Another rare blood disorder that falls under the category of TMA (formerly named atypical hemolytic uremic syndrome (aHUS) is named: Complement-mediated HUS (CM-HUS). CM-HUS is a form of TMA that usually results from dysregulation of the alternative pathway of complement activation, resulting in the development of TMA findings and end organ injury of which renal injury predominates. CM-HUS can be triggered by infection, pregnancy and other causes of inflammation. Mutations of complement regulatory genes are found in more than half of patients with CM-HUS, but the presence of these mutations is not required for the diagnosis. Recent advances in the treatment of CM-HUS with an antibody that blocks complement activation have remarkably improved the prognosis of this disease.