Uroporphyrinogen Decarboxylase Activity Research Articles

PORPHYRIA CUTANEATARDA: A CASE REPORT

Porphyria cutaneatarda (PCT) is a rare disease of porphyrin metabolism, related to a deficiency of Uroporphyrinogen decarboxylase activity. Clinically, it manifests itself by a skin fragility in photo-exposed areas. The characteristic biochemical profile of PCT, with elevated levels of urinary and plasma porphyrins, establishes the diagnosis. Treatment is based on phlebotomy, hydroxychloroquine (100 to 200 mg twice weekly) and control of susceptibility factors. We report a case of porphyria cutaneatarda in a male coast guard by profession.

Porphyria Cutanea Tarda in a 54-Year-Old Patient with a History of Hepatitis C: A Case Report

Background Porphyria CutaneaTarda (PCT) is the most common type of porphyria and is caused by a decrease in the activity of the hepatic enzyme uroporphyrinogen decarboxylase. It is expressed in both a sporadic form and genetic form and typically presents with cutaneous manifestations described as skin blisters in sun exposed areas. Case A 54-year-old male presented complaining of bullous itchy lesions on his hands and upper extremities that were at different stages of healing. Lab results were consistent with porphyria including elevated serum total porphyrins. He was scheduled for phlebotomy every other week for six weeks, hydroxychloroquine, minimize any sun exposure and to completely stop smoking. Conclusion Widespread skin lesions associated with underlying liver disease is a characteristic presentation for PCT. Hepatitis C is an antecedent risk factor for PCT, but can now be treated with antiviral therapy with the expectation of attainment of a sustained virologic response. Improvements in arresting progressive liver disease in Hepatitis C patients may improve PCT symptoms, as well. Keywords: Porphyria CutaneaTarda; Hepatitis C; Acquired liver disease.

S2631 Porphyria Cutanea Tarda, Type 2, in a Man With a Novel UROD Mutation

Introduction: Porphyria cutanea tarda (PCT) is usually caused by acquired defects in uroporphyrinogen decarboxylase (UROD) activity in the liver. 20% of cases occur in patients who have a genetically determined partial decrease in UROD activity. We describe a case of a man with a novel UROD mutation causing PCT type 2. Case Description/Methods: A 77-year-old man was evaluated for 6 months of painful blistering over his dorsal hands, forearms and head [Fig 1a]. His medical history was notable for hypertension, melanoma, and stroke. He reported heavy alcohol and tobacco use. He had no family history of porphyria. He worked for years at a manufacturing facility, with exposure to various industrial chemicals. More recently, he had exposure to weed killers, carburetor cleaners, and wood varnish. Exam revealed tense bullae with milia and hyperpigmented macules on dorsal hands and forearms. Biopsies revealed a subepidermal blister containing a small number of neutrophils with fibrin and evidence of festooning of the vessels consistent with porphyria. Labs revealed AST 63 U/L, ALT 64 U/L, alkaline phosphatase 54 U/L, and total bilirubin 0.8 mg/dL. Iron profile was unremarkable, and antibodies against HIV and hepatitis A, B and C were negative. Total plasma porphyrins were elevated to 13.4 mcg/dL. Fractionated urine, stool and plasma porphyrin levels were obtained [Table 1]. Urinary uro- and hepta-carboxyl porphyrins were markedly elevated, consistent with PCT. The patient was advised to start hydroxychloroquine 100 mg 3 times weekly and to avoid alcohol, tobacco use and sun exposure. Genetic testing revealed a novel mutation of UROD gene (c.224 G >C; p. Arg 75 Pro) with red blood cell UROD activity decreased by 50%. He returned to clinic 3 and 7 months after the index visit. He had stopped alcohol use, but continued smoking cigarettes. His hands were improved [Fig 1b]. Repeat urinary porphyrins showed improvement [Table 1]. The mutation in UROD is predicted to have a major effect on protein structure and function [Fig 1c]. Discussion: Inherited partial deficiency in UROD is not sufficient to cause clinically manifest PCT. Other factors that increase oxidative stress are also required. This patient has a mutation in the UROD gene not heretofore described in PCT type 2, but that we show markedly affects the structure and activity of the protein product. Nonetheless, the patient did not develop clinically manifest PCT until age 77, emphasizing the importance of acquired factors in disease pathogenesis.Figure 1.: A. Dorsal right hand at presentation B. Dorsal right hand at 7 month follow-up C. Structure of URO-D showing the substrate (yellow) in the active site located at the C-terminal end of the beta-sheets (magenta) that form the core of the TIM-barrel structure. The location of arginine 75 (Arg 75) is shown in green. Arg 75 is the penultimate residue in one of the eight corresponding alpha-helices that surround the central core. Arg 75 forms two hydrogen bonds with glutamic acid 45 (Glu 45) of the preceding helix in the structure. This hydrogen bonding network supports the overall tertiary fold of the protein in this otherwise solvent-exposed region of the protein. The UROD mutation of the patient (Arg 75 Pro) disrupts the helix with premature termination and more importantly eliminates the hydrogen bonding network.Table 1-A.: Results of Selected Laboratory Studies.Table 1-B.: Results of Selected Laboratory Studies.

