Impairment of renal function in Schnitzler's syndrome.

The list of multisystem diseases involving both kidney and skin is long and includes immunologic disorders like systemic lupus erythematodes, a broad variety of vasculitides, metabolic disorders like diabetes mellitus, and infectious diseases. The present work describes the first case of renal failure due to Schnitzler's syndrome, a rare entity characterized by the association of generalized chronic urticaria, monoclonal IgM gammopathy, and osteosclerotic lesions. The described patient experiences improvement of renal function after treatment with the chimeric anti-CD20 antibody rituximab, indicating that the impairment of renal function might be mediated by B-lymphocytes. Renal insufficiency is known to be a potential complication of hypocomplementemic urticarial vasculitis. The present case reveals that it can occur in normocomplementemic urticarial vasculitides as well. Schnitzler's syndrome is a rare but probably underdiagnosed syndrome. It should be considered in the differential diagnosis of rash and coincidental renal failure of unknown origin. Immunofixation of immunoglobulins constitutes the crucial diagnostic step, since monoclonal gammopathy is a constant clinical sign in this entity.