Traumatic Hemolytic Anemia
(Microangiopathic Hemolytic Anemia)
(See also Overview of Hemolytic Anemia.)
Traumatic hemolytic anemia is intravascular hemolysis caused by excessive shear or turbulence in the circulation.
Trauma causes fragmented RBCs (eg, triangles, helmet shapes) called schistocytes in the peripheral blood; their appearance on the peripheral smear is diagnostic. Small schistocytes cause low MCV and high RBC distribution width (the latter reflecting the anisocytosis).
When RBC fragmentation occurs in the setting of microvascular injury, the process is termed microangiopathic hemolytic anemia (MAHA). 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, 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.