Microangiopathic hemolytic anemia

In medicine (hematology) microangiopathic hemolytic anemia (MAHA) is a microangiopathic 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

It is referred as Runner's anemia. 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 fragmented resulting in intravascular hemolysis. The resulting schistocytes (helmet cells) are also increasingly targeted for destruction by the reticuloendothelial system in the spleen, due to their narrow passage through obstructed vessel lumina. It is seen in SLE because the immune complex aggregates with platelets, which creates intravascular thrombi.

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^{[citation needed]}:

• Aortic stenosis (most common cause of MAHA)^{[citation needed]}
• Malignant Hypertension
• Thrombotic thrombocytopenic purpura (TTP)
• Hemolytic uremic syndrome (HUS)
• Disseminated intravascular coagulation (DIC)
• HELLP syndrome and eclampsia
• Heparin-induced thrombocytopenia (HIT)
• Severe glomerulonephritis
• Signet ring cell carcinoma^[1]
• Several other rare causes

Pathophysiology

In all causes, the mechanism of MAHA is the formation of a fibrin mesh due to increased activation 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.

References

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