Late-Onset RA vs PMR — SCE Rheumatology MCQ

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ModerateVasculitisLate-Onset RA vs PMRSCE Rheumatology

A 75-year-old woman has an 8-week history of bilateral shoulder and hip-girdle pain with morning stiffness lasting 90 minutes. Her ESR and CRP are raised. She was initially diagnosed with polymyalgia rheumatica, but subsequent testing shows a high-titre anti-CCP antibody. Which alternative diagnosis should be strongly considered?

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Correct answer: E — Late-onset rheumatoid arthritis

Late-onset rheumatoid arthritis is correct. Rheumatoid arthritis beginning in later life may have a polymyalgic phenotype, with acute proximal pain and stiffness and raised inflammatory markers. Anti-CCP antibodies are usually absent in PMR; a high-titre positive result in this context strongly favours late-onset RA. Peripheral synovitis or tenosynovitis should be sought clinically and with ultrasound. Anti-CCP positivity alone does not confirm RA without compatible joint disease, so the diagnosis should be strongly considered rather than regarded as established. Fibromyalgia does not explain raised inflammatory markers. Hypothyroidism and polymyositis may cause proximal symptoms but more typically produce weakness or biochemical muscle abnormalities and do not explain anti-CCP positivity. Malignancy can mimic PMR, but the serology specifically points towards RA. Glucocorticoid response is not a reliable discriminator because both conditions may improve.

Reference: Lopez-Hoyos M et al. Clinical utility of anti-CCP antibodies in the differential diagnosis of elderly-onset rheumatoid arthritis and polymyalgia rheumatica. Rheumatology (Oxford). 2004;43:655-657. https://pubmed.ncbi.nlm.nih.gov/14970400/