mixed with donor red cells &
fresh normal serum as a source of complement.
- the mixture is incubated at 4 °c, then warmed to
37 °c.
- hemolysis indicates the presence of D-L antibody.

47. Treatment
• Usually a self limiting disease.
• Pt. treated symptomatically by being kept warm.
• When transfusion is needed, P-positive red cells can
be given & are unlikely to precipitate hemolysis.
• Bloos is administered through a warmer.
• Glucocorticoid and splenectomy are usually not
effective.
• Although, syphilis is rarely a cause today, it should
be excluded in patients with chronic PCH.

48. Drug-Induced Hemolytic Anemia