Clinical porphyrin analyses: indications and interpretations

Biochemical and molecular diagnosis of erythropoietic protoporphyria in an Ashkenazi Jewish family

Erythropoietic protoporphyria (EPP) is a rare hereditary disorder due to a partial deficiency of ferrochelatase (FECH). The genotype of EPP patients features a mutation on one allele of the FECH gene and a common hypomorphic FECH IVS3-48c on the other allele (M/c). The resulting enzyme activity in patients is ∼35% of that in normal individuals. Ferrochelatase deficiency results in the accumulation of protoporphyrin in the skin, which is responsible for the clinical symptom of cutaneous photosensitivity in patients. In this study, we report the identification of a novel FECH mutation delT23 in an 11-member EPP family of Jewish origin. Two EPP siblings shared an identical genotype of delT23/IVS3-48c (M/c). They were both photosensitive and showed highly increased erythrocyte protoporphyrin. The genotype of the patients' mother, who did not present with any EPP clinical symptoms, was delT23/IVS3-48t (M/t). The patients' father, an offspring of consanguineous parents, was homozygous IVS3-48 c/c. He exhibited a mild photosensitivity, and an increase of 4-fold in erythrocyte protoporphyrin. His FECH mRNA amount was 71% of that of genotype t/t. It is the first reported case of an individual with c/c genotype who exhibits both biochemical and clinical indications of EPP. These results suggest that IVS3-48c is a functional variant of ferrochelatase. The clinical symptoms and biochemical abnormalities in the patients' father could be the result of an interaction between genetic and environmental factors. In addition, the frequency of IVS3-48c in the Ashkenazi Jewish population was estimated at 8%, which is similar to that in the European populations.

Experimental latent and acute porphyria in the non-fasted rat; preventive effect of propranolol

This study demonstrates an experimental model of the biochemical pattern of the 'latent phase' of hepatic porphyria subject to 'acute attack', upon application of prophyrinogenic stimuli. The 'latent phase' was achieved by administering 3,5-diethoxycarbonyl-1, 4-dihydrocollidine [DDC], 70 mg kg-1 day, orally to non-fasted rats. A two- and threefold increase in coproporphyrin in urine and protoporphyrin in faeces, respectively, were observed. An 'acute attack' was induced by phenobarbitone (PB), 100 mg kg-1, administered on the third day of treatment with DDC, followed by administration of 2-allyl-2-isopropylacetamide (AIA), 470 mg kg-1, on the fourth day. A fourfold elevation in urinary porphobilinogen (PBG) and delta-aminolevulinic acid (ALA) and further increase of three- and fourfold in urinary coproporphyrin and faecal protoporphyrin, respectively, was observed. The effect of DDC, AIA and PB on the excretion of PBG and porphyrins was found to be synergistic rather than additive. dl-Propranolol, 700 mg kg-1, given to DDC treated rats 'latent phase' reduced the amount of porphyrins excreted in urine and faeces to those observed in control dimethyl sulphoxide (DMSO) treated rats. It also prevented induction of 'acute attack' caused by the combination of PB and AIA. It is shown that dl-propranolol affects a few parameters in the haem biosynthetic pathway. Its beneficial effect in porphyria is probably the result of increasing the concentration of haem in the free haem pool.