VEXAS syndrome in a patient with seropositive rheumatoid arthritis: lessons in diagnostic vigilance.

VEXAS syndrome (vacuoles, E1 enzyme, X-linked, autoinflammatory and somatic) is a recently recognised, adult-onset autoinflammatory condition caused by somatic UBA1 mutations, predominantly affecting older men. This condition often mimics autoimmune or infectious diseases, presenting with systemic inflammation and haematologic abnormalities. We describe a man in his 70s with seropositive rheumatoid arthritis who presented with a tender neck mass, recurrent fevers and elevated inflammatory markers. Symptoms improved with corticosteroids but relapsed on tapering. A bone marrow biopsy to investigate persistent inflammation revealed subtle cytoplasmic vacuolation in myeloid precursors, prompting targeted genetic testing that confirmed a somatic UBA1 mutation. This case underscores the diagnostic complexity of VEXAS and the therapeutic challenges of managing this recently recognised entity.