Circulating immunoblasts in polymyalgia rheumatica.

The percentage of immunoblasts circulating in the peripheral blood has been examined in a group of 29 patients with polymyalgia rheumatica (PMR). Less than 0.5% of immunoblasts were found in healthy young controls, but 18 of 29 unselected patients with PMR were positive when first tested, a similar proportion to that found in rheumatoid arthritis. Raised immunoblasts were found in only one of 12 elderly controls. The presence of circulating immunoblasts correlated with the activity of polymyalgia both as assessed by the erythrocyte sedimentation rate (ESR) and as assessed by an independent clinical observer. This was true in the group overall and in those patients where serial studies were made. Patients studied from the time of disease presentation showed a concurrent fall in ESR and in immunoblasts on starting steroid therapy. Detection of circulating immunoblasts can be a useful additional test in the assessment of disease activity in PMR, especially in cases with a low ESR. The presence of circulating immunoblasts supports the concept of an immunological aetiology for PMR. This is strengthened by the finding that raised immunoglobulins were more common in patients with circulating immunoblasts.