DECREASED UROPORPHYRINOGEN DECARBOXYLASE ACTIVITY IN PATIENTS WITH END-STAGE RENAL-DISEASE UNDERGOING HEMODIALYSIS

Raised plasma uroporphyrin levels were found in all the 14 patients wi th end-stage renal disease studied, 7 of whom were on continuous ambul atory peritoneal dialysis (CAPD) and 7 on hemodialysis (HD). The eleva tion observed in the HD group was higher than that noted in the CAPD g roup; 18-fold in the former and 13-fold in the latter. The difference in uroporphyrin plasma levels between the two dialysis populations mig ht be explained, at least partially, by the reduced activity of uropor phyrinogen decarboxylase (UROD), the enzyme which converts uroporphyri nogen to coproporphyrinogen. A decrease of 48 % was noted in the HD gr oup, whereas no change was observed in the CAPD group. A significant n egative correlation (r = -0.37, p < 0.01) was found between the concen tration of uroporphyrin in plasma and the activity of UROD. In view of the data shown, it is suggested that erythrocyte UROD activity should be interpreted with caution in HD patients suspected of having porphy ria cutanea tarda.