hemolytic anemia (cell membrane defect)

Hemolytic Anemia

Dr. Rafi Ahmed GhoriFCPS

Professor MedicineLiaquat University of Medical & Health Sciences, Jamshoro

Classification of Hemolytic Anemias

1. Abnormalities of RBC interior1. Enzyme defects.2. Hemoglobinopathies

2. RBC membrane abnormalities1. Hereditary spherocytosis etc.2. Paroxysmal nocturnal hemoglobinuria.3. Spur cell anemia.

3. Extrinsic factor1. Hypersplenism.2. Antibody: immune hemolysis.3. Microangiopathic hemolysis.4. Infections, toxins, etc.

Intracorpuscular

Extracorpuscular

Hereditary

Acquired

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Red Cell Membrane Disorders

Usually detected by morphologic abnormalities of RBC on blood film.

Three types of inherited RBC membrane abnormalities– Hereditary sphercytosis.– Hereditary elliptocytosis (including hereditary

pyropoikilocytosis).– Hereditary stomatocytosis.

Red cell membrane has a lipid bilayer to which a ‘skeleton’ of filamentous proteins is attached via special linkage proteins.

RED CELL CYTOSKELETON

HEREDITARY SPHEROCYTOSIS

Defective or absent spectrin molecule Leads to loss of RBC membrane, leading to

spherocytosis Decreased deformability of cell Increased osmotic fragility Extravascular hemolysis in spleen

SPLENIC ARCHITECTURE

HEREDITARY SPHEROCYTOSISOsmotic Fragility

0

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0.3 0.4 0.5 0.6

NaCl (% of normal saline)

% H

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Normal HS

Hereditary Spherocytosis

Usually has an autosomal dominant inheritance pattern and incidence of approximately 1:1000 to 1:4500.

In ~20% patients, the absence of hematologic abnormalities in family members suggests either autosomal recessive inheritance or spontaneous mutation.


Sometimes clinically apparent in early infancy but often escapes detection until adult life.

Hereditary SpherocytosisClinical Manifestations

– Anemia.– Splenomegaly.– Jaundice.


– Prominent jaundice accounts for disorder’s prior designation as “congenital hemolytic jaundice” and is due to an increased concentration of unconjugated (indirect-reacting) bilirubin in plasma.


– Jaundice may be intermittent and tends to be less pronounced in early childhood.

– Due to increased bile pigment production, pigmented gallstones are common, even in childhood.

– Clinical course may be complicated by crisisHemolytic crisis (infection).Megaloblastic crisis (folate deficiency, especially in

pregnancy).Aplastic crisis (parvovirus infection).

Hereditary SpherocytosisDiagnosis

– Must be distinguished primarily from the spherocytic hemolytic anemias associated with RBC antibodies.

– If present, family history of anemia and/or splenectomy.

– Immune spherocytosis positive direct Coombs test.

Hereditary SpherocytosisDiagnosis

– Splenomegaly can also be seenCirrhosis.Clostridial infections.G6PD deficiency.


Treatment– Splenectomy reliably corrects the anemia.– Splenectomy in children should be postponed

until the age of 4-years.– Polyvalent pneumococcal vaccine should be

administered at least 2-weeks before splenectomy.

– In patients with severe hemolysis folic acid (5-mg/d) should be administered prophylactically.

Hereditary SpherocytosisTreatment

– Acute, severe hemolytic crises requires transfusion.

Hereditary ElliptocytosisHeterogeneous disorders in elliptocytic red

cells.Functional abnormality of anchor proteins

in red cell membrane (alpha spectrin or protein 4.1).

Autosomal dominant or recessive.Less common than hereditary spherocytosis

(1/10,000).

Red cell membrane has a lipid bilayer to which a ‘skeleton’ of filamentous proteins is attached via special linkage proteins.

Hereditary ElliptocytosisClinical presentation depends upon degree

of membrane defect.Asymptomatic diagnosed on blood film.Chronic compensated hemolytic state.

Hereditary ElliptocytosisTreatment

– Same as hereditary spherocytosis only in chronic hemolytic anemia.

Differential diagnosis includes– Iron deficiency anemia– Thalassaemia.– Mylofibrosis.– Mylodysplasia.– Pyruvate kinase deficiency.

