Aims The cutaneous manifestation of IgG4-related disease has rarely been reported. The aim of this study is to identify and describe the cutaneous manifestations associated with IgG4-positive plasma cell infiltration in the skin.
Methods The authors investigated two cases of IgG4-related disease with solitary skin lesions and compared the immunohistochemical characteristics of infiltrating cells among IgG4-related disease, Kimura's disease and cutaneous pseudolymphoma.
Results IgG4-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 IgG4-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-IgG4 antibodies, and the ratio of IgG4+/IgG+ cells was more than 50%. Serum levels of IgG and IgG4 were not elevated and no lesions were found in other organs. Skin samples taken from Kimura's disease showed histopathological features similar to those of IgG4-related disease. The proportion of IgG4+/IgG+ was high in Kimura's disease, but not in cutaneous pseudolymphoma.
Conclusions The solitary skin lesions of IgG4-related disease were similar histologically and immunohistochemically to the skin lesions of Kimura's disease. The concept of IgG4-related disease may help clarify the pathomechanism of diseases of unknown aetiology that possess features of IgG4-related disease.
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Competing interests None.
Patient consent Obtained.
Ethics approval Ethics approval was provided by the local ethics committee of Gunma University Hospital.
Provenance and peer review Not commissioned; externally peer reviewed.