Decoding duality: Unraveling biclonal myeloma through flow cytometry and cytogenetics

This report details the case of a 62-year-old female diagnosed with biclonal multiple myeloma (MM), a rare plasma cell proliferative disorder characterized by the simultaneous production of two distinct monoclonal proteins. The patient presented with non-specific symptoms, and initial laboratory and imaging findings were suggestive of typical MM. While serum free light chain assays indicated potential biclonality, traditional serum protein electrophoresis and immunofixation electrophoresis failed to definitively identify two distinct monoclonal light chains. The definitive diagnosis was achieved through multiparametric flow cytometry (MFC), which precisely identified two distinct plasma cell populations with differing light chain restrictions. Further genetic analysis through fluorescent in situ hybridization revealed high-risk cytogenetic abnormalities, including deletion 13q14.2 (RB1/deleted in leukemia (gene locus) [DELU]) and gain of 1q21.22 cyclin-dependent kinase regulatory subunit 1B (CKS1B), alongside hypodiploidy, all correlating with a poor prognosis and potential drug resistance. This case underscores the critical role of advanced diagnostic techniques, particularly MFC, in identifying rare and complex plasma cell dyscrasias and highlights the prognostic significance of co-occurring genetic aberrations in guiding management strategies for this challenging condition.