Paroxysmal Nocturnal Hemoglobinuria

Clonal cell disorder Ongoing Intra- & Extravascular hemolysis; classically

at night Testing

– Acid hemolysis (Ham test)– Sucrose hemolysis– CD-59 negative (Product of PIG-A gene)

Acquired deficit of GPI-Associated proteins (including Decay Activating Factor)

GPI BRIDGE

Paroxysmal Nocturnal Hemoglobinuria

GPI Proteins

GPI links a series of proteins to outer leaf of cell membrane via phosphatidyl inositol bridge, with membrane anchor via diacylglycerol bridge

PIG-A gene, on X-chromosome, codes for synthesis of this bridge; multiple defects known to cause lack of this bridge

Absence of decay accelerating factor leads to failure to inactivate complement & thereby to increased cell lysis

HEMOLYTIC ANEMIAMembrane abnormalities -

Enzymopathies

Deficiencies in Hexose Monophosphate Shunt– Glucose 6-Phosphate Dehydrogenase Deficiency

Deficiencies in the EM Pathway– Pyruvate Kinase Deficiency

G6PD DEFICIENCYFunction of G6PD

G6PD

GSSG 2 GSH

NADPH NADP

2 H2O H2O2

6-PG G6P

Hgb

Sulf-Hgb

Heinz bodies

Hemolysis

InfectionsDrugs

Glucose 6-Phosphate Dehydrogenase

Functions

Regenerates NADPH, allowing regeneration of glutathione

Protects against oxidative stress Lack of G6PD leads to hemolysis during oxidative

stress– Infection– Medications– Fava beans

Oxidative stress leads to Heinz body formation, extravascular hemolysis

Glucose 6-Phosphate DehydrogenaseDifferent Isozymes

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RBC Age (Days)

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Normal (GdB) Black Variant (GdA-)

Mediterranean (Gd Med)

Level needed for protection vs ordinary oxidative stress

HEMOLYTIC ANEMIACauses

INTRACORPUSCULAR HEMOLYSIS– Membrane Abnormalities– Metabolic Abnormalities– Hemoglobinopathies

EXTRACORPUSCULAR HEMOLYSIS– Nonimmune – Immune

EXTRACORPUSCULAR HEMOLYSIS

Nonimmune

Mechanical Infectious Chemical Thermal Osmotic

Microangiopathic Hemolytic AnemiaCauses

Vascular abnormalities– Thrombotic thrombocytopenic purpura– Renal lesions

Malignant hypertension Glomerulonephritis Preeclampsia Transplant rejection

– Vasculitis Polyarteritis nodosa Rocky mountain spotted fever Wegener’s granulomatosis

Microangiopathic Hemolytic Anemia

Causes - #2

– Vascular abnormalities AV Fistula Cavernous hemangioma

Intravascular coagulation predominant– Abruptio placentae– Disseminated intravascular coagulation

IMMUNE HEMOLYTIC ANEMIAGeneral Principles

All require antigen-antibody reactions Types of reactions dependent on:

– Class of Antibody– Number & Spacing of antigenic sites on cell– Availability of complement– Environmental Temperature– Functional status of reticuloendothelial system

Manifestations– Intravascular hemolysis– Extravascular hemolysis

IMMUNE HEMOLYTIC ANEMIAGeneral Principles - 2

Antibodies combine with RBC, & either1. Activate complement cascade, &/or2. Opsonize RBC for immune system

If 1, if all of complement cascade is fixed to red cell, intravascular cell lysis occurs

If 2, &/or if complement is only partially fixed, macrophages recognize Fc receptor of Ig &/or C3b of complement & phagocytize RBC, causing extravascular RBC destruction

IMMUNE HEMOLYTIC ANEMIA

Coombs Test - Direct Looks for immunoglobulin &/or complement of

surface of red blood cell (normally neither found on RBC surface)

Coombs reagent - combination of anti-human immunoglobulin & anti-human complement

Mixed with patient’s red cells; if immunoglobulin or complement are on surface, Coombs reagent will link cells together and cause agglutination of RBCs

IMMUNE HEMOLYTIC ANEMIA

Coombs Test - Indirect

Looks for anti-red blood cell antibodies in the patient’s serum, using a panel of red cells with known surface antigens

