There was no association between autoimmune diseases and monoclonal gammopathy of undetermined significance (MGUS) in a large systematically screened population, according to a study published in Annals of Internal Medicine.1
Based on this finding, “routine screening for MGUS among individuals with autoimmune disease is not recommended,” said study researcher Ingigerdur Sverrisdottir, MD, of University of Iceland in Reykjavik and Sahlgrenska University Hospital in Gothenburg, Sweden.
Because previous studies have found an increased prevalence of MGUS in certain disease groups, such as systemic lupus erythematosus and rheumatoid arthritis, it is common practice to screen for MGUS among patients with autoimmune diseases, especially among rheumatologists and in internal medicine, Dr. Sverrisdottir explained.
However, these prior registry-based, retrospective studies were inclined to ascertainment bias.
In this analysis, Dr. Sverrisdottir and colleagues sought to examine if there was an association between autoimmune diseases and MGUS in a larger unselected population. They conducted a cross-sectional study within iStopMM (Iceland Screens, Treats, or Prevents Multiple Myeloma), a prospective, population-based screening study of MGUS.
The analysis included 75,422 Icelanders aged 40 years or older who had volunteered to participate in the iStopMM study. Of the 10,818 participants (14.5%) who had an autoimmune disorder, 599 (5.5%) had MGUS; this included 61 participants (0.6%) with a prior clinical diagnosis of MGUS and 538 (5.0%) who were diagnosed upon study screening.
There was no association between autoimmune diseases and MGUS. Participants with an autoimmune disease had the same likelihood of having MGUS as those without an autoimmune disease (prevalence ratio [PR] = 1.05; 95% CI 0.97-1.15). Additionally, there was no association between autoimmune disease and subtypes of MGUS.
Looking at 42 specific autoimmune diseases, only Guillain-Barré syndrome was associated with the primary outcome of MGUS; however, the researchers acknowledged that this was based only on four participants in the MGUS group.
There was a higher prevalence of prior clinical MGUS in participants with an autoimmune disease compared with no autoimmune disease (0.6% vs. 0.3%), indicating that autoimmune disease diagnoses were associated with a prior clinical diagnosis of MGUS (PR=1.64-2.70).
“As MGUS is an asymptomatic condition, not a disease, prior MGUS was usually found during the workup of various symptoms, such as anemia, joint, or back pain,” Dr. Sverrisdottir explained. “In addition to finding an M-protein without any evidence of a malignancy, many of these individuals were then diagnosed with an autoimmune condition. However, when the population in our study was screened for MGUS, no relationship was found.”
The study was limited by the use of registry data to gather information on autoimmune diseases and by the homogeneity of the Icelandic population. However, Dr. Sverrisdottir said these findings should be generalizable to populations outside of Iceland.
“Even though the Icelandic population is mostly of Northern European descent, the screened design [of this study] gives the most correct prevalence of MGUS to date,” Dr. Sverrisdottir said. “Over 50% of the target population did consent to participate, with even distribution between the sexes and rural/urban areas.”
In addition, Dr. Sverrisdottir said this finding is consistent with the only other prior screening study from Mayo Clinic,2 which had a smaller participant cohort and did not include light-chain MGUS cases.
Any conflicts of interest declared by the authors can be found in the original article.
References
- Sverrisdottir I, Thorsteinsdottir S, Rognvaldsson S, et al. Association between autoimmune diseases and monoclonal gammopathy of undetermined significance: an analysis from a population-based screening study. Ann Intern Med. 2024;177(6):711-718.
- Bida JP, Kyle RA, Therneau TM, et al. Disease associations with monoclonal gammopathy of undetermined significance: a population-based study of 17,398 patients. Mayo Clin Proc. 2009;84(8):685-693.
