Isolated cutaneous manifestation of IgG4-related disease

Aims The cutaneous manifestation of IgG 4 -related disease has rarely been reported. The aim of this study is to identify and describe the cutaneous manifestations associated with IgG 4 -positive plasma cell infiltration in the skin. Methods The authors investigated two cases of IgG 4 -related disease with solitary skin lesions and compared the immunohistochemical characteristics of infiltrating cells among IgG 4 -related disease, Kimura9s disease and cutaneous pseudolymphoma. Results IgG 4 -related disease manifested as an indurated plaque on the anterior chest in one case and a nodule on the toe in the other case. Histopathologically, skin lesions of IgG 4 -related disease showed a dense, mixed-cell infiltrate containing lymphocytes, plasma cells and eosinophils along with fibrosis. Plasma cells stained positively with anti-IgG and anti-IgG 4 antibodies, and the ratio of IgG 4 +/IgG+ cells was more than 50%. Serum levels of IgG and IgG 4 were not elevated and no lesions were found in other organs. Skin samples taken from Kimura9s disease showed histopathological features similar to those of IgG 4 -related disease. The proportion of IgG 4 +/IgG+ was high in Kimura9s disease, but not in cutaneous pseudolymphoma. Conclusions The solitary skin lesions of IgG 4 -related disease were similar histologically and immunohistochemically to the skin lesions of Kimura9s disease. The concept of IgG 4 -related disease may help clarify the pathomechanism of diseases of unknown aetiology that possess features of IgG 4 -related disease.