Diagnostic Considerations
Adult-onset Still disease is associated with fever, rash, arthralgias, and/or myalgias. The rash in Still disease is evanescent. The urticarial lesions in Schnitzler syndrome are chronically recurrent. In addition, monoclonal gammopathy does not occur in Still disease.
Systemic lupus erythematosus (SLE) may be associated with urticaria, fever, arthralgia, and an elevated ESR. However, leukopenia, neutropenia, and thrombocytopenia are seen in SLE, compared with the leukocytosis and thrombocytosis in Schnitzler syndrome. Antinuclear antibodies are present in SLE, but not in Schnitzler syndrome. Monoclonal paraprotein would not be expected in SLE.
Urticarial vasculitis can have features of nonpruritic urticaria persisting for more than 24 hours, myalgia, arthralgia, fever, an elevated ESR, and an increased white blood cell count. Skin biopsy of urticarial vasculitis shows fibrinoid necrosis of vessels and a perivascular neutrophilic infiltrate. Fibrinoid necrosis is rarely seen with Schnitzler syndrome.
Chronic idiopathic urticaria often responds symptomatically to antihistamines and lacks the accompanying systemic features and paraprotein seen in Schnitzler syndrome.
Cryoglobulinemia shows clinical signs and symptoms at cold temperatures and demonstrates the presence of cryoglobulins.
The cryoprin-associated periodic syndromes (CAPS), which include familial cold urticaria, Muckle-Wells syndrome, and chronic infantile neurologic cutaneous articular (CINCA) syndrome, all can have associated fever and rash. Patients with these disorders have onset before adulthood, lack a paraprotein, and have a family history of the disease. Muckle-Wells syndrome is often associated with amyloidosis and deafness. CINCA syndrome may be associated with chronic sterile meningitis and neurological deficits. [18]
Hyperimmunoglobulin D syndrome shows elevated polyclonal immunoglobulin D levels with onset of recurrent fever, usually in the first year of life.
Delayed pressure urticaria can occasionally be nonpruritic. However, it is not associated with an elevated ESR or an increased white blood cell count, although in severe cases, fever, myalgia, and arthralgias may occur. In addition, anemia is not seen with delayed pressure urticaria.
Waldenström macroglobulinemia shows a lymphoid proliferation in the bone marrow, and the monoclonal IgM gammopathy is found in large amounts, usually more than 10,000 mg/L. Often, it is associated with hepatosplenomegaly. In Schnitzler syndrome, the monoclonal gammopathy is less than that seen in Waldenström macroglobulinemia.
Differential Diagnoses
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Rash of Schnitzler syndrome. Courtesy of DermNet New Zealand (http://www.dermnetnz.org/assets/Uploads/systemic/schnitzler.jpg).