A first report of porphyria cutanea tarda successfully treated with glycyrrhizin.

Porphyria cutanea tarda (PCT) is a condition that affects liver and skin by reduction of hepatic uroporphyrinogen decarboxylase activity. It is characterized by blistering lesions, erosions and crusts on sun-exposed areas. We report a 51-year-old male presenting with recurrent episodes of bullae, erosions, and crust on his neck and dorsum of the hands for 3 months. Aspartate aminotransferase, alanine aminotransferase, gamma-glutamyl transferase, alkaline phosphatase, lactate dehydrogenase levels, as well as total plasma porphyrin and urinary uroporphyrin levels were elevated. Based on the clinical manifestations, the history and laboratory findings, a diagnosis of PCT was made. The cutaneous and biochemical abnormalities of the patient improved with therapy of glycyrrhizin.

A case of porphyria cutanea tarda in the setting of hepatitis C infection and tobacco usage

Porphyria cutanea tarda (PCT) is the most common type of porphyria, presenting in middle-aged patients with a photodistributed vesiculobullous eruption, milia, and scars. Porphyria cutanea tarda occurs in relation to inhibition of uroporphyrinogen decarboxylase, a key enzyme in the heme biosynthesis pathway. A number of genetic and acquired factors increase susceptibility to PCT by reducing uroporphyrinogen decarboxylase activity. A handful of other vesiculobullous conditions may mimic PCT both clinically and histologically; therefore, both skin biopsy and laboratory evaluation are helpful in confirming the diagnosis. We report a case of PCT in the setting of cigarette usage and untreated hepatitis C infection.

Porphyria cutanea tarda and hepatoerythropoietic porphyria: Identification of 19 novel uroporphyrinogen III decarboxylase mutations

Porphyria Cutanea Tarda (PCT) is a cutaneous porphyria that results from the hepatic inhibition of the heme biosynthetic enzyme uroporphyrinogen decarboxylase (UROD), and can occur either in the absence or presence of an inherited heterozygous UROD mutation (PCT subtypes 1 and 2, respectively). A heterozygous UROD mutation causes half-normal levels of UROD activity systemically, which is a susceptibility factor but is not sufficient alone to cause type 2 PCT. In both Types 1 and 2 PCT, the cutaneous manifestations are precipitated by additional factors that lead to generation of an inhibitor that more profoundly reduces hepatic UROD activity. PCT is an iron-related disorder, and many of its known susceptibility factors, which include infections (e.g. hepatitis C virus, HIV), high alcohol consumption, smoking, estrogens, and genetic traits (e.g. hemochromatosis mutations) can increase hepatic iron accumulation. Hepatoerythropoietic Porphyria (HEP) is a rare autosomal recessive disease that results from homozygosity or compound heterozygosity for UROD mutations and often causes infantile or childhood onset of both erythropoietic and cutaneous manifestations.During the 11-year period from 01/01/2007 through 12/31/2017, the Mount Sinai Porphyrias Diagnostic Laboratory provided molecular diagnostic testing for 387 unrelated patients with PCT and four unrelated patients with HEP. Of the 387 unrelated individuals tested for Type 2 PCT, 79 (20%) were heterozygous for UROD mutations. Among 26 family members of mutation-positive PCT patients, eight (31%) had the respective family mutation. Additionally, of the four unrelated HEP patients referred for UROD mutation analyses, all had homozygosity or compound heterozygosity for UROD mutations, and all eight asymptomatic family members were heterozygotes for UROD mutations. Of the UROD mutations identified, 19 were novel, including nine missense, two nonsense, one consensus splice-site, and seven insertions and deletions. These results expand the molecular heterogeneity of PCT and HEP by adding a total of 19 novel UROD mutations. Moreover, the results document the usefulness of molecular testing to confirm a genetic susceptibility trait in Type 2 PCT, confirm a diagnosis in HEP, and identify heterozygous family members.

