To identify inflammatory pelvic structures of patients with polymyalgia rheumatica (PMR) by magnetic resonance imaging (MRI) in detail, searching for a disease-specific pattern.
A total of 40 contrast-enhanced pelvic MRIs of patients with a clinical diagnosis of PMR was reviewed by an experienced musculoskeletal radiologist who assessed all abnormalities semi-quantitatively, based on a predefined scoring system.
The median (25th/75th percentiles) age of patients was 67 (55/73) years, median symptom duration 13 (6/22) weeks, 55% female, median CRP 1.9 (0.7/4) mg/dl, median ESR 30/1h (17/43). Ten patients were diagnosed with rheumatoid arthritis (25%), in addition to their leading polymyalgic symptom. Multi-locular, mostly bilateral, peritendinous enhancement of pelvic girdle tendons was found to be the hallmark of PMR in all patients. Low-grade hip synovitis was also detected frequently. In all cases, ≥4 extracapsular tendinous sites were bilaterally affected. Besides involvement of the common ischiocrural tendon and the glutaeus medius and minimus tendon (present in all cases), an enhancement of the proximal rectus femoris origin was observed in 100% and of the adductor muscles at the inferior medial pubic bone in 90% of cases. The observed MRI pattern patho-anatomically suggests inflammation of the external peritendineum.
The uniformity of the observed pelvic inflammatory pattern detected by contrast-enhanced MRI in PMR patients suggests that it may become relevant for diagnostic purposes. The bilateral involvement of at least 4 extracapsular sites (including the origins of proximal rectus femoris or adductorial muscles) appears to be characteristic of PMR.