Porfiria cutánea tarda familiar: Presentación de un caso y revisión de la literatura / Cutaneous porphyria tarda familiar: presentation of a case and review of the literature

La porfiria cutánea tarda (PCT) es una enfermedad metabólica, crónica, que se produce por fallas en el metabolismo del hemo, debidas a deficiencia en la actividad de la enzima URO decarboxilasa. Se produce con más frecuencia en el sexo masculino y en adultos de mediana edad. Se clasifica en adquiridas y familiares, estas últimas de menor frecuencia, de acuerdo al antecedente familiar y al sitio de actividad de la enzima UROD. Las manifestaciones clínicas características son fragilidad cutánea, hipertricosis, fotosensibilidad y ampollas en áreas fotoexpuestas. El tratamiento de la enfermedad consiste en discontinuar los factores desencadenantes, reducir la sobrecarga hepática de hierro a través de flebotomías o el uso de antipalúdicos para movilizar el exceso de porfirinas. Presentamos el caso de una paciente femenina, con antecedente materno de PCT, que presentó manifestaciones clínicas en la adolescencia, asociado a factores desencadenantes y con excelente respuesta al tratamiento con flebotomías (AU)

Porphyria cutanea tarda (PCT) is a chronic metabolic disease caused by failures in heme metabolism, due to deficiency in the activity of the enzyme URO decarboxylase. Men and middle-age adults are often more affected. According to family history and the site of enzyme activity, PCT is classified in acquired or familial. Clinical features are skin fragility, hypertrichosis, photosensitivity and blisters on sun-exposed areas. Treatment of this disease is based on discontinuing the triggers, reduce liver iron overload trough phlebotomies or the use of antimalarial agents to mobilize excess porphyrins. A case of a female patient with a maternal history of PCT who presented clinical manifestations in adolescence, associated with triggers factors and excellent response to treatment with phlebotomies is reported (AU)

The porphyrias: pathophysiology.

Porphyrias are a group of inherited and acquired metabolic disorders due to a defect in haem biosynthesis. An enzymatic defect at different steps of haem synthesis leads to tissue accumulation and excessive excretion of porphyrins and/or their toxic precursors. The specific patterns of accumulation determine the variety of clinical manifestations, ranging from acute neurovisceral attacks to skin lesions and liver disease. Most enzyme defects represent partial deficiencies, while familial cases are linked to autosomal or recessive traits. The incomplete penetrance of the genetic defects often requires the triggering or aggravating effect of host-related or environmental factors. While genetics has a role in confirming clinical suspicion and in family screening, biochemical and clinical studies are still central in the diagnosis.

Longitudinal study of a mouse model of familial porphyria cutanea tarda.

Most rodent models of porphyria cutanea tarda (PCT) share in common the administration of iron and agents that induce transcription of cytochrome P450s. Dissection of changes related to porphyrin accumulation required generation of a genetic model free from exogenous precipitants. Mice heterozygous for a null Urod mutation and homozygous for null Hfe alleles spontaneously develop major increases in hepatic and urinary porphyrins several months after weaning but the high % uroporphyrin signature of PCT is established earlier, before total hepatic and urinary porphyrins rise. Total porphyrin levels eventually plateau at higher levels in females than in males. Porphyrinogens were the dominant tetrapyrroles accumulating in hepatocytes. Hepatic Urod activity is markedly reduced but total hepatic heme content does not diminish. Microsomal heme, however, is reduced and in vitro metabolism of prototype substrates showed that some but not all cytochrome P450 activities are reduced. High hepatic levels of uroporphyrinogen are also associated with increased glutathione S-transferase activity and elevated mRNA of 2 transporters, Abcc1 and Abcc4. This murine model of familial PCT affords the opportunity to study changes in porphyrinogen and porphyrin accumulation and transport in the absence of exogenous factors that alter P450 activity and transmembrane transporters.

Molecular heterogeneity of familial porphyria cutanea tarda in Spain: characterization of 10 novel mutations in the UROD gene.

