M i c r o a n g i o p a t h i c H e m o l y t i c A n e m i a
Pathogenesis
Physical trauma to red cells (caused by fibrin strands or mechanical devices) causes red cells to get ripped apart.
Causes
Narrowing/obstruction of microvasculature (true microangiopathic hemolysis)
1. Disseminated intravascular coagulation (DIC)
• See in sepsis, abruptio placentae, many other clinical settings.
• Widespread clotting and bleeding.
• Get microthrombi, fibrin strands in vessels.
2. Thrombotic thrombocytopenic purpura (TTP)
• Syndrome consisting of MAHA, thrombocytopenia, CNS dysfunction,
renal failure and fever.
• Get microthrombi in vessels.
3. Hemolytic-uremic syndrome (HUS)
• Occurs usually in children, following infection with E. coli 0157
(symptoms: vomiting, bloody diarrhea).
• Syndrome consisting of acute MAHA and renal failure
(toxin produced by the bug damages endothelial cells).
• Get microthrombi in vessels.
4. Malignant hypertension (narrowed arterioles).
5. Systemic lupus erythematosus (necrotizing arteritis).
6. Disseminated malignancies (fibrin strands in vessels).
Heart/great vessel abnormalities (really "macroangiopathic" hemolysis)
1. Artificial heart valves.
2. Coarctation of aorta.
Morphology
• Schistocytes! Also, helmet cells, few spherocytes (from "rounding up" of
schistocytes).
• If also see thrombocytopenia, worry about DIC, TTP, or HUS.
Clinical features
• Symptoms vary according to cause of MAHA.
• The important thing is usually not the anemia itself, but the underlying
disorder! (Don't miss this one!)
