Age-dependent reference values of urinary porphyrins in children.

To establish age-dependent reference ranges for the 3 major urinary porphyrins, uroporphyrin, coproporphyrin I and coproporphyrin III, concentrations were measured in random urine specimens from 198 children aged 0.5 to 16 and 18 new-borns by HPLC. All three porphyrins displayed unique age-dependencies. The highest coproporphyrin I concentration was observed in the new-born period, which could be explained by a physiologically under-developed excretion system (via bile and faeces) for this particular porphyrin. Coproporphyrin III excretion reached its highest value in children between ages 1 and 2. Of the three porphyrins, coproporphyrin III concentration showed the closest correlation with the total haem synthesis in childhood. A relatively broad concentration range was found for uroporphyrin in all tested age-groups, the highest mean concentration being in the new-born period. Quantification of each individual urinary porphyrin enables the diagnosis of certain disorders which otherwise cannot be achieved by the total porphyrin determination. As an example of the clinical application of these reference ranges, a case of bronze baby syndrome is discussed.