Schistocytes (helmet cells)

Definition:

Schistocytes are erythrocyte fragments which are formed by mechanical action in small, damaged vessels, or by artificial cardiac valves. They are of variable shapes, typically however, half-moon or dough nut-shaped.

Occurrence:
Schistocytes are, if not otherwise explicable (artificial cardiac valves and March hemoglobinuria), an alarming abnormality. They can be found in the following states with microangiopathic hemolytic anemia (MAHA):

• Thrombotic thrombocytopenic purpura (TTP)
• Hemolytic uremic syndrome (HUS), e.g. by enterohemorrhagic E. coli (EHEC)
• Disseminated intravascular coagulation (DIC)
• Severe burns