IgG4-related disease with cutaneous manifestations treated with rituximab: case report and literature review.

Immunoglobulin type gamma 4 (Ig)G4-related disease (IgG4-RD) is a relatively recently described clinical entity characterised by elevated levels of serum IgG4 and tissue infiltration of IgG4+ plasma cells in various organ systems. Cutaneous involvement is rare but is becoming increasingly appreciated; typically presenting as erythematous papules and/or nodules that are commonly pruritic. We report a case of IgG4-RD presenting with persistent pruritic papules and unilateral parotid swelling. His serum IgG4 level was elevated and a histological examination of his skin biopsies found a lymphoplasmacytic infiltration with an excess of IgG4+ non-clonal plasma cells. The patient was intolerant of oral prednisolone, however complete resolution of the cutaneous lesions was achieved with the anti-CD20 antibody, rituximab.