Background/Purpose: Polymyalgia rheumatica (PMR) is a common inflammatory condition of elderly persons. Clinical symptoms respond to low-dose glucocorticoids, but treatment is often required for several years. The recent UK guideline and a systematic review reported the adequate initial dose of prednisolone (PSL) was 15 or 20 mg daily. PSL doses as mg/kg body weight (PSL/BW) might be too large in lighter-build patients. Majority of PMR patients in Japan are smaller and lighter than the patients in Western countries.

We evaluated the initial doses of PSL and clinical course of the Japanese patients.

Methods: This was a retrospective study in a single hospital. We studied 15 patients with a diagnosis of PMR according to modified Bird’s criteria (CRP positive instead of ESR>40). They presented to our hospital from April 2011 to April 2013. Patients who had the following symptoms were excluded; recent temporal or occipital pain, tender, swollen temporal artery, jaw claudication, and impairment of vision.

The patients were divided into 2 subgroups based on the initial PSL/BW: less than 0.3 mg/kg PSL (group L) and more than 0.3 mg/kg (group H). Remission was defined as the absence of symptoms more than one month after the withdrawal of PSL. Relapse was defined by the recurrence of clinical symptoms accompanied by serum CRP elevation, requiring PSL increase. We collected the demographic and clinical data from the medical records.

Statistical significance of differences between two groups of patients was determined by Mann-Whitney U test and chi-squared test. Analyses were performed using JMP ver9.

Results: The median follow-up was 14 months (range 2 to 18 months). Among the 15 patients, ten were women. Nine of 10 women and 1 of 5 men were weighing less than 50 kg. PSL Initial doses were 15 mg in 7 patients, 5mg in 5 patients, 20mg in 2 patients, and 5mg in 1 patient. The mean PSL/BW was 0.29 mg/kg/day. Eight patients belonged to group L, the other to group H. There was no significant difference in follow-up months, sex, age, BW, and serum CRP at diagnosis between two groups. In addition, the clinical course, including the relapse and PSL withdrawal rate, were similar in two groups.

Conclusion: Initial dose of PSL/BW < 0.3mg/kg was equally effective to that of PSL/BW >0.3mg/kg. Calculating the initial PSL dose by BW might be more appropriate for especially elderly low-body weight women in Japan without deteriorating their prognosis.