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Case Reports

Abstract

Castleman disease (CD) is a rare and poorly understood lymphoproliferative disorder, typically presenting with lymphadenopathy and systemic symptoms. Cutaneous involvement is uncommon. We report a case of idiopathic multicentric Castleman disease (iMCD) with skin findings in a 44-year-old male with a history of a left knee gunshot wound complicated by deep vein thrombosis. He presented with a two-month history of malaise, fevers, dyspnea, abdominal pain, and a 10-pound weight loss. PET/CT revealed FDG-avid lymphadenopathy in the axillary, retroperitoneal, iliac, pelvic, and inguinal regions, along with splenomegaly. Laboratory studies showed elevated ferritin, CRP, ESR, IgG, and microcytic anemia (hemoglobin 5.4). Interleukin-6 was elevated to 285 pg/mL. Lymph node biopsy confirmed iMCD. Dermatology was consulted for violaceous nodules on the trunk, present for one year. Skin biopsy showed variably dense superficial and deep perivascular and periadnexal infiltrates of mature plasma cells and small lymphocytes, with a well-formed lymphoid follicle and increased small-caliber vascular channels. Immunohistochemistry revealed a mixed population of CD3+ T cells and CD20+ B cells, with a kappa to lambda ratio of 2:1. HHV8 and EBV were negative. Findings were consistent with iMCD involving the skin. He was treated with siltuximab, leading to significant improvement in lymphadenopathy, ferritin levels, and skin lesions. His course was complicated by autoimmune hemolytic anemia, requiring robotic splenectomy, which showed no evidence of CD. This case highlights a rare cutaneous manifestation of iMCD, with polyclonal plasma cell and lymphoid infiltrates, lymphoid follicles, and vascular proliferation, preceding systemic symptoms by several months.