Background/Purpose: VEXAS syndrome (vacuoles, E1 enzyme, X-linked, autoinflammatory, somatic) is anautoinflammatory syndrome caused by somatic mosaicism in the UBA1 gene. [¹⁸F]-FDG-PET/CT is often performed during the diagnostic workup of patients with VEXAS syndrome, but the abnormalities that may be detected with this imaging examination are not well described.

Methods: We performed a retrospective multicenter study in France and Belgium. Patients with confirmed VEXAS syndrome, defined by the presence of an autoinflammatory syndrome and detection of a pathogenic UBA1mutation, who underwent at least one [¹⁸F]-FDG-PET/CT were considered eligible. Data on the clinical presentation, laboratory results, genetic analyses, and [¹⁸F]-FDG-PET/CT imaging results were collected using a standardized form. In an exploratory analysis, the observed abnormalities were compared according to the clinical disease activity status and the VEXAS syndrome clusters as previously defined by Georgin-Lavialle et al. (Br J Dermatol 2022;186:564–74).

Results: A total of 106 [¹⁸F]-FDG-PET/CT scans were performed in 57 VEXAS patients. All patients were male and had a median age of 71 (IQR, 66-76) years at symptom onset and 75 (IQR 69-79) years at diagnosis. The most frequent clinical manifestations included cutaneous lesions (86%), fever (79%), arthralgia or arthritis (68%), pulmonary manifestations (46%), ear or nose chondritis (37%), and venous thrombo-embolism (33%). Only 29% of scans were performed before treatment for VEXAS, as the majority of patients received corticosteroids (66%) and/or other immunosuppressive treatments (40%) at the time of imaging. Patients most commonly had increased FDG uptake in the bone marrow (82%), lymph nodes (54%), lungs (37%), and spleen (30%). Less frequently, patients had hypermetabolism in the pleura (18%), nose or ear cartilage (9%), joints (5%), and pericardium (2%). Increased arterial FDG uptake was identified in 12% of patients, including aortic involvement (5%) and asymmetric artery involvement (9%). Significantly more abnormalities were detected by [¹⁸F]-FDG-PET/CT in VEXAS patients with active disease (median 3 [IQR 2-4]) compared to those in clinical remission (median 1 [IQR 1-2]) (P < 0.001). However, abnormal FDG uptake often remained present in patients who were considered to be in clinical remission, particularly in the bone marrow (70%), lymph nodes (35%), lungs (20%), and arteries (10%). When comparing those with active disease according to the VEXAS syndrome clusters, we observed a trend towards more abnormalities in the inflammatory cluster (n=17; median 3 [IQR 2-5]) and the hematological/myelodysplasia cluster (n=24; median 3 [IQR 2-4]), compared to the mild-to-moderate cluster (n=7; median 1 [IQR 1-4]) (P=0.09).

Conclusion: We report on [¹⁸F]-FDG-PET/CT imaging results among patients with VEXAS syndrome. Although zones of abnormal FDG uptake occurred frequently in VEXAS syndrome, the abnormalities were mostly non-specific. More abnormalities were detected among those with active disease, but bone marrow hypermetabolism in particular often persisted in those considered to be in remission, suggesting subclinical disease activity.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/abnormalities-detected-with-18f-fdg-pet-ct-imaging-in-vexas-syndrome/