Pathogenic <i>UBA1</i> variants associated with VEXAS syndrome in Japanese patients with relapsing polychondritis.

Abstract

To determine clinical and genetic features of individuals with relapsing polychondritis (RP) likely caused by pathogenic somatic variants in ubiquitin-like modifier activating enzyme 1 (<i>UBA1</i>). Fourteen patients with RP who met the Damiani and Levine criteria were recruited (12 men, 2 women; median onset age (IQR) 72.1 years (67.1-78.0)). Sanger sequencing of <i>UBA1</i> was performed using genomic DNA from peripheral blood leukocytes or bone marrow tissue. Droplet digital PCR (ddPCR) and peptide nucleic acid (PNA)-clamping PCR were used to detect low-prevalence somatic variants. Clinical features of the patients were investigated retrospectively. <i>UBA1</i> was examined in 13 of the 14 patients; 73% (8/11) of the male patients had somatic <i>UBA1</i> variants (c.121A>C, c.121A>G or c.122T>C resulting in p.Met41Leu, p.Met41Val or p.Met41Thr, respectively). All the variant-positive patients had systemic symptoms, including a significantly high prevalence of skin lesions. ddPCR detected low prevalence (0.14%) of somatic variant (c.121A>C) in one female patient, which was subsequently confirmed by PNA-clamping PCR. Genetic screening for pathogenic <i>UBA1</i> variants should be considered in patients with RP, especially male patients with skin lesions. The somatic variant in <i>UBA1</i> in the female patient is the first to be reported.