Dermal mast cell density and pruritus in end-stage renal failure.

Skin mast cell density was determined in two age- and sex-matched groups of patients with end-stage renal failure, one with severe uraemic pruritus (n = 9) and the other without (n = 9). In each group, seven patients were on chronic haemodialysis. In uraemic patients without pruritus, skin mast cell density was similar to that in eight healthy controls (40.1 +/- 10.2 mm2 versus 46.5 +/- 20.6 mm2; P = 0.44), a result also obtained when only the patients on haemodialysis were considered (39.3 +/- 14.7 versus 46.5 +/- 20.6; P = 0.46), showing that haemodialysis per se did not cause mast cell proliferation. In contrast, uraemic patients with itch had significantly higher dermal mast cell counts when compared with those without itch (71.8 +/- 36.4 mm2 versus 40.1 +/- 12.9 mm2; P = 0.01). However, there was no difference in serum parathyroid hormone (PTH) and calcium or phosphate concentrations between the two groups. In addition, there was no significant correlation between dermal mast cell density and serum PTH, calcium or phosphate concentrations. These data suggest that uraemic pruritus may be related to mast cell proliferation in the skin.