Complement alternative pathway activation in the course of thrombotic microangiopathy associated with adult-onset Still's disease.

Atypical haemolytic uraemic syndrome is a rare disease associated which genetic or acquired factors those cause defective regulation of the alternative complement pathway. We report the case of a 46-year-old woman who presented with thrombotic microangiopathy coinciding with a monocyclic evolution of adult-onset Still's disease. Low C3 with decreased FB concentration, associated with normal C4 was present until the thrombotic microangiopathy's resolution, indicative of an excessive production of alternative C3 convertase. She responded to plasma exchange. This observation reinforces the hypothesis for a common pathway in the pathogenesis for both of the diseases, and suggests alternative complement pathway mediation.