ABSTRACT
Introduction: Multiple myeloma (MM) is a hematological malignancy of plasma cells. The diagnosis is confirmed by the presence of clonal plasma cells in the bone marrow. Cytological examination of cells in bone marrow smear is used to determine atypical plasma cell morphology but flow cytometry immunophenotyping (FCI) is a method used to determine the clonality and aberration of plasma cell immunophenotype. Both characteristics of plasma cell immunophenotype should be determined at the time of diagnosis, but also during the therapy follow-up, to ensure that the same clone is present. Most patients with MM display immunosuppression related to the disease and the therapies. Common complications include serious infections. The SARS-CoV-2 viral infection in patients with MM may have a more aggressive course and cause higher mortality. Here, we presented the patient with MM in remission that relapsed after coronavirus disease 2019 (COVID-19). Method(s): 73 - year-old man with MM in remission was admitted to the Department of Clinical Hematology of the University Hospital Osijek due to weakness, significantly elevated inflammation markers (CRP and IL-6) and positive RT-PCR test for SARS-CoV-2 virus. Prior to this infection, the patient achieved remission of MM. It was confirmed by cytomorphological and FCI analysis of bone marrow aspirate three months ago, but a new performance of these analysis has now been requested. Result(s): Cytomorphological analysis found the presence of 50% abnormal plasma cells in bone marrow aspirate FCI analysis showed that plasma cells express surface markers CD38+CD138+CD56++CD117+ and cytoplasmic immunoglobulin light chain lambda This abberant immunophenotype corresponded to the original clone of plasma cells found at diagnosis Conclusion(s): Results showed that acute SARS-CoV-2 infection could accelerate the course of hematological disorders involving plasma cells, even after remission was achieved. Future studies of this topic should include the mechanisms involved in relapse of MM after viral infection. One of possible causes is the production of IL- 6, the most abundant cytokine in the plasma of patients with COVID-19. IL-6 modulates B-cell differentiation which can lead to the progressive reactivation of lymphoid and plasma cell malignances.