Recurrent Epistaxis as a Rare Presentation of Extramedullary Multiple Myeloma.

Extramedullary multiple myeloma is characterized by clonal plasma cell proliferation outside the bone marrow and is associated with an adverse prognosis, particularly when accompanied by high-risk cytogenetic abnormalities. Sinonasal involvement is rare and may present with recurrent epistaxis or unilateral nasal obstruction, creating diagnostic overlap with inflammatory, vascular, lymphoid, and epithelial sinonasal lesions. We report a 54-year-old man with an eight-month history of progressive right-sided nasal obstruction and intermittent epistaxis that became increasingly frequent and refractory to nasal packing. Magnetic resonance imaging showed a right sinonasal mass involving the nasal cavity and maxillary sinus, with septal deviation and no radiological evidence of orbital floor or nasal septal erosion. Endoscopically guided biopsy demonstrated a dense plasma cell infiltrate with mature and atypical forms. Systemic evaluation revealed anemia, multiple lytic skull and humeral lesions, 32% bone marrow plasma cell infiltration, an IgG monoclonal protein with lambda light-chain restriction, and high-risk cytogenetic abnormalities including CKS1B 1q gain, deletion 17p, and deletion 13q. These findings established a diagnosis of high-risk symptomatic multiple myeloma with extramedullary sinonasal involvement rather than a solitary extramedullary plasmacytoma. This case emphasizes that recurrent epistaxis associated with a unilateral sinonasal mass warrants early biopsy and systemic evaluation, particularly when clinical or laboratory features suggest an underlying plasma cell neoplasm.