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.