The spectrum of polymyalgia rheumatica in Northwestern Spain: Incidence and analysis of variables associated with relapse in a 10 year study

Objective. To examine patients presenting with polymyalgia rheumatica (PMR) during a 10 year period in Northwestern Spain and to assess disease incidence and the frequency of relapses in patients diagnosed as having either isolated ('pure') PMR or PMR associated with giant cell arteritis (GCA). Methods. Clinical records of patients with PMR diagnosed at the Hospital Xeral Lugo from January 1987 through December 1996 were reviewed. Patients with PMR were categorized into 2 subgroups depending on the presence or absence of associated GCA. Other conditions presenting with polymyalgia symptoms or mimicking isolated PMR were excluded. These patients were followed from the time of diagnosis until either patient's death or January 1, 1998. Results. One hundred eighty-five patients were studied. The average annual incidence rates of the total group of PMR and isolated PMR were 18.67 x 10-5 and 13.52 x 10-5, respectively, in a population aged 50 years or older. Relapses were frequent in both isolated PMR and PMR associated with GCA. In general, they occurred when the dose of prednisone was < 7.5 mg/day or it had been discontinued. Rate of steroid tapering was significantly higher in patients with isolated PMR who had relapses. Patients with HLA- DRB1*0401 had a higher frequency of relapses. As reported in patients with PMR associated with GCA, the adjusted mortality rate in patients with isolated PMR showed no difference compared to the Spanish population aged 50 years or older. Conclusion. In Northwestern Spain, PMR is a nonfatal disease with a low incidence and frequent relapses. A possible influence of HLA- DRB1*04 alleles in the development of more severe disease, with greater tendency to relapses, is suggested.