Extramedullary dissemination in multiple myeloma: a case report of rare leptomeningeal involvement and comprehensive treatment outcomes.

Multiple myeloma (MM) is a clonal plasma cell malignancy often confined to the bone marrow, although extramedullary disease (EMD) can develop, especially in advanced or relapsed cases. Leptomeningeal EMD is a rare and aggressive manifestation associated with a dismal prognosis. This case report highlights the critical role of 18F-FDG PET/CT in managing such complex presentations.