Relapse of Mutiple Myeloma after Autologous Stem Cell Transplant Presenting with Central Nervous System Involvement without Evidence of Bone Marrow Involvement: The First Report of a Rare Clinical Entity

Multiple myeloma (MM) is characterized by uncontrolled clonal proliferation of plasma cells, mainly in bone marrow, and Extramedullary involvement is rare in MM. The incidence of extramedullary plasmacytomas is 7% to 18% at MM diagnosis and up to 20% at relapse.¹ The presence of extramedullary involvement in MM represents aggressive disease, and is associated with shorter overall and progression-free survival.² Extramedullary involvement commonly the nasopharyngeal, larynx, skin, upper respiratory tract, and central nervous system (CNS). The involvement of the CNS by MM, as defined by the presence of plasma cells in the cerebrospinal fluid (CSF) in a patient with MM, is considered extremely rare and is estimated only in 1% of patients. The best treatment regimen for MM with CNS involvement is still unknown and in most patients, the prognosis is unfavorable.⁴ To date, there is no report of CNS involvement without evidence of systemic involvement in a known case with MM. To the best of our knowledge, this is the first published report of CNS involvement without evidence of systemic involvement in a known patient with MM relapse following autologous stem cell transplant.