Hypertension-associated thrombotic microangiopathy in an adult patient with complement factor H autoantibodies and a rare heterozygous variant in the gene.

Atypical hemolytic uremic syndrome (aHUS) is a rare disease characterized by microangiopathic hemolytic anemia, thrombocytopenia, and renal injury, which results from thrombotic microangiopathy (TMA) within the glomerular capillaries and arterioles. We report a case of a biopsy-proven renal TMA attributed to hypertension in a 42-year-old woman with undiagnosed alternative complement pathway dysregulation resulting from a rare association between complement factor H (CFH) autoantibodies and a heterozygous variant in the gene. We propose that severe hypertension triggered an over-activation of the alternative complement pathway in a patient with genetic predisposition. In this case, blood pressure control allowed normalization of hematologic parameters and partial recovery of renal function, supporting the idea that shear stress is an important complement-amplifying factor.