In diseases such as hemolytic uremic syndrome, disseminated intravascular coagulation, thrombotic thrombocytopenic purpura, and malignant hypertension, the endothelial layer of small vessels is 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 (red cell fragments) 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 systemic lupus erythematosus because the immune complex aggregates with platelets, which creates intravascular thrombi. Microangiopathic hemolytic anemia is also seen with cancer.
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.
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.