Multiple Myeloma in Children and Young Adults: A Systematic Literature Review

Multiple myeloma (MM) is extremely rare in pediatric and young adult populations, and its clinical characteristics, therapeutic strategies, and outcomes remain poorly defined. This systematic review consolidates all published cases of MM in patients aged ≤ 25 years, aiming to define epidemiology, presentation, treatment, and theraupeutic outcomes. A systematic literature search was conducted in PubMed up to December 31, 2024, to identify case reports and series of MM in patients ≤ 25 years. Articles lacking patient-specific data, definitive diagnostic criteria, or full English text were excluded. Data on demographics, clinical features, cytogenetics, treatment regimens, and outcomes were extracted. Forty-two patients were included from 33 publications, with a median age of 17 years (range 8-25). Male predominance was noted (M: F = 1.47:1). Common presenting features included bone pain (42.9%) and neurological symptoms (21.4%). IgG myeloma was most frequent, followed by IgA, light-chain only and IgD subtypes. Plasmacytomas were observed in 61.9%, including 30.8% with extramedullary and 57.7% with paramedullary involvement. Cytogenetic abnormalities were detected in 75% of evaluable patients. First-line therapy varied by era, with regimens including conventional chemotherapy, novel agents, and hematopoietic stem cell transplantation (HSCT). Among the 16 patients with evaluable treatment response, the overall response rate to first-line therapy was 75%. Hematopoietic stem cell transplantation (HSCT) was performed in 10 patients and was associated with deeper treatment responses. Contemporary therapeutic regimens were generally well tolerated, and no therapy-related mortality was reported. MM in patients aged ≤ 25 years is a rare clinical entity that may present with distinctive features, including a high frequency of plasmacytomas and extramedullary disease. Modern treatment strategies incorporating novel agents and HSCT appear feasible and effective in this population. Further collaborative studies are required to better define the biological characteristics and optimal management of MM in very young patients.