Autoantibody Reactivity in a Case of Schnitzler’s Syndrome: Evidence for a Th1-Like Response and Detection of IgG2 Anti-FcεRIα Antibodies

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Abstract
Schnitzler’s syndrome is a rare disease characterized by chronic urticaria, monoclonal IgM, and clinical and laboratory signs of inflammation. In a subset of patients, the urticarial lesions cause pruritus. However, the pathophysiology of the disease and the biochemical basis of urticaria are not known. We describe a female patient with Schnitzler’s syndrome suffering from chronic urticaria associated with pruritus. The patient’s serum was found to contain IgG antibodies recognizing cellular components of the microvasculature. In particular, IgG3 antibodies directed against proteins (14–100 kD) expressed in cultured dermal microvascular endothelial cells and mast cells, were found by immunoblotting. Moreover, IgG2 antibodies specific for the α-chain of the FcεRI were detectable. However, the autoantibodies did not mediate histamine release in mast cells or basophils. In patients with IgM paraproteinemia who did not have Schnitzler`s syndrome, antibodies against endothelial/mast cells or FcεRI were not detectable. In summary, we describe subclass-specific IgG reactivity against microvascular endothelial cells and mast cells indicating Th1 autoimmunity in a patient with Schnitzler’s syndrome. Whether such autoantibodies are recurrently produced in patients with Schnitzler’s syndrome and play a role in the pathophysiology of the disease remains to be determined.

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