Spleen Involvement at Diagnosis of Multiple Myeloma: A Case Report and Literature Review

Multiple myeloma (MM) is more often characterized by clonal plasma cell proliferation restricted to the bone marrow. However, a small percentage of patients with MM develop extramedullary disease (EMD): this type of localization is found in 1.7%-4.5% of the newly diagnosed MM (ND/MM) and in 3.4%-10% of patients with relapsed or refractory disease (RR/MM) and seems to have a bad prognostic impact. In the present report, we describe a very rare case of splenic involvement in a patient with ND/MM.

A 72-year-old female was referred to Santa Rosa Hospital of Viterbo in June 2022 with asthenia and abdominal pain. At physical examination, spleen enlargement was detected, with anemia (Hb 10.5 g/dL) and thrombocytopenia (48 × 10⁹/L). Abdominal echography confirmed spleen enlargement (20 cm of longitudinal diameter). Blood tests showed free light chain alteration with a λ/κ ratio of 800. Marrow aspiration showed 60% of λ-restricted immature plasma cells: p53 expression was present in 91% of elements. Positron emission tomography/computed tomography (PET/CT) scan revealed multiple focal areas of increased metabolic activity in the bones and a widespread positivity of the spleen with focal areas of higher uptake. A diagnosis of MM with splenic EMD was made, and the Dara-VMP regimen (daratumumab, bortezomib, melphalan, and prednisone) was started. After the first cycle of therapy, a marked reduction in spleen size was observed with an increase in both Hb level and platelet count. After the second cycle of therapy, however, there was evolution into plasma cell leukemia: the Vd-PACE regimen (bortezomib, dexamethasone, cisplatin, doxorubicin, cyclophosphamide, and etoposide) was thus started, but after the second cycle, she died in October 2022 from septic shock and multiorgan failure.

Our very rare case of ND/MM with spleen involvement confirms the aggressive behaviour of EMD, with negative prognostic factors (p53 mutation) and failure to frontline highly effective therapy. In the other few cases of spleen involvement reported, however, there were only scarce details about response: as a consequence, collection of similar cases is warranted to fully understand clinical features and possible alternative approaches for these extremely rare patients.