09 Extrinsic Hemolysis

AIHA

• antibodies coat RBC. RBC removed in spleen

• RBC protect themselves from complement activation: no intravascular hemolysis

Warm

Pathogenesis and Symptoms

• classic symptoms of anemia

• splenomegaly: macrophages hypertrophy to consume RBCs

Diagnosis

• smaller, spherical, lack central pallor

• macrophage can't engulf whole RBC, just takes a bite off of it: shrink in size, more dense

• also inherited disease

• first see if normocytic anemia, then if RC is increased (increased production), then DAT

• anti IgG antibodies bind to IgG on RBC and cause them to agglutinate

• not used for AIHA

• take patient serum and add sample RBC. Positive if antibodies in patient serum to RBC

• used for new born hemolytic disease with mother serum against D+ RBC

Causes

• all these diseases involve immune system

• RBC bind antibody in absence of drug: surface of RBC altered

• also cephalosporin

Treatment

• severe: splenectomy

Cold

• symptoms of anemia plus symptoms in extremities

• large antibodies, cause RBC to agglutinate, especially in extremities

• IgM fix complement, leaves bound C3 on RBC

• DAT positive not for IgG but only for C3

• C3 doesn't get in the way of macrophages like IgG: engulf whole

• intravascular hemolysis result of complement activation

• instead of add IgG, add anti-C3

• IgG cold association with syphilis

MAHA

• intravascular hemolysis

• schistocytes: arrow, look like fragments

Mechanical

• very high BP causes endothelial damage

• thrombus shear RBC

• narrow openings, stiff tissues

Infections

• either intravascular RBC rupture or removal by spleen

• sickle: Higher risk of severe disease in sickle cell disease

• hole in robin's shirt: Higher risk of severe disease in asplenia

• cracked blood stained windows: Hemolytic anemia

• yellow babe: Jaundice

• Sweating robin: fever

• torn robin shirt: Irregularly cycling fevers