Combine patient’s serum with cells from a panel of RBC’s with known antigens

Add Coombs’ reagent to this mixture If anti-RBC antigens are in serum, agglutination

occurs

HEMOLYTIC ANEMIA - IMMUNE

Drug-Related Hemolysis Alloimmune Hemolysis

– Hemolytic Transfusion Reaction – Hemolytic Disease of the Newborn

Autoimmune Hemolysis– Warm autoimmune hemolysis– Cold autoimmune hemolysis

IMMUNE HEMOLYSISDrug-Related

Immune Complex Mechanism– Quinidine, Quinine, Isoniazid

“Haptenic” Immune Mechanism– Penicillins, Cephalosporins

True Autoimmune Mechanism– Methyldopa, L-DOPA, Procaineamide, Ibuprofen

DRUG-INDUCED HEMOLYSIS

Immune Complex Mechanism

Drug & antibody bind in the plasma Immune complexes either

– Activate complement in the plasma, or– Sit on red blood cell

Antigen-antibody complex recognized by RE system Red cells lysed as “innocent bystander” of destruction

of immune complex REQUIRES DRUG IN SYSTEM


Haptenic Mechanism

Drug binds to & reacts with red cell surface proteins

Antibodies recognize altered protein, ± drug, as foreign

Antibodies bind to altered protein & initiate process leading to hemolysis


True Autoantibody Formation

Certain drugs appear to cause antibodies that react with antigens normally found on RBC surface, and do so even in the absence of the drug

ALLOIMUNE HEMOLYSISHemolytic Transfusion Reaction

Caused by recognition of foreign antigens on transfused blood cells

Several types– Immediate Intravascular Hemolysis (Minutes) - Due to preformed

antibodies; life-threatening– Slow extravascular hemolysis (Days) - Usually due to repeat

exposure to a foreign antigen to which there was a previous exposure; usually only mild symptoms

– Delayed sensitization - (Weeks) - Usually due to 1st exposure to foreign antigen; asymptomatic

INCOMPATIBLE RBC TRANSFUSIONRate of Hemolysis

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Normal Immediate Intravascular Hemolysis

Slow Extravascular Hemolysis Delayed Extravascular Hemolysis

ALLOIMMUNE HEMOLYSISTesting Pre-transfusion

ABO & Rh Type of both donor & recipient Antibody Screen of Donor & Recipient,

including indirect Coombs Major cross-match by same procedure

(recipient serum & donor red cells)

ALLOIMMUNE HEMOLYSISHemolytic Disease of the Newborn

Due to incompatibility between mother negative for an antigen & fetus/father positive for that antigen. Rh incompatibility, ABO incompatibility most common causes

Usually occurs with 2nd or later pregnancies Requires maternal IgG antibodies vs. RBC antigens

in fetus

ALLOIMMUNE HEMOLYSISHemolytic Disease of the Newborn -

#2

Can cause severe anemia in fetus, with erythroblastosis and heart failure

Hyperbilirubinemia can lead to severe brain damage (kernicterus) if not promptly treated

HDN due to Rh incompatibility can be almost totally prevented by administration of anti-Rh D to Rh negative mothers after each pregnancy

AUTOIMMUNE HEMOLYSIS

Due to formation of autoantibodies that attack patient’s own RBC’s

Type characterized by ability of autoantibodies to fix complement & site of RBC destruction

Often associated with either lymphoproliferative disease or collagen vascular disease

AUTOIMMUNE HEMOLYSISWarm Type

Usually IgG antibodies Fix complement only to level of C3,if at all Immunoglobulin binding occurs at all temps Fc receptors/C3b recognized by macrophages; Hemolysis primarily extravascular 70% associated with other illnesses Responsive to steroids/splenectomy

AUTOIMMUNE HEMOLYSISCold Type

Most commonly IgM mediated Antibodies bind best at 30º or lower Fix entire complement cascade Leads to formation of membrane attack complex,

which leads to RBC lysis in vasculature Typically only complement found on cells 90% associated with other illnesses Poorly responsive to steroids, splenectomy;

responsive to plasmapheresis

HEMOLYTIC ANEMIASummary

Myriad causes of increased RBC destruction Marrow function usually normal Often requires extra folic acid to maintain

hematopoiesis Anything that turns off the bone marrow can

result in acute, life-threatening anemia

hemolytic anemia (cell membrane defect)

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