Schnitzler syndrome complicated by membranous nephropathy.

Schnitzler syndrome is a rare clinical entity characterized by the association of chronic urticarial rash and monoclonal immunoglobulin M gammopathy. A 62-year old male developed nephrotic syndrome with Schnitzler syndrome. A renal biopsy revealed mild thickening of the glomerular basement membrane with spikes and mild expansion of the mesangial matrix; prominent fine granular immunoglobulin G depositions were found along the capillary walls by immunofluorescence study and electron dense deposits were observed in the subepithelial spaces and in a part of mesangium by electron microscopically. The histological findings were compatible with secondary form of membranous nephropathy. To the best of our knowledge this is the first renal biopsy case of Schnitzler syndrome. With corticosteroid treatment chronic rash and proteinuria have disappeared, but immunoglobulin (IgM) paraprotein has been still present.