To characterize ankle magnetic resonance imaging (MRI) features in pediatric and young adult patients with familial Mediterranean fever (FMF) and compare them with those in juvenile idiopathic arthritis (JIA) and chronic nonbacterial osteomyelitis (CNO) in order to identify distinguishing or overlapping imaging features among the three conditions. Twelve ankle MRI examinations from 11 patients with FMF (mean age 12.4 years, 7 females) were retrospectively evaluated and compared with 22 examinations from 17 patients diagnosed with JIA (12 patients/14 ankles, mean age 14.3 years, 8 females) or CNO (5 patients/8 ankles, mean age 10.2 years, 3 females). Calcaneal enthesitis features were assessed at the insertion site of the Achilles tendon, plantar fascia, and the long plantar tendon. Also evaluated were the presence of diffuse calcaneal bone marrow edema (BME), midfoot arthritis, synovitis, and tenosynovitis. Insertional calcaneal BME, an enthesitis-related feature, was more prevalent in FMF patients compared to both JIA and CNO, while among the three evaluated entheses, long plantar tendon enthesitis was significantly more prevalent in FMF patients only compared to those with JIA ( p < 0.001). CNO presented a predominantly osseous inflammation pattern with diffuse calcaneal BME (87.5%, p < 0.001) and additional hindfoot BME (75%, p < 0.002), clearly distinct from FMF. Synovitis and tenosynovitis were more commonly observed in JIA patients, although the differences compared to FMF and CNO were not statistically significant. Although imaging features overlap among FMF, CNO, and JIA, distinct MRI patterns emerge: enthesitis predominates in FMF, osteitis in CNO, and synovitis in JIA.
Kraus et al. (Wed,) studied this question.