Microangiopathic hemolytic anemia

Overview
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 anemia and schistocytes on microscopy of the blood film.

Presentation
In diseases such as hemolytic uremic syndrome, disseminated intravascular coagulation, thrombotic thrombocytopenic purpura, as well as malignant hypertension, the endothelial layer of small vessels are damaged with resulting fibrin deposition and platelet aggregation. As red blood cells travel through these damaged vessels, they are shredded. The result is red cell fragmentation and intravascular hemolysis. Under the microscope, damaged red cells have the appearance of schistocytes.

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.

Causes
The most important causes are:
 * Aortic Stenosis (most common cause of MAHA)
 * Thrombotic thrombocytopenic purpura (TTP)
 * Hemolytic uremic syndrome (HUS)
 * Disseminated intravascular coagulation (DIC)
 * HELLP syndrome and eclampsia
 * Heparin-induced thrombocytopenia (HIT)
 * Severe glomerulonephritis
 * Several other rare causes

Pathophysiology
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.