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Traumatic Hemolytic Anemia
(Microangiopathic Hemolytic Anemia)
Traumatic hemolytic anemia is intravascular hemolysis caused by excessive shear or turbulence in the circulation.
Trauma may originate
Outside the vessel, as in skeletal impact, eg, due to repetitive foot striking (march hemoglobinuria), a karate strike, or hand drumming
Within the heart across a pressure gradient, as in calcific aortic stenosis or due to a faulty aortic valve prosthesis
In arterioles, as in severe (especially malignant) hypertension, some malignant tumors, or polyarteritis nodosa
In end arterioles, often across fibrin deposits, as in thrombotic thrombocytopenic purpura and disseminated intravascular coagulation
The trauma causes odd-shaped RBC fragments (eg, triangles, helmet shapes) called schistocytes in the peripheral blood; their appearance on the peripheral smear is diagnostic. The small schistocytes cause low MCV and high RBC distribution width (the latter reflecting the anisocytosis).
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.
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