A 50-year-old man presented with a 6-year history of episodes of simultaneous fever, arthralgia and rash, the latter being widespread, mildly pruritic and urticarial. No lymph node, hepatic or splenic enlargement was found. Laboratory investigations showed only increased levels of C-reactive protein and a monoclonal immunoglobulin (Ig) Mκ component (0·01 g/l). Urine was negative for Bence-Jones protein. A bone marrow aspirate showed normal haematopoiesis and plasma cells were approximately 10%. On the basis of the clinical and laboratory features, a diagnosis of Schnitzler syndrome was made.
Only about 80 cases of Schnitzler syndrome have been reported to date. This little known and very likely under-recognized syndrome is characterized by the simultaneous occurrence of monoclonal gammopathy and chronic urticaria with additional features such as arthralgia, bone pain, recurrent fever, lymphadenopathy and hepatosplenomegaly being sometimes present. The aetiology is unclear. A pathophysiological role for interleukin-1 has been suggested.