Cutaneous and systemic IgG4-related disease: a review for dermatologists.

Immunoglobulin G4-related disease (IgG4-RD) is a chronic inflammatory condition characterized by IgG4+ plasma cell infiltration of the skin and other organs. Cutaneous forms of the disease may be under recognized owing to poorly defined diagnostic criteria and relatively recent recognition in the literature. The aim of this review is to describe the clinical, histological, and serological presentations of cutaneous IgG4-RD, and to provide an overview of its systemic manifestations for dermatologists. Cases of cutaneous IgG4-RD identified in the literature review were compared to control cases. Clinically, plaque morphology and systemic involvement of the orbit, submandibular gland, lacrimal gland, and parotid gland were associated with a diagnosis of cutaneous IgG4-RD. Histologically, lymphoplasmacytic infiltrate and percentage of IgG4+ plasma cells/IgG+ plasma cells > 40% were associated with the diagnosis. Serologically, neither elevated serum IgG4 nor IgE concentrations were associated with the diagnosis. Dermatologists should consider IgG4-RD as part of the differential diagnosis for nodules, papules, and plaques with an IgG4+ plasma cell infiltrate, especially in middle-aged and elderly males with systemic manifestations of the disease. Diagnosis requires thorough investigation of both cutaneous and systemic clinical and histological presentations.