IgG4-related skin lesions: case report and review of the literature.

IgG4-related disease (IgG4-RD) is a systemic disease, mostly affecting the pancreas. It presents as accumulation of IgG4-producing plasma cells in various tissues. Other possible affected organs include the lacrimal glands, salivary glands, lungs, kidneys, liver, bile duct, retroperitoneum, breast, aorta, pituitary gland and prostate. A cutaneous presentation has also been described in the literature, and might be the initial presenting feature of IgG4-RD. We describe a 73-year-old white man who presented with two infiltrated, erythematous nodules on his abdomen. The histopathological characteristics were highly suggestive of IgG4-related cutaneous disease. Immunohistochemical stains were positive for IgG4. In the past, the patient's other organs had also been affected by IgG4-RD. Cutaneous presentation of IgG4-RD has been described previously in the literature but only in Asian patients (both East and South Asian). We also provide an overview of previously reported cutaneous manifestations of IgG4-RD.