Two cases of atypical hemolytic uremic syndrome (aHUS) and eosinophilic granulomatosis with polyangiitis (EGPA): a possible relationship.

Atypical hemolytic uremic syndrome (aHUS) is a rare disease characterized by hemolysis, thrombocytopenia, and renal failure. It is related to genetic mutations of the alternative complement pathway and is difficult to differentiate from other prothrombotic microangiopathies. Eosinophilic granulomatosis with polyangiitis (EGPA) (Churg-Strauss syndrome, CSS) is a systemic ANCA-associated vasculitis and a hypereosinophilic disorder where eosinophils seem to induce cell apoptosis and necrosis and therefore, vasculitis. Here, we report the case of two CSS patients with a genetic complement disorder consistent with aHUS diagnosis. Both patients showed histologic features that supported the diagnosis of CSS, and a genetic complement study confirmed the suspected aHUS diagnosis. In the case where eculizumab was administered, the global response was excellent. There is very limited understanding of the genetics and epidemiology of both, atypical HUS and EGPA, but considering our two patients we suggest that an etiopathogenic link exists among patients diagnosed with both entities.