Outcome and follow-up
Prior to the autoimmune serology results becoming available, a clinical
diagnosis of PMR was made. This was based on the elevated inflammatory
markers, typical joint involvement and symptoms, and patient
demographic. The differential diagnoses included other autoimmune
arthritis such as RA or seronegative spondyloarthropathy. The
inflammatory arthritis was thought to be secondary to denosumab given
the time course of symptom onset soon after the injection.
Early in the admission, the patient was started on celecoxib with
minimal improvement. Given the suspicion for PMR, he was subsequently
started on 10 mg prednisolone once daily. There was a remarkably good
response the following day, with the patient returning to full range of
motion in his right shoulder as well as noting significant reduction in
musculoskeletal pain.
The uptrending CRP began to decrease after starting prednisolone–the
level was 235.2 mg/L the day prior to initiating therapy, and declined
to 178.9 mg/L one day after the initial 10 mg dose. He was discharged
after two days with a slow weaning dose of prednisolone and planned for
rheumatology clinic follow-up. The patient was advised to switch to a
different osteoporosis treatment.
The subsequently available results of an elevated RF and ACPA led to the
revised diagnosis of denosumab-induced seropositive inflammatory
arthritis with overlapping features of late-onset RA and PMR.