BACKGROUND: Porphyria cutanea tarda (PCT) results from decreased hepatic uroporphyrinogen decarboxylase (UROD) activity. In the majority of patients, the disease is sporadic (S-PCT or type I) and the enzyme deficiency is limited to the liver. Familial PCT (F-PCT or type II) is observed in 20-30% of patients in whom mutations on one allele of the UROD gene reduce UROD activity by approximately 50% in all tissues. Another variant of PCT (type III) is characterized by family history of the disease although it is biochemically indistinguishable from S-PCT. OBJECTIVES: To investigate the molecular basis of PCT in Spain and to compare enzymatic and molecular analysis for the identification of patients with F-PCT. METHODS: Erythrocyte UROD activity measurement and mutation analysis of the UROD gene were carried out in a cohort of 61 unrelated Spanish patients with PCT and 50 control individuals. Furthermore, each novel missense mutation identified was characterized by prokaryotic expression studies. RESULTS: Of these 61 patients, 40 (66%) were classified as having S-PCT, 16 (26%) as having F-PCT and five (8%) as having type III PCT. Discordant results between enzymatic and molecular analysis were observed in two patients with F-PCT. In total, 14 distinct mutations were found, including 10 novel mutations: five missense, one nonsense, three deletions and an insertion. Prokaryotic expression of the novel missense mutations demonstrated that each results in decreased enzyme activity or stability. CONCLUSIONS: These results confirm the high degree of molecular heterogeneity of F-PCT in Spain and emphasize the usefulness of molecular genetic analysis to distinguish between F-PCT and S-PCT.

Porphyria cutanea tarda.

Porphyria cutanea tarda is the most common type of porphyria and results from low levels of the enzyme responsible for the fifth step in heme production.

Porphyria cutanea tarda in a patient with HIV-infection.

Several recent reports have described porphyria cutanea tarda (PCT) occurring in patients with HIV infection. Current evidence suggests that HIV infection may impair the hepatic cytochrome oxidase system, which could lead to an aberration in porphyrin metabolism and subsequently cause porphyria. We report a case of PCT in an HIV-infected patient who had multiple risk factors for this disorder.

Cytochrome p450A1 polymorphisms in a Caucasian population with porphyria cutanea tarda.

Porphyria cutanea tarda (PCT) is the most frequent porphyria in humans. The familial type is in contrast to the sporadic type due to an inherited defect of the uroporphyrinogen-II-decarboxylase (URO-D) and both types need additional porphyrinogens to lead to the clinical manifestation of the disease. Various factors such as xenobiotics (i.e. polycyclic aromatic hydrocarbons), alcohol, hormones and viral liver infections (hepatitis B and C) are known to induce porphyria. Cytochrome p450 enzymes play a crucial role in the metabolism of porphyrogens and therefore might have an important influence on the pathogenesis of hepatic porphyrias. Association of CYP1A2 polymorphisms with susceptibility to both types of PCT has already been described in Danish patients. We investigated 65 caucasian patients with PCT in comparison to a healthy control group concerning the tpe of PCT and the cytochrome p4501A1 polymorphisms (m1, m2 and m4) using polymerase chain reaction (PCR) and a restriction fragment length polymorphism. We found an increased incidence of the m4 polymorphism in the familial type of PCT (odds ratio 5.5, P-value 0.01), whereas the m1 and m2 mutations, might be provoked by a higher susceptibility to porphyrogens via the cytochrome p4501A1 m4 polymorphism.

Description of a new mutation in hepatoerythropoietic porphyria and prenatal exclusion of a homozygous fetus.

BACKGROUND: Hepatoerythropoietic porphyria (HEP) is usually a severe form of cutaneous porphyria, characterized biochemically by an increased urinary excretion of polycarboxylated porphyrins. The disease is the result of a profound deficiency (<10% of normal activity) of uroporphyrinogen decarboxylase (UROD) activity. Hepatoerythropoietic porphyria is inherited as an autosomal recessive trait, whereas familial porphyria cutanea tarda is dominant. At least 30 different mutations of the UROD gene have been identified in patients with HEP and familial porphyria cutanea tarda, with 1 predominant missense mutation (glycine-to-glutamic acid substitution at codon 281) in Spanish patients with HEP. OBSERVATION: A 5-year-old patient with first-degree-related parents presented with HEP and mild symptomatology. We found low levels of UROD enzymatic activity and a new homozygous mutation of the UROD gene, a phenylanine-to-leucine substitution at codon 46 (F46L). Both parents were healthy carriers of the mutation. The mother had reduced UROD activity (50% of normal), whereas the father had normal UROD activity. Prokaryotic expression of the F46L mutation using a pGEX vector has been used to confirm the deleterious effect of the mutation. When the mother started a new pregnancy, a prenatal study showed the absence of F46L mutation in the fetus and no accumulation of porphyrins in the amniotic fluid. CONCLUSIONS: A new mutation in the UROD gene causes a mild HEP phenotype. A normal UROD enzymatic activity was observed in the father, despite the presence of the heterozygous mutation. To our knowledge, this observation is the first description of a prenatal exclusion of HEP.

