Vacuoles, E1 Enzyme, X-linked, Autoinflammatory, Somatic (VEXAS) Syndrome Mimicking Antineutrophil Cytoplasmic Antibody (ANCA)-Associated Vasculitis: A Delayed Diagnosis in a Patient With Multisystem Inflammation and Neutrophilic Dermatosis.

Vacuoles, E1 enzyme, X-linked, autoinflammatory, somatic (VEXAS) syndrome is a recently described adult-onset autoinflammatory disorder caused by somatic mutations in the UBA1 gene, characterized by systemic inflammation and hematologic abnormalities. Due to its broad and overlapping clinical manifestations, VEXAS is frequently misdiagnosed as other rheumatologic or hematologic conditions, leading to delays in diagnosis. We present the case of a 67-year-old man initially diagnosed with antineutrophil cytoplasmic antibody (ANCA)-associated vasculitis who developed progressive multisystem inflammatory disease, including migratory inflammatory arthritis, chondritis, scleritis, constitutional symptoms, and persistent macrocytic anemia. Despite treatment with corticosteroids and rituximab, his symptoms persisted. Bone marrow biopsy demonstrated cytoplasmic vacuolization in myeloid and erythroid precursors, and subsequent next-generation sequencing identified a somatic UBA1 mutation, confirming the diagnosis of VEXAS syndrome. His clinical course was further notable for the development of neutrophilic dermatosis consistent with Sweet's syndrome. This case highlights the diagnostic complexity of VEXAS syndrome and underscores the importance of recognizing characteristic clinical patterns, including macrocytic anemia, chondritis, and dermatologic manifestations, particularly in older male patients with refractory inflammatory disease. Early consideration of VEXAS and timely molecular testing may reduce diagnostic delay and facilitate more targeted management of this emerging hematoinflammatory disorder.