The diagnosis of polymyalgia rheumatica is made difficult by the absence of any pathognomonic findings. Erythrocyte sedimentation rate (ESR) and concentration of C-reactive protein are used as diagnostic criteria and to monitor the disease's course. It was the purpose of this study to evaluate prevalence of thrombocytosis and whether there is any correlation between thrombocytosis and ischaemic complications.
In a retrospective study the data of 23 patients (14 women, 9 men; mean age 67.3 [48-84] years) with polymyalgia rheumatica were analysed: platelet counts, ESR and C-reactive protein had been measured at the time of diagnosis and 7, 14 and 21 days after start of glucocorticoid treatment. At the time of diagnosis 17 of 23 patients (74%) had a thrombocytosis (> 400,000/microliter), at a mean value of 511,000 (418,000-638,000)/microliter. The platelet count decreased more slowly than the inflammatory parameters. On average the platelet count returned to normal on the 14th day. Ischaemic complications developed in three patients (visual disturbances, blindness, cardiac arrhythmias, neurological deficits): all had a high platelet count (462,000-524,000/microliter).
Thrombocytosis can serve as an additional criterion in the diagnosis and follow-up of polymyalgia rheumatica. An association with ischaemic complications is especially likely in the elderly, in case of immobility and if there is evidence of giant-cell arteritis. Treatment with platelet aggregation inhibitors should be considered.