A high-throughput amplicon screen for somatic UBA1 variants in Cytopenic and Giant Cell Arteritis cohorts
AbstractSomatic mutations in the gene encoding the major E1 ubiquitin ligase, UBA1, were recently identified as a cause of VEXAS, a late-onset acquired auto-inflammatory syndrome. Differential diagnoses for patients subsequently found to have VEXAS include relapsing polychondritis, Sweet’s syndrome, myelodysplastic syndrome (MDS), giant cell arteritis (GCA) and undifferentiated systemic autoinflammatory disease (uSAID). We therefore sought to screen DNA from individuals with a non-diagnostic cytopenia or GCA, for known VEXAS-associated mutations. To this end, we developed a multiplexed UBA1 amplicon sequencing assay, allowing quick screening of large cohorts while also providing sufficient sequencing depth to identify somatic mutations to an allele frequency <1%. Using this assay, we screened genomic DNA from 612 males diagnosed with GCA, and bone marrow DNA from 1,055 cases with an undiagnosed cytopenia. No GCA cases were found to have UBA1 mutations, however 4 different mutations in the cytopenic cohort were identified in 7 individuals. Furthermore, we describe a female case identified in the screen with a UBA1 mutation and all VEXAS-associated phenotypes, but without Monosomy X. Our study suggests that, despite the overlap in clinical features, VEXAS is rarely misdiagnosed as GCA, but identified in 1.0% of males with an undiagnosed cytopenia. The identification of a UBA1 variant in a female case adds further evidence that VEXAS should not be ruled out as a differential diagnosis in females with VEXAS-like symptoms.Key points-Mutations in UBA1 exon 3 have been associated with VEXAS syndrome-UBA1 exon 3 was screened in 1650 patients with cytopenia or GCA by amplicon sequencing.-6 males were identified from the non-diagnostic cytopenia cohort (1.0%) with UBA1 mutations.-A female with a somatic UBA1 mutation was identified without Monosomy X
