Table 1 Diagnostic Criteria for Schnitzler Syndrome*

Urticarial skin rash, monoclonal IgM component, and at least 2 of the following criteria:

Fever

Arthralgia or arthritis

Bone pain

Lymphadenopathy

Hepato- and/or splenomegaly

Elevated ESR

Leucocytosis

Abnormal findings on bone morphological investigations

*Another cause must be eliminated in all cases, most notably hyper IgD syndrome, AOSD, hypocomplementaemic urticarial vasculitis, acquired C1 inhibitor deficiency, and cryoglobulinaemia.