Posted: Thursday, October 30, 2025
A recent population-based cohort study found that patients with smoldering multiple myeloma (SMM) had a significantly higher infection risk than other populations. Individuals with SMM also had more antibacterial prescriptions, according to the Icelandic iStopMM study.
Lærke Sloth Andersen, MD, of the Department of Hematology, Rigshospitalet, Copenhagen, Denmark, and colleagues screened 75,422 Icelandic patients aged 40 years or older, to identify those with either SMM or monoclonal gammopathy of undetermined significance (MGUS). Individuals with SMM and MGUS were matched 1:1, and patients with SMM were matched 1:5 to those who were MGUS-free. Individuals were followed from date of SMM or MGUS diagnosis between 2016 and 2020, to May 1, 2022.
In time to first infection analyses over follow-up, those with SMM had a 36% higher hazard of any infection compared to those who were MGUS-free (HR 1.36, 95% CI 1.07–1.73) and a 37% increased risk relative to those with MGUS (HR 1.37, 95% CI 1.00–1.87). The SMM cohort's antibacterial prescription rates was also higher (HR 1.24, 95% CI 1.01–1.52). When adjusted for suppression of at least one uninvolved immunoglobulin, the HR dropped to 1.26 (95% CI 0.98–1.63). The study authors suggested that immunoparesis may mediate heightened infection susceptibility.
“Taken together, this suggests that even a modest disease burden, such as having ≥10% bone marrow plasma cells, may confer an impaired immune function or other biological vulnerabilities contributing to an increased susceptibility to infections,” Dr. Andersen said.
The study’s findings demonstrate how even in the absence of CRAB (calcium elevation, renal insufficiency, anemia, bone lesions) criteria or overt disease, asymptomatic plasma cell expansion may reflect immune system vulnerability. The study authors cautioned clinicians to be vigilant for infections in SMM, and suggested further research into whether SMM patients with recurrent infections have a higher progression risk to symptomatic multiple myeloma and whether targeted prophylaxis can alter this trajectory.
Disclosures: For full disclosures of study authors, visit nature.com.
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