Relapse of porphyria cutanea tarda after treatment with phlebotomy or 4-aminoquinoline antimalarials: a meta-analysis.

Porphyria cutanea tarda (PCT) is the most common human porphyria. It is caused by hepatic deficiency of uroporphyrinogen decarboxylase activity, which is acquired in the presence of multiple susceptibility factors. PCT presents clinically with cutaneous blistering photosensitivity and is readily treatable with either repeated phlebotomy or 4-aminoquinoline antimalarials. To perform a systematic review and meta-analysis to compare the effectiveness of these quite different treatment approaches, especially on relapse rates (RRs) after achieving remission. Published studies that included follow-up for at least 1year after treatment of PCT were included. The primary study outcome was PCT relapse. Pooled data are reported as the RRs per person-year of follow-up with 95% confidence intervals (CIs). Of 375 articles identified as pertaining to PCT treatment, 12 were eligible for analysis. Of these, five used high-dose 4-aminoquinoline regimens (two combined with phlebotomy and three without phlebotomy), five used low-dose 4-aminoquinoline regimens and three used phlebotomy. RRs during the year after treatment were similar for the high- and low-dose 4-aminoquinoline groups (35-36%) and lower in the phlebotomy group (20%). The pooled RRs with their 95% CIs were 8·6 (3·9-13·3) per 100 person-years in the high-dose 4-aminoquinoline group, 17·1 (8·9-25·3) per 100 person-years in the low-dose 4-aminoquinoline group and 5·1 (0·5-10·6) per 100 person-years in the phlebotomy group. Subgroup and sensitivity analyses showed similar results. Clinical or biochemical RRs ranged from 5 to 17 per 100 person-years after remission of PCT. Relapses were somewhat more frequent after remission with 4-aminoquinoline regimens than after remission following phlebotomy. Prospective studies are needed to define better how often relapses occur with these treatments after documenting both clinical and biochemical remission of PCT.

Sporadic Porphyria in a patient with stage II melanoma treated with interferon α.

Porphyria cutanea tarda (PCT) is the most common form of human porphyria, due to reduced activity of uroporphyrinogen decarboxylase (UROD). There are many factors which can trigger PCT such as viral infections, excessive alcohol intake, iron overload, hepatotoxic drugs and hepatic tumours. Drug induced PCT is well documented but PCT induced by interferon α has rarely been described and only in cases of Hepatitis C Virus (HCV) infection or haematological malignancies. Here, we report the first case of de novo PCT induced by adjuvant interferon α (IFNα) therapy in a patient with stage II melanoma.

The D519G Polymorphism of Glyceronephosphate O-Acyltransferase Is a Risk Factor for Familial Porphyria Cutanea Tarda.

Both familial and sporadic porphyria cutanea tarda (PCT) are iron dependent diseases. Symptoms of PCT resolve when iron stores are depleted by phlebotomy, and a sequence variant of HFE (C282Y, c.843G>A, rs1800562) that enhances iron aborption by reducing hepcidin expression is a risk factor for PCT. Recently, a polymorphic variant (D519G, c.1556A>G, rs11558492) of glyceronephosphate O-acyltransferase (GNPAT) was shown to be enriched in male patients with type I hereditary hemochromatosis (HFE C282Y homozygotes) who presented with a high iron phenotype, suggesting that GNPAT D519G, like HFE C282Y, is a modifier of iron homeostasis that favors iron absorption. To challenge this hypothesis, we investigated the frequency of GNPAT D519G in patients with both familial and sporadic PCT. Patients were screened for GNPAT D519G and allelic variants of HFE (both C282Y and H63D). Nucleotide sequencing of uroporphyrinogen decarboxylase (URO-D) identified mutant alleles. Patients with low erythrocyte URO-D activity or a damaging URO-D variant were classified as familial PCT (fPCT) and those with wild-type URO-D were classified as sporadic PCT (sPCT). GNPAT D519G was significantly enriched in the fPCT patient population (p = 0.0014) but not in the sPCT population (p = 0.4477). Both HFE C282Y and H63D (c.187C>G, rs1799945) were enriched in both PCT patient populations (p<0.0001) but showed no greater association with fPCT than with sPCT. Conclusion: GNPAT D519G is a risk factor for fPCT, but not for sPCT.

