FDG-PET/CT in patients with ANCA-associated vasculitis: Case-series and literature review

We aimed to assess the clinical value of FDG-PET/CT in patients with ANCA-associated vasculitis. We retrospectively included 16 patients with ANCA-associated vasculitis who underwent 21 FDG-PET/CT between 2009 and 2013, in 2 university hospitals from the Paris suburb area. All FDG-PET/CTs were retrospectively analyzed and compared to clinical, biological and conventional imaging data at baseline and during the follow-up. ANCA-associated vasculitis was granulomatosis with polyangiitis (GPA, n = 10), microscopic polyangiitis (MPA, n = 4), and eosinophilic GPA (EGPA, n = 2). PET was performed at initial presentation in 14 cases and during the follow-up in 7 cases. At baseline, PET was positive in 100% of GPA patients (8/8) and in 50% (3/6) of patients with other ANCA-vasculitis (p = 0.05). FDG uptake tended to be higher in patients with GPA in comparison to patients with MPA/EGPA (median SUVmax: 5 versus 2.5; p = 0.08). Sinonasal, lung, cardio-vascular and kidney involvements were all accurately identified by PET, except in one MPA patient with glomerulonephritis. As expected, skin, joint, eye and peripheral nervous system impairments were not detected by PET. No occult site was detected by PET, except in 2 salivary gland FDG uptake without clinical abnormalities. Patients with GPA exhibited a higher number of positive sites on PET (2 [1.75–2.25] versus 0.5 [0–1], p = 0.006) than patients with MPA/EGPA. In pooled data including our study and the literature data of GPA patients (n=31), SUVmax was associated with Birmingham Vasculitis Activity Score (BVAS) (r=0.49; p=0.03). FDG-PET/CT accurately identifies organ localizations in GPA, other than in nervous system, eye and skin, but do not bring additional benefit to the usual organ screening. The value of FDG-PET/CT in other ANCA-associated vasculitis need to be further addressed.