Multiorgan Serum IgG4-related Disease Diagnosed with Dermatopathology: A Case Report

Immunoglobulin G4-related disease (IgG4-RD) is a recently discovered condition that was first reported in 2001. It is characterized by IgG4-positive plasma cell infiltration. Cutaneous involvement is rare but increasingly reported. A 48-year-old male presented with multiple, black-brown, indurated plaques on his trunk and axillae. Laboratory examination revealed anemia of unknown etiology and hyperglobulinemia with markedly elevated serum IgG and IgG4 levels. Histopathologic examination showed lymphoplasmacytic infiltration with abundant IgG4-positive plasma cells. The bone marrow biopsy results were consistent with the skin biopsy. Computed tomography demonstrated multiple lymph node involvement. Under the care of the rheumatology department, the patient has been treated with a systemic steroid and immunosuppressive agents, and he has shown gradual improvement in the laboratory findings.