Hepatitis C virus-associated porphyria cutanea tarda: A case report

Porhyria cutanea tarda (PCT) is a rare, inherited or acquired disorder due to decreased activity or deficiency of uroporphyrinogen decarboxylase (UROD), one of the enzymes in the haem synthetic pathway. It is characterized by cutaneous manifestations such as erosions, blisters and bulae in the dorsum of the hand, forearm, elbows and knees; and painful indolent sores that heal with dyspigmented and scarring lesions. A 25 year old sales man presented with a 7 month history of recurrent blistering of the skin of the extremities- hands, elbows, knees and feet which occurred spontaneously or following trivial trauma. There was no family history of similar skin symptoms. Examination showed broken and fresh blisters of varying sizes with some healed lesions on the dorsum of the hands, over the elbow and knee joints, and toes. Serum ferritin was 360μ/L (40- 340 μ/L), urine uroporphyrinogen was positive (+++) and Hepatitis C antibodies screening was positive. Some improvement of the cutaneous lesion was noticed following commencement of therapeutic phlebotomy. Keywords: Porhyria, blisters, Hepatitis C virus, uroporphyrinogen

Porphyria Cutanea Tarda – a Case Report

Abstract Porphyria cutanea tarda is a metabolic disorder that results from a reduced enzymatic activity of uroporphyrinogen decarboxylase. It is the commonest chronic porphyria. Two types of this disease have been reported up to now: acquired (Type 1, 80%) and inherited (Type 2, 20%) an autosomal dominant pattern with low clinical penetrance. Both types are associated with haemochromatosis, alcohol abuse, estrogens, iron overload, hepatitis C virus infection, and halogenated aromatic hydrocarbons causing deficiency of the uroporphyrinogen decarboxylase enzyme in the liver. In this case report we described a 23-year-old woman with increased hair growth on the face and neck, who visited an outpatient dermatology clinic for laser hair removal due to excessive hair growth on the face and neck during the last eight years (Figures 1, 2). Four laser treatments were carried out with incomplete effects. After the fourth laser hair removal treatment, a small sore on the tip of the nose was observed. The patient used oral contraceptive pills during the past 8 months. No additional medications were taken. The diagnosis of porphyria cutanea tarda was confirmed by specific biochemical analyses, since increased excretion of uroporphyrin and coproporphyrin were detected. After discontinuation of drospirenone and ethinyl estradiol (YazÒ tablets) a gradual clinical and laboratory improvement was noticed suggesting a causative role of this drug. There are many published reports discussing and describing estrogens as contraceptive agents, hormone supplements for postmenopausal replacement therapy in females, and adjunctive hormonal therapy in males with prostatic carcinoma, being the probable trigger of porphyria cutanea tarda. However, the mechanisms by which estrogens exert their effects on disease expression have not yet been fully clarified. Conclusion: this case report points to the importance of hypertrichosis as the first manifestation of porphyria cutanea tarda, since it may be a long lasting sign before the onset of other clinical symptoms of the disese

Familial porphyria cutanea tarda in Spain: Characterization of eight novel mutations in the UROD gene and haplotype analysis of the common p.G281E mutation

Porphyria cutanea tarda (PCT) results from decreased activity of uroporphyrinogen decarboxylase (UROD) in the liver. Deficiency in this enzyme results in accumulation of highly carboxylated porphyrins responsible for the disease. PCT usually occurs in adulthood and is characterized by cutaneous photosensitivity, hyperpigmentation, skin fragility and hypertrichosis. Familial PCT (F-PCT) occurs in 20–30% of patients in whom UROD gene mutations in heterozygosity decrease the enzymatic activity to about 50% in all tissues. The rare homozygous form of F-PCT (hepatoerythropoietic porphyria) has more severe clinical features and onset in childhood. In Spain, F-PCT is molecularly heterogeneous and the most frequent UROD mutation is p.G281E. In the present study, we searched for the molecular defect causing F-PCT in a group of Spanish patients and investigated whether the p.G281E mutation in the Spanish population came from a single or various origins. Among seventeen F-PCT patients, sixteen UROD mutations were identified, including eight novel ones: six missense (p.A23V, p.L78P, p.W180G, p.T196I, p.E278G and p.V279M), one frameshift (c.233delT) and one splice site mutation (c.774G>C). Prokaryotic expression studies showed the detrimental effect for each missense mutation, whereas reverse transcription-PCR and sequencing demonstrated that the novel splice site mutation caused exon 7 skipping. Moreover, haplotype analysis performed in Spanish families with the p.G281E mutation indicated that this lesion is associated with at least five haplotype backgrounds. These results extend knowledge on the molecular heterogeneity of F-PCT and suggest multiple origins of the p.G281E mutation.

