Merck Manual

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Microangiopathic Hemolytic Anemia

(Traumatic Hemolytic Anemia)


Evan M. Braunstein

, MD, PhD, Johns Hopkins University School of Medicine

Last full review/revision Jun 2022| Content last modified Sep 2022
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Microangiopathic hemolytic anemia is intravascular hemolysis caused by excessive shear or turbulence in the circulation.

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 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

Treatment addresses the underlying process. Iron deficiency anemia Iron Deficiency Anemia Iron deficiency is the most common cause of anemia and usually results from blood loss; malabsorption, such as with celiac disease, is a much less common cause. Symptoms are usually nonspecific... read more 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.

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