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A 7-year-old boy demonstrating hepatosplenomegaly, mild anaemia, mild mental retardation, yellow-brown teeth and dark red urine had excessively elevated levels of urinary delta-aminolevulinic acid, porphobilinogen and uroporphyrin. Furthermore hepta-, hexa-, penta- and copro(I)porphyrins were highly increased in urine. This pattern of porphyrin precursor and metabolite excretion is characteristic of acute intermittent porphyria. The decreased copro(III)/copro(I+III) ratio, normally not found in acute intermittent porphyria, is discussed. The porphobilinogen deaminase activity in red cells was decreased to 2-4%. Mutation analysis revealed a novel homozygous L81P mutation in exon 6 of the porphobilinogen deaminase gene. The father and mother, shown to be gene carriers of the same mutation, are asymptomatic and have normal urinary porphyrin precursor and metabolite excretion.

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We studied precision and accuracy of a HPLC method for determination of porphyrins in feces. A commercial standard solution appeared to contain less coproporphyrin (15%) than stated by the manufacturer. The between-batch coefficients of variation were often below 15% and were higher than the within-batch coefficients. The precision of porphyrin measurements was not influenced by the type of porphyria. Recoveries of added coproporphyrin and protoporphyrin were 90% and 108%; coefficients of variation were 6% and 19%, respectively.

We studied the accuracy and precision of a HPLC method for determination of porphyrins in urine. A commercial standard solution appeared to contain less porphyrins than indicated by the manufacturer, since calibration resulted in lower concentrations of uroporphyrin and coproporphyrin: 16% and 8%, respectively. Coefficients of variation for the measurement of uro-, hepta-, copro I and copro III porphyrins in samples of patients with and without porphyria were often much less than 15%. Comparison of measurements with and without calibrated standards revealed differences for uroporphyrin and coproporphyrin of 27% and 5%, respectively. Recovery of added uroporphyrin and coproporphyrin was 99%. The main cause of the variability in test results was apparently the improperly calibrated standard solutions. The precision of porphyrin measurements was not influenced by the type of porphyria.