Abstract

IgG4 related disease is an uncommon disorder with a prevalence of 64 per million. It is an immune-mediated, fibroinflammatory condition that affects multiple organs and clinically, presents as tumor-like enlargement of organs. Histologically, it is characterized by lymphoplasmacytic infiltrate with IgG4 positive plasma cells, storiform fibrosis, and obliterative phlebitis. The current criteria include: 1) swelling or masses, 2) serum IgG4 concentration >135 mg/dL, and 3) >40% of IgG+ plasma cells being IgG4+ and >10 cells/high power field of biopsy sample. Here we present a case of a 61-year old woman with a 4-year history of pruritic dermatitis involving her face, extremities, and back consisting of pink crusted grouped papules coalescing into confluent scaly plaques with no lymphadenopathy. She underwent numerous antibiotics and topical corticosteroid treatments which mildly improved her symptoms for the duration of the therapy but overall, her symptoms continued to worsen. The initial working differential included scabies and neurodermatitis in a patient with possible undiagnosed lymphoproliferative disorder. Biopsies demonstrated an epidermis with excoriation, acanthosis, and spongiosis. Within the superficial dermis, there was a mild to moderate perivascular mixed inflammatory infiltrate composed of lymphocytes, histocytes, a prominent number of eosinophils, and plasma cells. Scabies was not identified. Kappa and lambda light chain analysis by in-situ hybridization demonstrated a polyclonal population of plasma cells. Immunohistochemistry for IgG and IgG4 demonstrated a prominent increased number of IgG4 plasma cells (at least 50%). Laboratory markers for IgE (>15 000 IU/mL) and IgG4 (515 mg/dL) were elevated. While no one features is diagnostic, the histologic findings in conjunction with the serologic findings would support the uncommon diagnosis of IgG4 related disease involving the skin.

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