Microangiopathic hemolytic anemia - Definition

In medicine (hematology) microangiopathic hemolytic anemia (MAHA) is a subgroup of hemolytic anemia (anemia, loss of red blood cells through destruction) caused by factors in the small blood vessels. It is identified by the finding of anaemia and schistocytes ("bite cells") on microscopy of the blood film.

Automated analysers (the machines that perform routine full blood counts in most hospitals) are generally programmed to flag blood films that display red blood cell fragments or schistocytes.

The most important causes are:

• Thrombotic thrombocytopenic purpura (TTP)
• Hemolytic uremic syndrome (HUS)
• Disseminated intravascular coagulation (DIC)
• HELLP syndrome and eclampsia
• Heparin-induced thrombocytopenia (HIT)
• Several other rare causes

In all causes, the mechanism of MAHA is the formation of a fibrin mesh due to increased activity of the system of coagulation. The red blood cells are physically cut by these protein networks, and the fragments are identical to the schistocytes seen on light microscopy.