Development of giant cell (temporal) arteritis in a patient 'adequately' treated for polymyalgia rheumatica.

A 70-year-old woman presenting with typical polymyalgia rheumatica (PMR) and a normal temporal artery biopsy appeared to respond completely to low-dose prednisone therapy. A subsequent biopsy showing temporal arteritis with a normal sedimentation rate and no recurrence of myalgic symptoms emphasizes the unpredictable course of treated PMR and the need for continued clinical as well as laboratory follow-up.