Porphyria cutanea tarda: multiplicity of risk factors including HFE mutations, hepatitis C, and inherited uroporphyrinogen decarboxylase deficiency.

The coexistence of factors considered to contribute to development of porphyria cutanea tarda was studied in 39 consecutive patients. Highly prevalent factors were alcohol intake in 79%, smoking in 86%, hepatitis C virus infection in 74%, estrogen use in 73% of 11 females, and at least one mutation in the HFE (hereditary hemochromatosis) gene in 65%. The C282Y mutation was found in 29%, H63D in 47%, and S65C in 0%. HFE genotypes included C282Y/C282Y in 9%, H63D/H63D in 9%, C282Y/H63D in 12%, C282Y/wild type in 9%, and H63D/wild type in 26%. Less prevalent were HIV infection in 15% (or 25% of those tested, N = 24) and erythrocyte uroporphyrinogen decarboxylase deficiency, which distinguishes familial (type 2) from "sporadic" (type 1) porphyria cutanea tarda, in 19%. Multiple contributing factors coexisted in both types 1 and 2, with 92% of all patients having three or more factors. These observations indicate that this porphyria is multifactorial in the individual patient, and therefore is seldom attributable to a single identifiable cause. Profiling for all potentially contributing factors is important for individualizing management.

Effective targeted gene 'knockdown' in zebrafish.

The sequencing of the zebrafish genome should be completed by the end of 2002. Direct assignment of function on the basis of this information would be facilitated by the development of a rapid, targeted 'knockdown' technology in this model vertebrate. We show here that antisense, morpholino-modified oligonucleotides (morpholinos) are effective and specific translational inhibitors in zebrafish. We generated phenocopies of mutations of the genes no tail (ref. 2), chordin (ref. 3), one-eyed-pinhead (ref. 4), nacre (ref. 5) and sparse (ref. 6), removing gene function from maternal through post-segmentation and organogenesis developmental stages. We blocked expression from a ubiquitous green fluorescent protein (GFP) transgene, showing that, unlike tissue-restricted limitations found with RNA-based interference in the nematode, all zebrafish cells readily respond to this technique. We also developed also morpholino-based zebrafish models of human disease. Morpholinos targeted to the uroporphyrinogen decarboxylase gene result in embryos with hepatoerythropoietic porphyria. We also used morpholinos for the determination of new gene functions. We showed that embryos with reduced sonic hedgehog (ref. 9) signalling and reduced tiggy-winkle hedgehog (ref. 10) function exhibit partial cyclopia and other specific midline abnormalities, providing a zebrafish genetic model for the common human disorder holoprosencephaly. Conserved vertebrate processes and diseases are now amenable to a systematic, in vivo, reverse-genetic paradigm using zebrafish embryos.

Mutations in familial porphyria cutanea tarda: two novel and two previously described for hepatoerythropoietic porphyria.

Uroporphyrinogen decarboxylase (URO-D) deficiency is responsible for two forms of genetic cutaneous porphyria: familial porphyria cutanea tarda (f-PCT) and hepatoerythropoietic porphyria (HEP). The f-PCT transmitted as an autosomal dominant trait, is characterized by photosensitive cutaneous lesions frequently associated to hepatic dysfunction and is precipitated by various ecogenic factors. The HEP, transmitted as a recessive trait, is more severe than f-PCT and would be considered as the homozygous form of f-PCT. For the mutational analysis of f-PCT patients, the entire URO-D gene was amplified and each exon, intron-exon boundaries and the promoter region were cycle sequenced. Five mutations were found in 6 unrelated families studied, of these, two were new: a nonsense mutation in exon 6 (W159X) and a splice defect in intron 9 (IVS9(-1)G-->C). The other two missense mutations, P62L and A80G, had been previously reported in the homozygous state in HEP families. The g10insA, reported in our laboratory, was again identified in other two unrelated families. In addition 3 novel URO-D polymorphisms in non-coding regions were found. The reverse transcription-PCR and sequencing of the splice mutation carrier's RNA did not reveal the presence of an abnormal mRNA, suggesting that no stable transcript from the mutated allele is synthesized. These results increase to 39 the number of mutations identified in the URO-D gene; 4 of them causing both HEP and f-PCT.

Porphyrin biosynthesis intermediates are not regulating delta-aminolevulinic acid transport in Saccharomyces cerevisiae.

