Heat induced radial segmentation of leukocyte nuclei in patients with polymyalgia rheumatica and other inflammatory diseases. Heat induced radial segmentation of leukocyte nuclei is an in vitro phenomenon accompanying inflammatory diseases. We studied 62 patients with suspected polymyalgia rheumatica (PMR) to determine, whether heat induced radial segmentation can help in discriminating PMR from other conditions. At the initial presentation patients with PMR had more radial segmentation formation than patients with other inflammatory conditions. Prednisone induced a rapid and marked decrease in radial segmentation formation in patients with PMR. This latter finding was much less marked in patients with other inflammatory conditions. We conclude that heat induced radial segmentation at the initial presentation and during prednisone treatment can help in discriminating PMR from other inflammatory conditions. 