Genomic ascertainment for UBA1 variants and VEXAS syndrome: a population-based study

Importance VEXAS (vacuoles, E1-ubiquitin-activating enzyme, X-linked, autoinflammatory, somatic) syndrome is a disease with rheumatologic and hematologic features caused by somatic variants in UBA1 . Pathogenic variants are associated with a broad spectrum of clinical manifestations. Knowledge of prevalence, penetrance, and clinical characteristics of this disease have been limited by ascertainment biases based on known phenotypes. This study used a genomic ascertainment approach to overcome these limitations and better define UBA1 -related disease. Objective Determine the prevalence of pathogenic variants in UBA1 and associated clinical manifestations in an unselected population using a genomic ascertainment approach. Design, Setting and Participants This cohort study evaluated UBA1 variants in exome data from 163,096 participants within the Geisinger MyCode Community Health Initiative. Clinical phenotypes were determined from Geisinger electronic health record (EHR) data up to January 1st, 2022. Main outcomes and measures Prevalence of somatic UBA1 variation; presence of rheumatologic, hematologic, pulmonary, dermatologic, and other symptoms in individuals with somatic UBA1 variation; structured and manual review of EHR; review of bone marrow biopsies; survival in carriers of somatic UBA1 variation. Results In a retrospective study of 163,096 participants (mean age 52.8 years; 94% of European ancestry, 61% female), 11 individuals harbored somatic, known pathogenic UBA1 variants, with 100% having clinical manifestations consistent with VEXAS syndrome. We found a previously unreported UBA1 variant (c.1861A>T; p.Ser621Cys) in a symptomatic patient. Disease-causing UBA1 variants were found in ∼1 in 14,000 unrelated individuals, and ∼1 in 4,000 men >50 years old. A disease-causing UBA1 variant confers a ∼ 6.6 higher probability of mortality vs. age-, sex-, and BMI-matched non-carriers. The majority (7, 58%) of individuals did not meet criteria for rheumatologic and hematologic diagnoses previously associated with VEXAS syndrome, however all individuals had anemia (mean 7.8 g/dL, median 7.5g/dL), mostly macrocytic (91%) with concomitant thrombocytopenia (91%). Finally, we identified a pathogenic variant in one male prior to onset of VEXAS-related signs or symptoms and two females had disease with heterozygous variants. Conclusions and relevance This cohort study showed that the prevalence, penetrance, and expressivity of pathogenic UBA1 variants were higher than expected. More expansive UBA1 testing will lead to molecular diagnoses and improved treatment for patients. ### Competing Interest Statement The authors have declared no competing interest. ### Funding Statement This research was supported by Intramural Research Program of the Division of Cancer Epidemiology and Genetics of the National Cancer Institute and of the National Institutes of Health. D.B.B. was supported by the Relapsing Polychondritis Foundation and funding from the NIH (R00AR078205). ### Author Declarations I confirm all relevant ethical guidelines have been followed, and any necessary IRB and/or ethics committee approvals have been obtained. Yes The details of the IRB/oversight body that provided approval or exemption for the research described are given below: Institutional review board (IRB) of Geisinger Medical Center gave ethical approval for this work. I confirm that all necessary patient/participant consent has been obtained and the appropriate institutional forms have been archived, and that any patient/participant/sample identifiers included were not known to anyone (e.g., hospital staff, patients or participants themselves) outside the research group so cannot be used to identify individuals. Yes I understand that all clinical trials and any other prospective interventional studies must be registered with an ICMJE-approved registry, such as ClinicalTrials.gov. I confirm that any such study reported in the manuscript has been registered and the trial registration ID is provided (note: if posting a prospective study registered retrospectively, please provide a statement in the trial ID field explaining why the study was not registered in advance). Yes I have followed all appropriate research reporting guidelines and uploaded the relevant EQUATOR Network research reporting checklist(s) and other pertinent material as supplementary files, if applicable. Yes All data produced in the present study are available upon reasonable request to the authors