Revisiting the impact of immunoglobulin isotypes in multiple myeloma

Changes in RDW according to prognostic predictors in newly diagnosed multiple myeloma

RDW is an erythrocyte index that increase in multiple myeloma, in which it appears to have an important role in predicting outcome. For this reason, we performed a retrospective analysis to evaluate the relationships of RDW with some important prognostic predictors. Specifically, in a cohort of 190 newly diagnosed multiple myeloma patients, we have examined the behaviour of RDW and its trend in relation to the ISS stage and other prognostic factors, such as albumin, beta-2 microglobulin, LDH and bone marrow plasma cell infiltration. We performed the analysis in the entire cohort of patients and in the three different disease isotypes (Light chain, IgA, and IgG multiple myeloma). The evaluation of RDW in the different isotypes was made with the Kruskal-Wallis test, integrated by the Dunn test. The comparison between the subgroups allocated above and below the median value of each prognostic factor, was made with the Mann-Whitney test. From our analysis, we observed that RDW is higher in the IgA multiple myeloma, and it increases significantly from ISS I to III. Moreover, RDW increases in the presence of lower albumin values, higher levels of beta2-microglobulin and LDH and in the presence of a greater bone marrow plasma cell infiltrate.

[Clinical characteristics and prognosis of newly diagnosed multiple myeloma patients with FGFR3 gene mutations]

Objective: This study aimed to investigate the influence of FGFR3 gene mutations on the clinical characteristics and prognosis of patients with newly diagnosed multiple myeloma (NDMM) . Methods: A total of 198 patients with NDMM admitted to the Department of Hematology in Jiangsu Province Hospital between January 2016 and February 2023 were retrospectively analyzed. Next-generation sequencing and cytoplasmic light chain immunofluorescence with fluorescence in situ hybridization were performed for all patients. The prognostic significance of FGFR3 mutation and clinical features were analyzed using the Log-rank test and Cox proportional hazards model. Results: Among 198 patients, 28 carried the FGFR3 gene mutation. These patients had significantly lower serum albumin levels, higher β(2)-microglobulin levels, advanced Revised International Staging System stages, more frequent occurrence of t (4;14) , and shorter median progression-free survival (PFS) time (28 months vs 33 months, P=0.024) and overall survival (OS) time (54 months vs undefined, P=0.028) than patients without FGFR3 mutation. Additionally, patients carrying either FGFR3 mutation or t (4;14) had lower PFS (30 months vs 38 months, P=0.012) and OS (54 months vs undefined, P=0.017) than those without. The Cox proportional hazards model identified FGFR3 mutation as an independent risk factor for PFS and OS. Conclusion: FGFR3 gene mutation was an unfavorable independent prognostic predictor for NDMM.

Differences in the immunoglobulin gene repertoires of IgG versus IgA multiple myeloma allude to distinct immunopathogenetic trajectories

The analysis of the immunogenetic background of multiple myeloma (MM) has proven key to understanding disease ontogeny. However, limited information is available regarding the immunoglobulin (IG) gene repertoire in MM cases carrying different heavy chain isotypes. Here, we studied the IG gene repertoire in a series of 523 MM patients, of whom 165 and 358 belonged to the IgA and IgG MM groups, respectively. IGHV3 subgroup genes predominated in both groups. However, at the individual gene level, significant (p<0.05) differences were identified regarding IGHV3-21 (frequent in IgG MM) and IGHV5-51 (frequent in IgA MM). Moreover, biased pairings were identified between certain IGHV genes and IGHD genes in IgA versus IgG MM. Turning to the imprints of somatic hypermutation (SHM), the bulk of rearrangements (IgA: 90.9%, IgG: 87.4%) were heavily mutated [exhibiting an IGHV germline identity (GI) <95%]. SHM topology analysis disclosed distinct patterns in IgA MM versus IgG MM cases expressing B cell receptor IG encoded by the same IGHV gene: the most pronounced examples concerned the IGHV3-23, IGHV3-30 and IGHV3-9 genes. Furthermore, differential SHM targeting was also identified between IgA MM versus IgG MM, particularly in cases utilizing certain IGHV genes, alluding to functional selection. Altogether, our detailed immunogenetic evaluation in the largest to-date series of IgA and IgG MM patients reveals certain distinct features in the IGH gene repertoires and SHM. These findings suggest distinct immune trajectories for IgA versus IgG MM, further underlining the role of external drive in the natural history of MM.