Quantitative observations on iliac bone marrow mast cells in chronic renal failure

Mast cells have been counted in sections of iliac bone from 61 control subjects at necropsy. Mast cells were found in all but three, and the range was 0-33-7, median 1-95 per mm2 marrow. The majority (82%) had less than 4-99 mast cells per mm2 marrow; in 37-7% there was less than 1 mast cell per mm2 marrow. In a group of 45 patients with chronic renal failure there was a significant increase in the numbers of mast cells (P less than 0-001) with a range of 0-96-55-63, median 9-55 per mm2 marrow. Mast cells were common in the areas of marrow fibrosis associated with osteitis fibrosa but this was not the sole cause of the increase since there was also an excess of mast cells in the non-fibrous parts of the marrow. There was a tendency towards greater numbers of mast cells in those cases with most marked osteitis fibrosa in association with the prominent marrow fibrosis, but there was no significant relationship between mast cell numbers and other features of oesteitis fibrosa such as the number of osteoclasts and the amount of woven bone formation. There was no relationship between the numbers of mast cells and the amounts of total bone, ostoid, percentage mineralization of cancellous bone, or the presence of osteomalacia.