Lambda Light Chain Plasmacytoma Presenting with Paraneoplastic Leukocytoclastic Vasculitis in the Context of Septic Shock: A Case Report

Introduction:Leukocytoclastic vasculitis (LCV) is a small-vessel vasculitis characterized by immune complex deposition presenting with palpable purpura and petechiae. While commonly associated with systemic conditions such as infections and autoimmune diseases, LCV can be triggered less commonly by hematologic malignancies. Plasma cell disorders may lead to LCV through immune dysregulation and abnormal immunoglobulin production.1 The association between plasma cell dyscrasias and LCV emphasizes the importance of thorough evaluation in patients presenting with vasculitis, specifically those with underlying immunologic conditions. Case:A 60-year-old man with a history of monoclonal gammopathy of undetermined significance (MGUS) and systemic lupus erythematosus (SLE) with cutaneous features presented with petechiae, weight loss, and sixth months of constitutional symptoms. A punch biopsy confirmed LCV. Imaging revealed mesenteric and paraspinal nodules, and biopsy identified plasmacytoma. Laboratory evaluation showed elevated immunoglobulins (IgG 6000 mg/dL, IgA 2000 mg/dL) and markers of immune dysregulation. The patient’s course was complicated by septic shock, necessitating intensive care. Despite this, he stabilized and initiated dermatology-directed treatment for cutaneous lesions. Subsequent autologous hematopoietic stem cell transplantation and chemotherapy led to improvement in both systemic and cutaneous disease. Conclusion:This case highlights LCV as a paraneoplastic syndrome and a potential harbinger of plasma cell malignancy. Notably, resolution of LCV was achieved following definitive treatment of the underlying malignancy, emphasizing the importance of systemic therapy. Recognition of LCV as a manifestation of hematologic malignancy necessitates thorough evaluation, particularly in patients with pre-existing plasma cell disorders.