Case report: VEXAS syndrome: an atypical indolent presentation as sacroiliitis with molecular response to azacitidine.

VEXAS syndrome is a recently described autoinflammatory syndrome caused by the somatic acquisition of mutations in myeloid precursors and is frequently associated with hematologic malignancies, chiefly myelodysplastic syndromes. Disease presentation can mimic several rheumatologic disorders, delaying the diagnosis. We describe a case of atypical presentation resembling late-onset axial spondylarthritis, later progressing to a systemic inflammatory syndrome with chondritis, cutaneous vasculitis, and transfusion-dependent anemia, requiring high doses of steroids. Ruxolitinib was used as the first steroid-sparing strategy without response. However, azacitidine showed activity in controlling both inflammation and the mutant clone. This case raises the question of whether azacitidine's anti-inflammatory effects are dependent on or independent of clonal control. We discuss the potential relevance of molecular remission in VEXAS syndrome and highlight the importance of a multidisciplinary team for the care of such complex patients.