Whole-body MRI of patients with polymyalgia rheumatica identifies a distinct subset with complete patient-reported response to glucocorticoids

Objectives To determine whether whole-body MRI
defines clinically relevant subgroups within polymyalgia
rheumatica (PMR) including glucocorticoid
responsiveness.
Methods 22 patients with PMR and 16 with rheumatoid
arthritis (RA), untreated and diagnosed by consultant
rheumatologists, underwent whole-body, multiple-joint
MRI, scored by two experts. Patients with PMR reported
whether they felt ‘back to normal’ on glucocorticoid
therapy and were followed for a median of 2 years.
Results All patients with PMR were deemed to respond
to glucocorticoids clinically. A characteristic pattern of
symmetrical, extracapsular inflammation, adjacent to
greater trochanter, acetabulum, ischial tuberosity and/or
symphysis pubis, was observed in 14/22 of the PMR cases.
In PMR, this pattern was associated with complete
glucocorticoid response (p=0.01), higher pretreatment Creactive
protein (CRP) and serum interleukin-6 (IL-6), and
better post-treatment fatigue and function. Only 1/14 in
the extracapsular group could stop glucocorticoids within
1 year, compared with 4/7 of the others. A score derived
from the five sites discriminating best between PMR and
RA correlated with IL-6 (p<0.002). IL-6 levels ≥16.8 pg/
mL had 86% sensitivity and 86% specificity for the
extracapsular MRI pattern.
Conclusions A subset of patients with rheumatologistdiagnosed
PMR had a characteristic, extracapsular pattern
of MRI inflammation, associated with elevated IL-6/CRP
and with complete patient-reported glucocorticoid
responsiveness.