Uremic pruritus: skin divalent ion content and response to ultraviolet phototherapy

Pruritus is a frequent and troublesome consequence of end-stage renal disease. We have surveyed 155 chronic dialysis patients and found pruritus to be a significant problem in approximately 70%. Seventeen patients reporting severe pruritus were treated thrice weekly with total body exposure to either UVA or UVB light. UVB light resulted in resolution of pruritus in all cases. UVA light was without significant effect. Skin biopsies obtained before and after UV phototherapy revealed elevated contents of calcium, magnesium, and phosphorus in all pruritic patients. The resolution of pruritus following UVB treatment was associated with a reduction of skin phosphorus to values comparable with nonpruritic uremics or healthy volunteers. Uremic pruritus may be due to increased skin divalent ion content resulting in microprecipitation of calcium or magnesium phosphate.