Berlin · New York Composition of Urinary Coproporphyrin Isomers I —IV

Dedicated to Professor Claude Rimington in honour of his 90th birthday Summary: The urinary distribution and relative proportions of the four Coproporphyrin isomers I—IV were investigated in 50 patients suffering from hepatic and erythropoietic types of hereditary porphyrias. A highly efficient sample preparation method was applied to isolate urinary coproporphyrins, the isomer ratios of which were quantitated by isocratic ion-pair high-performance liquid chromatography. Results showed a significant decrease (p < 0.001) of the proportion of Coproporphyrin I in acute hepatic porphyria (acute intermittent porphyria, hereditary coproporphyria, variegate porphyria, porphobilinogen synthase deficiency porphyria) as compared with chronic hepatic porphyria (porphyria cutanea tarda, chronic hepatic porphyria type B and C) (13.2 ± 5.3%, χ ± S.D., vs. 31.4 ± 11.5%). Conversely, the proportion of isomer III was significantly higher (p < 0.001) in acute hepatic porphyria than in chronic hepatic porphyria (80.9 + 5.2% vs. 62.2 + 10.9%). As expected, the highest level of Coproporphyrin I (90.0 ± 1.9%) was found in congenital erythropoietic porphyria. The atypical coproporphyrins II and IV were detected in all types of porphyria analysed and ranged from 0.2 to 9.0%; no significant differences were seen between acute and chronic hepatic porphyrias. The diagnostic importance of the isomer ratios of coproporphyrins I and III has been confirmed in our study, while th