Is Hydroxychloroquine As Effective As Phlebotomy for Porphyria Cutanea Tarda

Porphyria cutanea tarda (PCT) is an iron-related disorder that results from reduced activity of hepatic uroporphyrinogen decarboxylase. Treatment

Low-Dose Hydroxychloroquine Is as Effective as Phlebotomy in Treatment of Patients With Porphyria Cutanea Tarda

Porphyria cutanea tarda (PCT) is an iron-related disorder caused by reduced activity of hepatic uroporphyrinogen decarboxylase; it can be treated by phlebotomy or low doses of hydroxychloroquine. We performed a prospective pilot study to compare the efficacy and safety of these therapies. We analyzed data from 48 consecutive patients with well-documented PCT to characterize susceptibility factors; patients were treated with phlebotomy (450 mL, every 2 weeks until they had serum ferritin levels of 20 ng/mL) or low-dose hydroxychloroquine (100 mg orally, twice weekly, until at least 1 month after they had normal plasma levels of porphyrin). We compared the time required to achieve a normal plasma porphyrin concentration (remission, the primary outcome) for 17 patients treated with phlebotomy and 13 treated with hydroxychloroquine. The time to remission was a median 6.9 months for patients who received phlebotomy and 6.1 months for patients treated with hydroxychloroquine treatment (6.7 and 6.5 mo for randomized patients), a difference that was not significant (log-rank, P = .06 and P = .95, respectively). The sample size was insufficient to confirm noninferiority of hydroxychloroquine treatment (hazard ratio, 2.19; 95% confidence interval, 0.95-5.06) for all patients. Patients who received hydroxychloroquine had substantially better compliance. There were no significant side effects of either treatment. Hydroxychloroquine, 100 mg twice weekly, is as effective and safe as phlebotomy in patients with PCT, although noninferiority was not established. Given these results, higher-dose regimens of hydroxychloroquine, which have more side effects, do not seem justified. Compliance was better and projected costs were lower for hydroxychloroquine than phlebotomy treatment. Long-term studies are needed to compare durability of response. ClinicalTrials.gov number, NCT01573754.

Molecular analysis of the UROD gene in 17 Argentinean patients with familial porphyria cutanea tarda: Characterization of four novel mutations

Porphyria cutanea tarda (PCT) is caused by decreased activity of uroporphyrinogen decarboxylase (UROD) in the liver. The disease usually occurs in adulthood and is characterized by cutaneous photosensitivity, hyperpigmentation, skin fragility and hypertrichosis, due to the accumulation of porphyrins produced by oxidation of uroporphyrinogen and other highly carboxylated porphyrinogens overproduced as a result of the enzyme deficiency. PCT is generally sporadic, but about 20–30% of patients have familial-PCT (F-PCT) which is associated with heterozygosity of mutations in the UROD gene. In the present study we have found the molecular defect in seventeen unrelated Argentinean patients with F-PCT, identifying a total of eleven UROD gene mutations: four novel and seven previously described. The novel mutations were: a guanine insertion at the 5′ splice junction of intron 2, a three nucleotide deletion causing the lost of valine 90, a deletion of 22bp in exon 6 and a deletion of part of the polyadenylation signal. Prokaryotic expression studies showed that the novel amino acid deletion resulted in an inactive protein. Mutations c.10insA and p.M165R, previously found in Argentinean patients, were recurrent in this study; they are the most frequent in Argentina accounting for 40% of the mutant alleles characterized to date.

