Characteristics of 15 Subjects Affected by IgD Multiple Myeloma and the Key Role of the Laboratory in Diagnosis: A Retrospective Study Report and Literature Review

Immunoglobulin D (IgD) myeloma represents an uncommon subtype of multiple myeloma (MM), accounting for 1–2% of cases. Subjects affected by IgD MM have been demonstrated to have an inferior outcome and survival compared to those with other MM subtypes. A retrospective study was conducted on 15 patients (9 males and 6 females) diagnosed from 2008 to 2022 with IgD MM, in order to investigate the clinical and biochemical features at the moment of diagnosis, cytogenetic alterations, and survival times. The median age was 69 years, and higher frequencies of bone lesions, renal impairments, Bence–Jones proteinuria, and increased serum LDH were observed. Serum calcium levels were in the reference ranges. In the assessment of protein electrophoresis patterns, nine patients had a serum monoclonal protein that was not detectable. A cytogenetic analysis via fluorescence in situ demonstrated that the most common abnormalities were the deletion of 13q and IGH rearrangements. Patients treated with new chemotherapeutic drugs (immunomodulators, proteasome inhibitors), with or without autologous stem cell transplantation presented a higher median survival. The fundamental role of the laboratory in monoclonal IgD detection and the monitoring and studying of IgD MM cases enhances the knowledge of this disease, thus improving patient outcomes.