Hereditary coproporphyria is biochemically distinct from the other
porphyrias and is characterized by excessive excretion of coproporphyrin in faeces and usually in urine. The laboratory findings in 28 patients with this disease are presented and the clinical details of eight patients who have been in attack summarised. The remaining 20 patients were latent for the disease. In all patients studied the activity of delta-aminolaevulinic
acid synthase was raised and
coproporphyrinogen oxidase depressed in the leucocyte. This indicates the partial
enzyme block in the
haem biosynthetic pathway in this disease. The activities of the other
enzymes in the pathway, leucocyte
ferrochelatase and erythrocyte delta-aminolaevulinic
acid dehydratase,
porphobilinogen deaminase and
uroporphyrinogen decarboxylase showed no consistent change. On review of 111 cases, 35 per cent presented in acute attack: 80 per cent had
abdominal pain, 34 per cent
vomiting, 29 per cent solar sensitivity, 23 per cent neurological involvement, 23 per cent psychiatric symptoms and 20 per cent severe
constipation. Only two fatalities have been published, both from
respiratory failure. There was a female preponderance of cases in attack of 2-5:1 and in the latent cases of 1-5:1 suggesting hormonal provocation in the uncovering of the disease. Drugs were implicated as precipitating 54 per cent of acute attacks and in 34 per cent of cases, these were
barbiturates. This study demonstrates the reduction in activity of
coproporphyrinogen oxidase in the
haem biosynthetic pathway and the elevation of delta-aminolaevulinic
acid synthase in the peripheral blood. These features, together with the typical abnormal
porphyrin excretion pattern, appear to be diagnostic of
hereditary coproporphyria whether in attack, remission, or in the latent form.