Relation between uroporphyrin excretion, acute attacks of hereditary coproporphyria and successful treatment with haem arginate

A homoallelic FECH mutation in a patient with both erythropoietic protoporphyria and palmar keratoderma

BACKGROUND

Erythropoietic protoporphyria (EPP) is a hereditary disorder caused by the deficiency of ferrochelatase (FECH) in the haem biosynthetic pathway. In the majority of families, EPP is transmitted as a pseudodominant trait. Autosomal recessive form of EPP is found in only about 3% of the families.

OBJECTIVES

In this study, we describe a 6-year-old boy who suffered from both EPP and palmar keratoderma.

METHODS AND RESULTS

A novel homoallelic missense mutation (p.Ser318Tyr) was identified in the FECH gene. In addition, a region of homozygosity of approximately 6.8 Mb was observed in chromosome 18 of the patient by both microsatellite and SNP array. The parents of the patient, both of Palestinian (Jordanian) origin, were heterozygous for the S318Y mutation, although no history of consanguinity was known. Microsatellite genotyping identified a partial haplotype from each parent that corresponds to the region of homozygosity in the patient. Assuming S318Y is a founder mutation, the number of generations separating the two parents from their common ancestor from whom they inherited S318Y was estimated as 21.7 (95% CI 3.42–69.7).

CONCLUSION

EPP was therefore inherited as an autosomal recessive trait in the family. This study confirms the association between palmar keratoderma and autosomal recessive EPP.

Hereditary coproporphyria in Germany: clinical-biochemical studies in 53 patients

OBJECTIVES

To describe the biochemical and clinical features in hereditary coproporphyria (HCP).

DESIGN AND METHOD

Within the last 20 years, we investigated 53 patients (male:female = 1:2.5; age = 8-86 years) suffering from HCP. We describe the characteristic levels of urine, and fecal porphyrins and their precursors in hereditary coproporphyria and present the clinical features. Especially, we measured the coproporphyrin isomers I and III.

RESULTS AND CONCLUSION

The group of hereditary coproporphyria patients exhibited a significantly higher (p<0.0001) excretion of urinary porphyrin precursors, delta-aminolevulinic acid (median = 84 micromol/24 h) and porphobilinogen (median = 39 micromol/24 h), as compared to controls (delta-aminolevulinic acid: 22 micromol/24 h, porphobilinogen: 3 micromol/24 h; median, n = 20). The median of coproporphyrin in urine (1315 nmol/24 h) and feces (1855 nmol/g) were enhanced 12- and 168-fold, as compared to healthy subjects (urinary coproporphyrin: 106 nmol/24 h, fecal coproporphyrin: 11 nmol/g; median, n = 20). During therapy on one female patient, with IV application of heme arginate, a considerable decline of porphyrin precursors and porphyrin excretion was observed. The examination of urinary and fecal coproporphyrin isomers I and III revealed an excessive elevation of the coproporphyrin isomer III of 87% in urine and 94% in feces, respectively (normal: urinary isomer III = 69-83% and fecal isomer III = 25-40%). In feces the increase of isomer III caused an inversion of the physiologic coproporphyrin isomer III:I ratio that could be recognized in all various stages in hereditary coproporphyria and in children. Acute attacks of hereditary coproporphyria are accompanied by an acute polysymptomatic clinical syndrome, and this is associated with high levels of urinary porphyrin precursors. On review of our patients, the highest percentage had abdominal pain (89%), followed by neurologic (33%), psychiatric (28%), cardiovascular (25%), and skin symptoms (14%).

Biochemical differentiation of the porphyrias

OBJECTIVES

To differentiate the porphyrias by clinical and biochemical methods.

DESIGN AND METHODS

We describe levels of blood, urine, and fecal porphyrins and their precursors in the porphyrias and present an algorithm for their biochemical differentiation. Diagnoses were established using clinical and biochemical data. Porphyrin analyses were performed by high performance liquid chromatography.

RESULTS AND CONCLUSIONS

Plasma and urine porphyrin patterns were useful for diagnosis of porphyria cutanea tarda, but not the acute porphyrias. Erythropoietic protoporphyria was confirmed by erythrocyte protoporphyrin assay and erythrocyte fluorescence. Acute intermittent porphyria was diagnosed by increases in urine delta-aminolevulinic acid and porphobilinogen and confirmed by reduced erythrocyte porphobilinogen deaminase activity and normal or near-normal stool porphyrins. Variegate porphyria and hereditary coproporphyria were diagnosed by their characteristic stool porphyrin patterns. This appears to be the most convenient diagnostic approach until molecular abnormalities become more extensively defined and more widely available.

Studies on coproporphyrin isomers in urine and feces in the porphyrias

The urinary and fecal distribution and the relative proportions of the four coproporphyrin (copro) isomers I-IV were analysed in 20 healthy subjects and in patients suffering from one of the seven common types of hepatic or erythropoietic hereditary porphyrias. The ratios of copro isomers I-IV were analyzed by ion-pair high-performance liquid chromatography (HPLC). Observations showed significantly increased proportions of fecal copro isomer I and decreased proportions of copro isomers III, II and IV in erythropoietic porphyrias. In acute hepatic porphyrias the excretion of fecal copro isomer III is dominant (isomer III = 58.4+/-24.0%; x+/-S.D.) and significantly higher (P < 0.001) than in erythropoietic porphyrias (isomer III = 15.3+/-7.7%; x+/-S.D.) and chronic hepatic porphyrias (isomer III = 25.8+/-7.6%; x+/-S.D.). The increased proportions of fecal copro isomer III proved to be important for the diagnosis of hereditary coproporphyria and porphyria variegata independent of the clinical phase existing. These last two acute hepatic porphyrias also showed markedly elevated percentages of the fecal atypical isomers II and IV. In urine significantly decreased proportions of copro isomer I in acute hepatic porphyrias (isomer I = 12.3+/-6.0%; x+/-S.D.) could be observed as compared with non-acute porphyrias (isomer I = 53.7+/-15.2%; x+/-S.D.). Conversely, the proportion of urinary copro isomer III was significantly higher in acute hepatic porphyrias (isomer III= 81.4+/-6.4%; x+/-S.D.). As expected, the greatest amounts of urinary copro isomer I were found in congenital erythropoietic porphyria (isomer I =92.0+/-3.3; x+/-S.D.) and protoporphyria with hepatobiliary complications (isomer I = 81.3+/-10.7; x+/-S.D.). The atypical urinary copro isomers I1 and IV were detected in all types of porphyrias ranging from 0.1 to 11.5%. The combined amounts of copro isomers II and IV show a significantly decreased percentage in congenital erythropoietic porphyria as compared with all other types of hereditary porphyrias. In conclusion, we demonstrate that the characteristic pattern of the copro isomer constellations I-IV in the various types of porphyrias are of differential diagnostic importance. The inversion of the I to III ratio in feces in hereditary coproporphyria and porphyria variegata allows the recognition of gene carriers.