Investigations of IgG4-related disease involving the skin

Objectives: IgG4-related skin disease is not widely recognized. This prompted us to investigate the clinical and pathological features of five patients we encountered with IgG4-related disease (IgG4-RD) affecting the skin. Methods: We investigated the clinical and pathological features of these five patients, including the distribution, onset, and morphology of eruptions, their pathological and immunohistochemical characteristics, and the occurrence of disease in other organs. Results: The skin lesions were typically erythematous nodules and papules and brown papules like prurigo nodularis, which developed on the face or in the head and neck areas in four patients. Skin lesions were the first clinical manifestation in three patients. All five patients had sialadenitis and/or dacryoadenitis. The mean serum IgG4 concentration was 665.6 ± 410.0 mg/dl. Infiltrations of IgG4-positive plasma cells were observed in both the dermis and subcutaneous tissue. Germinal center formations were seen in three patients. Mild to moderate fibrosis was observed in all patients, and focal obliterative phlebitis in one. The average count of IgG4-positive cells was 67.3/high-power field (23.0-128.6). Wide variation in the numbers of infiltrating IgG4-positive cells was noted. Conclusion: IgG4-RD appears to have a distinctive clinicopathological presentation in the skin, differentiating it from other cutaneous disorders.