Table 1.

Etiology of abnormalities in the alternative complement pathway in TMA

aHUS is caused by mutations in complement protein genes or from the development of autoantibodies directed against FH. TA-TMA is associated with post-bone marrow transplant environmental stressors. CFHR1/CFHR3 indicate the deletions of complement factor H-related genes 1 and 3.

aHUS, mutations in complement genes	TA-TMA, environmental risk factors
Gain of function	Immunosuppressive drugs
C3	Total body irradiation
CFB	High-dose chemotherapy–conditioning regimens
Loss of function	Graft versus host disease
CD46	Infection
THBD	ABO incompatibility
CFI	Donor type
CFH
CFHR1/CFHR3 (deletion; plus autoantibody to FH)