Faecal coproporphyrin isomers in hereditary coproporphyria

Abstract

Hereditary coproporphyria (HC) is an acute porphyria. Acute attacks with neurological and psychiatric symptoms may be precipitated by some drugs. Our aim was to determine if the faecal Coproporphyrin III: Coproporphyrin I (CIII:CI) isomer ratio by high performance liquid chromatography would be suitable to identify patients at risk. We determined the faecal CIII:CI ratio in 38 persons belonging to one large and two smaller families with HC and compared the results with the activity in the lymphocytes of copro-porphyrinogen oxidase (COPOX)#, the enzyme deficient in the livers of patients with HC. All adults with normal COPOX (>180 pmol/mg protein/hour) had normal CHI:CI ratios (<1.3) and those with low COPOX (<150 pmol/mg protein/hour) had CIII: CI ratios >2. The results were difficult to interpret in six of the 10 children where we found borderline or low COPOX (relative to the adult reference range) in the presence of a normal faecal CHI:CI ratio. We found abnormal CIH:CI ratios in five subjects who had normal faecal total porphyrin but low COPOX indicating that the measurement of total faecal porphyrin alone is inadequate for a family study. The determination of the faecal CHI: CI ratio is less invasive, more convenient, cheaper and technically easier than the determination of lymphocyte COPOX activity. We conclude that the determination of the faecal CIII:CI ratio is suitable for family studies of HC. ^#Guo R.Lim CK, et al. Clin Chim Acta 1988;177: 245-52