Comprehensive cytochrome P450 CYP1A2 gene analysis in French caucasian patients with familial and sporadic porphyria cutanea tarda

Porphyria cutanea tarda (PCT), the most frequent type of porphyria, results from decreased uroporphyrinogen decarboxylase (UROD) activity. Two forms of PCT have been described: a familial form (fPCT) characterized by the inherited decrease of UROD activity in all tissues and a sporadic form (sPCT) characterized by decreased UROD activity in the liver. Cytochrome P450 CYP1A2 plays a major role in triggering experimental uroporphyria in rodents. It has been suggested that the highly inducible -163A/A genotype of the CYP1A2 gene could confer a heightened risk of PCT in patients. To examine the impact of CYP1A2 polymorphisms on the clinical course of PCT. We performed an extensive CYP1A2 gene analysis in 96 (48 fPCT and 48 sPCT) unrelated French caucasian patients with PCT and in 99 healthy volunteers of similar ethnic origin. Results We did not observe any difference in CYP1A2 allele distribution, including a novel and rare CYP1A2 c.1063C>T (p.R355W) single nucleotide polymorphism. In addition, we compared the frequency of the -163A highly inducible allele both in patients with symptomatic fPCT (n = 48) and in asymptomatic UROD gene mutations carrier relatives (n=54). This variant was not over-represented in patients with PCT vs. either healthy volunteers or asymptomatic UROD gene mutation carriers. The CYP1A2 genotype does not appear to be a major susceptibility factor in the development of fPCT or sPCT in the French population.

Liver Cirrhosis Induced by Porphyria Cutanea Tarda: A Case Report and Review

Porphyria cutanea tarda (PCT) is a metabolic disorder that results in a decrease in uroporphyrinogen decarboxylase activity. It is characterized by photosensitivity, bullae formation, and skin pigmentation. There are four types of PCT: acquired, familial, toxic, and hepatoerythropoietic. Uroporphyrin levels are elevated in the urine of PCT patients. PCT can be differentiated from other porphyrias by its clinical characteristics and the porphyrin levels in the serum, erythrocytes, urine, and feces. This metabolic disorder can lead to liver dysfunction as well as histological changes such as fatty infiltration or hepatic fibrosis. PCT rarely manifests as liver cirrhosis. We report herein a case of PCT-induced liver cirrhosis that progressed to hepatic failure.

Cellular Distribution of Porphyrins In Porphyria Cutanea Tarda

AbstractAbstract 165Porphyria cutanea tarda (PCT), the most common porphyria in humans, results from subnormal activity of uroporphyrinogen decarboxylase (URO-D) in hepatocytes. The enzymatic defects results in cellular accumulation of the highly carboxylated uroporphyrinogen and heptacarboxyl porphyrinogen. The excess porphyrinogens are oxidized to porphyrins, exported to plasma and eventually eliminated in the urine. The mechanism by which uroporphyrin and heptacarboxyl porphyrin are transported across cellular membranes is not known. We generated a mouse model of the familial form of PCT 1. Mice heterozygous for a deletion of the Uro-d gene and homozygous for deletion of the hemochromatosis gene Hfe (genotype Uro-d+/−;Hfe−/−) accumulate hepatic porphyrins in a pattern similar to humans with PCT. Hepatocytes were isolated from porphyric mice using an in situ two-step EGTA/collagenase perfusion followed by an iso-density Percoll centrifugation step to remove damaged cells. Confocal microscopy was used to examine cells for porphyrin fluorescence by illuminating cells at 405 nm and monitoring the emission between 600 and 650 nm. Fluorescent porphyrins were present as punctate bodies within the cytosol of the hepatocytes. Co-staining with fluorescent probes (mitotracker and lysotracker) demonstrated co-localization of porphyrins with lysotracker, indicating that porphyrins were present in lysosomes. We utilized a yeast model to determine the molecular mechanism by which porphyrins are transferred from the cytosol to the lysosome. In S. cerevisiae the vacuole is analogous to the mammalian lysosome. The yeast homolog of Uro-d is HEM12. In a hem12 deletion strain, uroporphyrin accumulates in the vacuole. ABC transporters have previously been shown to transport tetrapyrroles across membranes. We used a candidate approach to identify the ABC transporter responsible for vacuolar transport of uroporphyrin by creating deletion strains of the five known vacuolar ABC transporters BPT1, YBT1, YCF1, VMR1 and NFT1. Vacuolar membranes were prepared from these strains by spheroplasting yeast with oxalyticase, osmotically lysing the cells and floating the vacuoles on a Ficoll gradient. Isolated vacuoles were assayed for tetrapyrrole uptake by incubating vacuoles (200 ug total protein), substrate (20 uM) and Mg2+-ATP (50 uM) at 30 °C for 1, 2, 4 and 8 min in 100 uL of import buffer (300 mM sorbitol, pH 6.8). As controls, reactions were carried out at 4 °C and in the absence of ATP. Vacuolar import of uroporphyrin was temperature-dependent (no import occurred at 4 °C) and was dependent on the presence of ATP. Uroporphyrinogen was imported but, the rate was approximately 10% that of uroporphyrin. No import of protoporphyrin IX was observed. Import of uroporphyrin into vacuoles from each of the ABC transporter mutants was essentially the same as wild-type vacuoles with the exception of the ycf1 deletion strain. There was no import of uroporphyrin or uroporphyrinogen in vacuoles from the ycf1 deletion stain. The mammalian ABC-type transporter with the highest homology to yeast YCF1 is ABCC1. ABCC1 has recently been shown to transport a tetrapyrrole (cobalamin) 2 making ABCC1 a candidate transporter responsible for moving uroporphyrin across cellular membranes in humans.1. Phillips JD, Jackson LK, Bunting M, et al. A mouse model of familial porphyria cutanea tarda. Proc Natl Acad Sci U S A. 2001;98:259-264.2. Beedholm-Ebsen R, van de Wetering K, Hardlei T, Nexo E, Borst P, Moestrup SK. Identification of multidrug resistance protein 1 (MRP1/ABCC1) as a molecular gate for cellular export of cobalamin. Blood. 2010;115:1632-1639. Disclosures:No relevant conflicts of interest to declare.

