UBA1 and VEXAS syndrome: Somatic mutations in UBA1 that cause VEXAS are located at the methionine 41 (M41) residue or close to it and abrogate the expression of the short isoform of UBA1 (UBA1b), which starts with M41 and is localized in the cytoplasm, in contrast to its longer counterpart (UBA1a) which mainly displays a nuclear localization.53