Anemia

Hemolytic anemias

Dr. Sura Obay Al-dewachi M.Sc Pathology/ Hematology

At the end of this lecture you will learn:

Definition of hemolysis and hemolytic anemia. Classification of hemolytic anemia. Immune hemolytic anemia definition and classification. Warm AB type immune hemolytic anemia. Cold AB type immune hemolytic anemia. Hemolytic disease of newborn. RH HDN Mechanical anemias

Hemolytic Anemia

Hemolysis is premature destruction of erythrocytes. When the life span of the red cells is shortened to less than 20 days, Hb drops and anemia develops (haemolytic anemia) Hemolysis is called intravascular when RBC destruction is in the circulation, while its called extravascular when destruction occurs by cells of the RES in the spleen, liver, and B.M.

Classification

I. H.A due to intrinsic red cell defects (usually inherited): Red cell membrane defects (e.g spherocytosis) Metabolic defect (enzymopathies: G6PD deficiency) Hb synthesis defect (hemoglobinopathies) II. H.A due to extrinsic red cells defects: Immune hemolytic anemia Mechanical hemolytic anemia H.A due to infection, chemical toxins.

Haemolytic Anaemias due to Extrinsic Factors

Immune hemolytic anemia (IHA)
Definition:Immune haemolysis is defined as destruction of red blood cells caused by antigen antibody reaction, antibodies are usually directed against red cell antigens. The defining character of all IHA is a positive Direct Antiglobulin Test ( DAT or Coomb’s test ) .


Classification
Autoimmune H. A.: Antibodies are directed against the person’s own RBCs. Warm antibody typeCold antibody type ( cold agglutinin syndromes)Alloimmune H.A : antibodies are produced against non-self antigens:Haemolytic disease of the newborn ( HDN).Hemolytic transfusion reaction.Drug induced IHA

Warm AB type AIHA

The antibody is IgG and has a maximal activity around 370C. All ages can be affected. Hemolysis is usually extravascular by the cells of the RE system mainly in the spleen. Females are affected more common. typically, the onset of symptoms is insidious over months. Jaundice , anaemia and splenomegaly. Haematologically: RBCs are normochromic, normocytic with spherocytosis, normoblastaemia and marked reticulocytosis.

Aetiology of warm type AIHA

Idiopathic in 30 % of cases. Secondary to another disease: Lymphoproliferative disorders ( CLL, HD and NHL ) Autoimmune disorders ( SLE, RA). Infections ( upper respiratory tract infection) malignancy ( ovarian ca. ) Drugs ( methyldopa )

Diagnosis of warm type IHA

Diagnosis depends on:Clinical findings.Classical red cell morphology.A positive direct Coomb’s testIf transfusion is needed, these patients present a problem to the blood bank as it is almost impossible to find a compatible blood, usually the least incompatible unit is chosen from a panel of blood units.

Cold AIHA

IgM antibodies Mainly seen in older people Detected by DCT It could be idiopathic or secondary to mycoplasma infection, lymphoma. Intravascular hemolysis.

Haemolytic Disease of the Newborn ( HDN )

Destruction of fetal RBCs by maternal AB. Maternal IgG AB can pass the placental barrier and react with fetal red cell antigens, more commonly with antigens in the ABO and Rh systems. ABO HDN it occurs mostly with babies whose mothers have O blood type and where the baby is either A or B type. Premature babies are much more affected than healthy full term babies. The disease is most commonly mild and Jaundice is the main clinical problem, rarely needs exchange transfusion,1st pregnancy can be affected.

Rh HDN ( Erythroblastosis fetalis )

This is the major cause of HDN, first born baby is not affected, but at the time of delivery fetal RBCs pass to maternal circulation and the mother may become sensitized ( produces anti-D antibodies ), the second baby will usually have severe anaemia with severe neonatal jaundice and may develop kernicterus with severe neurological defects unless promptly treated by exchange transfusion, subsequent deliveries result in still birth, the fetus has gross pallor, oedema , jaundice and gross abdominal distension with a bulky placenta ( hydrops fetalis ).


Rh HDN affects only about 30% of Rh-ve mothers carrying Rh+ve babies, ABO fetomaternal incompatibility reduces sensitization. The blood picture shows anaemia with reticulocytosis and normoblastaemia ( erythroblastosis fetalis ).

Mechanical anaemiasFragmentation Anaemias

Fragmentation anaemias are group of haemolytic anaemias characterized by presence of fragmented RBCs in the peripheral blood ( Schistocytes )and intravascular haemolysis.Fragmentation anaemias could result from:Prosthetic cardiac replacements ( valves and patches ), associated with turbulent blood flow ( cardiac haemolysis )Red cell destruction in the small blood vessels “ micro-angiopathic haemolytic anaemia ( MAHA ) “ as a result of :Wide spread fibrin deposition ( DIC ).

Abnormal platelet aggregation ( platelet aggregate syndromes ; HUS & TTP ). Abnormal vascular endothelium ( vasculitis ) MAHA is characterized by thrombocytopenia in addition to schistocytosis & features of intravascular haemolysis