The majority of cases are of the IgM-kappa isotype. There has been one case presented in the literature where the patient had clinical features of SS, but had an associated IgG, rather than IgM, gammopathy. Often, the areas of hyperostosis coincide with areas of symptomatic bone pain, such as the tibia, femur, ileum and vertebral columns. A small percentage demonstrated a superficial perivascular mononuclear infiltrate suggestive of chronic urticaria and lymphocytic inflammation. Vessels were intact, and there was dilatation of dermal lymphatics with mild superficial edema.
Rare cases show fibrin deposition, extravasation of erythrocytes or leukocytoclastic vasculitis.
Rarely were IgM deposits found within vessel walls. The urticarial eruption of SS is typically very resistant to treatment. However, no treatment is consistently effective. Skin and extracutaneous manifestations respond poorly to H1 and H2 antihistamines. Colchicine and dapsone have been tried with variable success in different patients.