Immunoglobulin G4-related disease presenting with prurigo: Circulating T-helper 2 cells may be involved in the pathogenesis.

We report a case of immunoglobulin G4-related disease (IgG4-RD) which presented with prurigo on the trunk and extremities. A 66-year-old man had a 2-month history of itchy erythematous papules on his trunk and extremities. Bilateral eyelid swelling and enlargement of the submandibular and parotid glands were also observed. Computed tomography revealed pleural thickening and diffuse pancreatic enlargement. Serum levels of IgG4 were markedly increased. A biopsy specimen obtained from an erythematous papule showed a perivascular inflammatory infiltrate of lymphocytes with eosinophils in the dermis, whereas a parotid gland biopsy revealed an infiltrate of abundant IgG4-positive plasma cells. Treatment with prednisolone resulted in improvement of the skin and other lesions along with a decrease in IgG4 serum levels. A flow cytometric assay revealed that percentages of interleukin (IL)-4- and IL-13-producing CD4(+) T cells were markedly higher in the circulation of the IgG4-RD patient than in that of healthy subjects. Moreover, those populations dramatically decreased after treatment. Thus, prurigo may be a skin manifestation of IgG4-RD and T-helper 2 cells may contribute to the pathogenesis.