In Saccharomyces cerevisiae, as in all eukaryotic organisms, delta-aminolevulinic acid (ALA) is a precursor of porphyrin biosynthesis, a very finely regulated pathway. ALA enters yeast cells through the gamma-aminobutyric acid (GABA) permease Uga4. The incorporation of a metabolite into the cells may be a limiting step for its intracellular metabolization. To determine the relationship between ALA transport and ALA metabolization, ALA incorporation was measured in yeast mutant strains deficient in the delta-aminolevulinic acid-synthase, uroporphyrinogen III decarboxylase, and ferrochelatase, three enzymes involved in porphyrin biosynthesis. Results presented here showed that neither intracellular ALA nor uroporphyrin or protoporphyrin regulates ALA incorporation, indicating that ALA uptake and its subsequent metabolization are not related to each other. Thus a key metabolite as it is, ALA does not have a transport system regulated according to its role.

Haem biosynthesis and human porphyria cutanea tarda: effects of alcohol intake.

The review describes the structural and biochemical properties of the haem biosynthetic enzyme, uroporphyrinogen decarboxylase (UROD), which sequentially catalyzes the removal of the four carboxyl groups from the acetate side chains of octacarboxylic uroporphyrinogen to form coproporphyrinogen, and the possible biochemical mechanism of the genesis of porphyria cutanea tarda (PCT). The disease is caused when the activity of UROD is significantly reduced. PCT is a multifactorial disease where both inherent and environmental factors such as alcohol, estrogens, halogenated aromatic hydrocarbons and viral infection (mainly hepatitis C) are involved in biochemical and clinical expression. In PCT, hepatic iron plays a key role. Alcohol intake could induce mobilization of iron from protein-bound ferritin. PCT should be managed by avoidance of these toxins and removal of iron by vigorous phlebotomy. Such iron-reduction therapy would provide additional benefit for hepatitis C patients by interferon therapy.

Correction of uroporphyrinogen decarboxylase deficiency (hepatoerythropoietic porphyria) in Epstein-Barr virus-transformed B-cell lines by retrovirus-mediated gene transfer: fluorescence-based selection of transduced cells.

Hepatoerythropoietic porphyria (HEP) is an inherited metabolic disorder characterized by the accumulation of porphyrins resulting from a deficiency in uroporphyrinogen decarboxylase (UROD). This autosomal recessive disorder is severe, starting early in infancy with no specific treatment. Gene therapy would represent a great therapeutic improvement. Because hematopoietic cells are the target for somatic gene therapy in this porphyria, Epstein-Barr virus-transformed B-cell lines from patients with HEP provide a model system for the disease. Thus, retrovirus-mediated expression of UROD was used to restore enzymatic activity in B-cell lines from 3 HEP patients. The potential of gene therapy for the metabolic correction of the disease was demonstrated by a reduction of porphyrin accumulation to the normal level in deficient transduced cells. Mixed culture experiments demonstrated that there is no metabolic cross-correction of deficient cells by normal cells. However, the observation of cellular expansion in vitro and in vivo in immunodeficient mice suggested that genetically corrected cells have a competitive advantage. Finally, to facilitate future human gene therapy trials, we have developed a selection system based on the expression of the therapeutic gene. Genetically corrected cells are easily separated from deficient ones by the absence of fluorescence when illuminated under UV light.

Porfiria cutánea tarda esclerodermiforme: presentación de cuatro casos y revisión de la literatura / Sclerodermic porphyria cutanea tarda: report of 4 casis and a review of the literature

La porfiria cutánea tarda esclerodermiforme (PCTE) es una forma poco frecuente de la presentación de la porfiria cutánea tarda (PCT), representando el 18-33 por ciento de los casos. Se caracteriza por manifestarse con placas esclerodermiformes de aparición insidiosa y tardía en el curso de la enfermedad. El déficit de la actividad de la enzima uroporfirinógeno decarboxilasa (UPDC), lleva a la acumulación de metabolitos intermedios responsables de las manifestaciones clínicas y bioquímicas. Se presentan cuatro pacientes con PCTE estudiados en nuestro Servicio, en un período de cuatro años (1992-1996)

A zebrafish model for hepatoerythropoietic porphyria.

Defects in the enzymes involved in the haem biosynthetic pathway can lead to a group of human diseases known as the porphyrias. yquem (yqe(tp61)) is a zebrafish mutant with a photosensitive porphyria syndrome. Here we show that the porphyric phenotype is due to an inherited homozygous mutation in the gene encoding uroporphyrinogen decarboxylase (UROD); a homozygous deficiency of this enzyme causes hepatoerythropoietic porphyria (HEP) in humans. The zebrafish mutant represents the first genetically 'accurate' animal model of HEP, and should be useful for studying the pathogenesis of UROD deficiency and evaluating gene therapy vectors. We rescued the mutant phenotype by transient and germline expression of the wild-type allele.