MGUS prevalence among active-duty military personnel

Monoclonal gammopathy of undetermined significance (MGUS) is a precursor condition for multiple myeloma, and although environmental exposures have been implicated in its pathogenesis, it is unknown whether exposure to open-air burn pits used during U.S. military operations in Iraq affects prevalence of MGUS in active-duty service members (ADSMs). ADSMs represent a distinct young and physically fit population, with higher proportions of male and Black individuals compared to the general U.S. population. This retrospective cohort study evaluated MGUS prevalence among ADSMs. Participants included ADSMs deployed to Iraq with self-reported burn pit exposure (DEP-IQ; n = 534), ADSMs deployed to Germany without burn pit exposure (DEP-DEU; n = 534), and non-deployed ADSMs (NON-DEP; n = 521). Eligibility criteria included deployment ≥180 days, age ≥35 years at deployment, and ≥10 years of continued military service. Serum samples collected 11-14 years post-deployment were analyzed using serum protein electrophoresis, immunofixation, and serum free light chain (sFLC) assays. MGUS and light-chain MGUS (LC-MGUS) prevalence were estimated using conventional and revised age-stratified sFLC reference intervals. MGUS + revised LC-MGUS prevalence did not differ between DEP-IQ (5.6%), DEP-DEU (4.3%), and NON-DEP (5.2%) cohorts. The overall total prevalence of MGUS + revised LC-MGUS was 5% and was higher in Black (10.4%) than White ADSMs (3.9%), p < 0.001. When using conventional sFLC reference intervals, LC-MGUS was more frequently identified among deployed ADSMs (1.6%) compared with non-deployed ADSMs (0.2%); however, this association was no longer significant when revised reference intervals were applied. These findings suggest that military service may involve cumulative or non-burn pit exposures contributing to plasma cell dysregulation. Application of updated sFLC reference ranges is critical to avoid overestimation of LC-MGUS. Long-term studies are warranted to define progression risk and inform targeted screening strategies in ADSMs.