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