Nodules behind the ears: IgG4-related skin disease

A 53-year-old healthy factory worker consulted our hospital complaining of small nodules of similar size, shape and location on both ears. The nodules revealed focal and massive infiltration of lymphocytes, plasma cells and eosinophils with fibrosis. They had no specific structure on pathological staining with haematoxylin and eosin. Immunostaining for IgG4 revealed that a large majority of the IgG⁺ cells were positive for IgG4. The ratio of IgG4⁺ to IgG⁺ plasma cells was approximately 40%. IgG4⁺ plasma cells were present at approximately 250 per high-power field. The patient was diagnosed with IgG4-related skin disease without multiple organ involvement in the systemic syndrome of IgG4-related diseases. Because the patient was a factory worker and exposed to an environment of metallic dust, a skin patch test that included a metal series was performed. Zinc and manganese produced positive reactions. Because only skin lesions were observed in this case, not multiple organ involvement, tissue infiltration by IgG4⁺ plasma cells might have resulted from continuous sensitization to zinc and/or manganese.