Malignant evolution of Schnitzler's syndrome--chronic urticaria and IgM monoclonal gammopathy: report of a new case and review of the literature.

Schnitzler's syndrome, initially described in 1974 is an uncommon condition defined by chronic urticaria and monoclonal IgM gammopathy. Additional features include fever of unknown origin, elevated ESR, bone pain and frequently a benign clinical course. We conducted a literature search of Medline, EMBASE and Cancerlit and found 56 cases of Schnitzler's syndrome reported to date. The absence of lymphoproliferative disease in this condition is typical, but nine patients have progressed to develop lymphoplasmacytic neoplasias, particularly Waldenstrom's macroglobulinemia (WM). Malignant evolution of Schnitzler's syndrome is a rare complication, but emphasizes the importance of long term follow-up and the need for these patients to undergo periodic assessment of the bone marrow and lymph nodes. Treatment of this condition is difficult, with varying response to corticosteroids and largely unsuccessful results with standard chemotherapy used for WM. We describe a case of Schnitzler's syndrome in a 50-year old man with lymphocytic aggregates in the bone marrow after 9 years of chronic urticaria, fever, arthralgias and bone pain. We review the clinical features and treatment, with emphasis on the hematologic aspects of this unusual condition.