Concomitant Granulomatosis with Polyangiitis and C3 Glomerulonephritis Causing Renal Failure.

A 75-year-old male with no prior history of vasculitis or renal deficiency presented with a history of 36 hours of anterior epistaxis, one month of worsening shortness of breath, severe anemia requiring transfusion, thrombocytopenia, coagulopathy with INR 4.9, and renal failure requiring hemodialysis. A peripheral blood smear revealed no evidence of microangiopathic hemolytic anemia. We performed an autoimmune workup, which revealed high levels of serum serine protease 3 antibody (C-ANCA), elevated rheumatoid factor, low serum C3, and normal levels of serum C4. We performed a renal biopsy and then performed light microscopy, immunofluorescence, and electron microscopy on the resulting samples. This revealed that approximately half of the sampled glomeruli were globally sclerotic, consistent with severe renal disease. Among the non-sclerotic glomeruli, several demonstrated diffuse granular mesangial staining for C3, while other glomeruli had small crescents, consistent with a mixed picture of C3 glomerulonephritis (C3GN) and crescentic glomerulonephritis. The patient responded well to treatment with cyclophosphamide and prednisone, with a resolution of his acute issues, significant improvement in kidney function, and was eventually weaned from routine hemodialysis. In summary, this is a unique case of a patient presenting with features of both granulomatosis with polyangiitis (GPA) and C3GN.