Microangiopathic hemolytic anemia is intravascular hemolysis caused by excessive shear or turbulence in the circulation.
(See also Overview of Hemolytic Anemia.)
Excessive shear or turbulence in the circulation causes trauma to red blood cells (RBCs) in the peripheral blood, leading to fragmented RBCs (eg, triangles, helmet shapes) called schistocytes (see photo Schistocytes). Schistocytes in the peripheral smear are diagnostic. Schistocytes cause high RBC distribution width, reflecting the anisocytosis.
Microangiopathic hemolytic anemia encompasses RBC fragmentation caused by microvascular injury as well as by mechanical devices. Causes of fragmentation hemolysis include
Disseminated intravascular coagulation, a consumptive process secondary to other disorders such as sepsis, malignancy, pregnancy complications, trauma or surgery
Stenotic or mechanical heart valves, or prosthetic valve dysfunction (ie, perivalvular leak)
Hemolytic uremic syndrome or related disorders such as the HELLP syndrome (hemolysis, elevated liver enzymes, and low platelet count), and systemic sclerosis renal crisis
Rare cases of significant repetitive impact, such as foot strike hemolysis (march hemoglobinuria), karate strikes, swimming, or hand drumming
Treatment addresses the underlying process. Iron deficiency anemia occasionally is superimposed on the hemolysis as a result of chronic hemosiderinuria and, when present, responds to iron-replacement therapy. Keeping the hematocrit > 30 % can reduce hemolysis caused by turbulent flow.
