Describing IgA Myeloma: An Immunophenotypic and Molecular Approach

Plasma cell myeloma (PCM) is defined as a clonal disease of terminally differentiated plasma cells that secrete immunoglobulin. The biologic underpinnings of IgA-type multiple myeloma's (IgAMM) aggressive nature, including its increased morbidity and mortality, have not been elucidated. We describe the clinical, phenotypic, and cytogenetic characteristics of IgA-MM. Flow-cytometry analysis was performed to phenotype clonal plasma cell populations, and interface with fluorescent in situ hybridization (iFISH) to exploit cytogenetics to determine risk stratification; 68.1% of cases were of intermediate or high risk. On flow cytometry, samples from our IgA-PCM cohort revealed less frequent CD56 expression when compared to samples with other PCM subtypes. Our study demonstrated lower frequency of CD56 expression (52.8%). We hypothesize that loss of CD56 may play a significant role in the aggressive behavior of IgA-PCM due to the loss of cell-to-cell adhesion resulting in a higher propensity for extramedullary presentation.