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1/5. Biochemical and genetic characterization of four cases of hereditary coproporphyria in spain.

    We report a biochemical and genetic characterization of four cases of hereditary coproporphyria (HCP) in spain. All patients showed a typical HCP porphyrin excretion pattern with a high concentration of coproporphyrins in feces and inverted I:III isomer ratio. The porphyrin precursors in urine were found elevated in two patients who showed acute symptoms. The analysis of the CPO gene showed that three cases harboured novel mutations: V135A (404T>C; exon 1); L214R (641T>G; exon 2); and P249R (746C>G; exon 3) and in the fourth, a previously described R426X mutation in exon 6. ( info)

2/5. Mutations in human CPO gene predict clinical expression of either hepatic hereditary coproporphyria or erythropoietic harderoporphyria.

    Hereditary coproporphyria (HCP), an autosomal dominant acute hepatic porphyria, results from mutations in the gene that encodes coproporphyrinogen III oxidase (CPO). HCP (heterozygous or rarely homozygous) patients present with an acute neurovisceral crisis, sometimes associated with skin lesions. Four patients (two families) have been reported with a clinically distinct variant form of HCP. In such patients, the presence of a specific mutation (K404E) on both alleles or associated with a null allele, produces a unifying syndrome in which hematological disorders predominate: 'harderoporphyria'. Here, we report the fifth case (from a third family) with harderoporphyria. In addition, we show that harderoporphyric patients exhibit iron overload secondary to dyserythropoiesis. To investigate the molecular basis of this peculiar phenotype, we first studied the secondary structure of the human CPO by a predictive method, the hydrophobic cluster analysis (HCA) which allowed us to focus on a region of the enzyme. We then expressed mutant enzymes for each amino acid of the region of interest, as well as all missense mutations reported so far in HCP patients and evaluated the amount of harderoporphyrin in each mutant. Our results strongly suggest that only a few missense mutations, restricted to five amino acids encoded by exon 6, may accumulate significant amounts of harderoporphyrin: D400-K404. Moreover, all other type of mutations or missense mutations mapped elsewhere throughout the CPO gene, lead to coproporphyrin accumulation and subsequently typical HCP. Our findings, reinforced by recent crystallographic results of yeast CPO, shed new light on the genetic predisposition to HCP. It represents a first monogenic metabolic disorder where clinical expression of overt disease is dependent upon the location and type of mutation, resulting either in acute hepatic or in erythropoietic porphyria. ( info)

3/5. Clinical indications for the investigation of porphyria: case examples and evolving laboratory approaches to its diagnosis in new zealand.

    patients with porphyria present in a diverse and unusual variety of ways and most clinicians will see only a few cases, if any, during their professional lives. Porphyria may present (1) with acute symptoms, which may be abdominal pain, neurological or psychiatric; (2) with skin rash or photosensitivity; or (3) with a putative family history. Screening for latent porphyria has been greatly facilitated by fluorescence emission scanning of plasma and by mutational analysis. Our reference laboratory has recently diagnosed several cases of the less common types of porphyria, which we postulate is due to the availability of these methods and to the changing population of new zealand. Accurate screening and diagnosis of porphyria is important, as an acute porphyric attack is life-threatening and preventable. Retrospective diagnosis may be difficult. ( info)

4/5. Dual gene defects involving delta-aminolaevulinate dehydratase and coproporphyrinogen oxidase in a porphyria patient.

    Summary A Caucasian male had symptoms of acute porphyria, with increases in urinary delta-aminolaevulinic acid (ALA), porphobilinogen (PBG) and coproporphyrin that were consistent with hereditary coproporphyria (HCP). However, a greater than expected increase in ALA, compared with PBG, and a substantial increase in erythrocyte zinc protoporphyrin, suggested additional ALA dehydratase (ALAD) deficiency. Nucleotide sequence analysis of coproporphyrinogen oxidase (CPO) cDNA of the patient, but not of the parents, revealed a novel nucleotide transition G835-->C, resulting in an amino acid change, G279R. The mutant CPO protein expressed in escherichia coli was unstable, and produced about 5% of activity compared with the wild-type CPO. Erythrocyte ALAD activity was 32% of normal in the proband. Nucleotide sequence analysis of cloned ALAD cDNAs from the patient revealed a C36-->G base transition (F12L amino acid change). The F12L ALAD mutation, which was found in the mother and a brother, was previously described, and is known to lack any enzyme activity. This patient thus represents the first case of porphyria where both CPO and ALAD deficiencies were demonstrated at the molecular level. ( info)

5/5. delayed diagnosis of porphyria based on manifestations of systemic lupus erythematosus and ankylosing spondylitis.

    In this case report, a patient with systemic lupus erythematosus and ankylosing spondylitis is presented, who was diagnosed with hereditary coproporphyria after 5 years of follow-up. Diagnostic difficulties and possible role of genetic background in the autoimmune response in patients with porphyria are briefly discussed. ( info)


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