CYP1A2*1F and GSTM1 Alleles Are Associated with Susceptibility to Porphyria Cutanea Tarda

Porphyria cutanea tarda (PCT) is a cutaneous porphyria with sporadic (type 1) and familial (type 2) subtypes, both resulting from decreased hepatic uroporphyrinogen decarboxylase (UROD) activity. Environmental and genetic factors are involved in the development of PCT, and genetic variants in the cytochrome P450 (CYP ) genes, CYP1A1 and CYP1A2, have been implicated. We investigated the association between PCT and variants in CYP1A1, CYP1A2 and CYP2E1, and the glutathione-S-transferase (GST ) genes, GSTM1 and GSTT1. PCT diagnosis was based on urinary or plasma porphyrin profiles. Patients were classified as type 1 or 2 PCT based on UROD mutation analysis. The CYP1A2*1F promoter A allele frequency was significantly higher (P < 0.022) and the A/A genotype frequency marginally higher in PCT patients overall (P < 0.057), with the A/A genotype significantly more common in type 1 PCT (P < 0.043). The presence of the wild-type GSTM1 allele also was associated significantly with PCT (P < 0.019). Neither hemochromatosis (HFE) mutations, tobacco smoking, hepatitis C and HIV infection, ethanol consumption, nor estrogen use were associated with these allelic variants. Age at onset was significantly lower in type 2 PCT patients (P < 0.001), as observed previously. Thus, positive associations between PCT and the CYP1A2*1F promoter A allele and A/A genotype and the wild-type GSTM1 allele indicates that these functional hepatic biotransformation enzymes are risk factors for the development of this disease.

Porphyria cutanea tarda – When skin meets liver

Porphyria cutanea tarda (PCT) is the most frequent type of porphyria worldwide and results from a catalytic deficiency of uroporphyrinogen decarboxylase (UROD), the fifth enzyme in heme biosynthesis. At least two different types of PCT are currently distinguished: an acquired variant, also referred to as sporadic or type I PCT, in which the enzymatic deficiency is limited to the liver; and an autosomal dominantly inherited form, also known as familial or type II PCT, in which there is a decrease of enzymatic activity in all tissues. The cutaneous findings include increased photosensitivity, skin fragility, blistering, erosions, crusts, and miliae on the sun-exposed areas of the body. Additionally, hyperpigmentation, hypertrichosis, sclerodermoid plaques, and scarring alopecia might be observed. In patients with type I PCT, there is a significant association with liver disease that can be triggered by genetic and environmental factors, such as alcohol abuse, iron overload, haemochromatosis, polychlorinated hydrocarbons, and hepatitis C virus infection. The diagnosis of PCT can be made based on the skin symptoms, a characteristic urinary porphyrin excretion profile, and the detection of isocoproporphyrin in the feces. In red blood cells of individuals with type II PCT, UROD activity is decreased by approximately 50% due to heterozygous mutations in the UROD gene. Here we provide an update on clinical, diagnostic and therapeutic aspects of PCT, a disorder that affects both skin and liver.