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Urticarial skin rash1,2 and monoclonal IgM component3 and at least 2 of the following criteria4:
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Fever
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Arthralgia or arthritis
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Bone pain
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Palpable lymph nodes
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Liver or spleen enlargement
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Elevated ESR
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Leukocytosis
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Abnormal findings on bone morphologic investigations
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- Another cause must be eliminated in all cases (see differential diagnosis), most notably hyper IgD syndrome, adult onset Still disease, urticarial hypocomplementemic vasculitis, acquired C1 inhibitor deficiency and cryoglobulinemia.
- 1: the urticarial skin rash has now been extensively described and corresponds nosologically to a neutrophilic urticarial dermatosis [9]
- 2: some authors have reported patients with all signs of the Schnitzler but without the typical skin rash [8]; though those patients have probably a very similar disease, until further characterization, the peculiar skin rash should remain an obligate diagnostic criteria.
- 3: Some patients have a monoclonal IgG component instead of a monoclonal IgM [reviewed in [3]]
- 4: In patients treated with IL-1 inhibitors, a rapid and immediate response is supportive of the diagnosis. In case of unresponsiveness to anakinra, the diagnosis should be reconsidered.
