A case of chronic urticaria-like lesions with macroglobulinaemia (Schnitzler syndrome) is described. This case is unique by its double IgM monocomponents and by the follow-up study which shows immunoglobulins modifications between cutaneous flare-up and remission. As 1 case had a lymphoma, we studied the mononuclear cells of the bone marrow of Schnitzler syndrome to raise a possible malignant evolution of that disorder, and we discovered a hypodiploid population, which we compared with similar studies of myeloma and monoclonal 'benign' gammopathies.