Urinary Coproporphyrin Research Articles

Urinary Elimination of Coproporphyrins Is Dependent onABCC2 Polymorphisms and Represents a Potential Biomarker of MRP2 Activity in Humans

MRP2 encoded by ABCC2 gene is involved in the secretion of numerous drugs and endogenous substrates. Patients with Dubin-Johnson syndrome due to mutation in ABCC2 gene have elevated urinary coproporphyrin ratio (UCP I/(I + III)). Here we investigated whether this ratio could serve as a biomarker of MRP2 function. Phenotype-genotype relationships were studied in 74 healthy subjects by measuring individual UCP I/(I + III) ratio obtained on 24-hour urine and by analyzing five common SNPs in ABCC2 gene. The UCP I/(I + III) ratio varied from 14.7% to 46.0% in our population. Subjects with 3972TT genotype had a higher ratio (P = .04) than those carrying the C allele. This higher UCP I/(I + III) ratio was correlated with a higher level of isomer I excretion. This study provides a proof of concept that UCP I/(I + III) ratio can be used as a biomarker of MRP2 function in clinical studies as it provides quantitative information about the in vivo activity of MRP2 in a given patient.

Hyperbilirubinemia syndromes (Gilbert-Meulengracht, Crigler-Najjar, Dubin-Johnson, and Rotor syndrome)

Hyperbilirubinemia is an important clinical sign that often indicates severe hepatobiliary disease of different etiologies. Inherited non-haemolytichyperbilirubinemic conditions include Dubin-Johnson, Rotor, and Gilbert-Meulengracht syndromes, which are important differential diagnoses indicating benign disease that require no immediate treatment. Dubin-Johnson and Rotor syndromes are rare, exhibit mixed direct and indirect hyperbilirubinemia as well as typical profiles or urinary coproporphyrin excretion. Gilbert-Meulengracht disease leads to unconjugated hyperbilirubinemia because of impaired glucuronidation activity, and is part of a spectrum of genetic variants also encompassing fatal Crigler-Najjar syndrome. Gilbert-Meulengracht syndrome can be diagnosed by clinical presentation, biochemistry and genotyping, and carries significance regarding the disposition towards drug-associated toxicity. In addition, the precise diagnosis of these inherited hyperbilirubinemic syndromes avoids unnecessary invasive procedures for suspected more severe hepatobiliary disease.

A novel, selective, and rapid fluorimetric method for the simultaneous analysis of coproporphyrin and uroporphyrin in urine

A simple and rapid spectrofluorimetric method is described for the determination of the closely overlapping mixture of coproporphyrin (CP) and uroporphyrin (UP) in urine samples. Matrix Isopotential Synchronous Fluorescence Spectrometry (MISFS) was applied to improve the spectral resolution for the severely overlapped spectra of the urinary porphyrins. First-order derivative technique eliminates the background interference of each component on the other. Using these two techniques together, selectivity was improved, while maintaining a high sensitivity, and time-consuming separation processes and multiple scanning processes were avoided. The limits of detection were 0.15 nmol L −1 and 0.1 nmol L −1 for CP and UP, respectively. The concentrations of CP and UP were determined from the peak amplitudes of the Derivative Matrix Isopotential Synchronous Fluorescence (DMISF) spectra, at their detection points where the interference was suppressed. Porphyrins excretion in urine samples, collected from normal subjects, was studied. A comparison between the new method and the anion-exchange chromatographic method of Martinez and Mills was established using Bland–Altman method and the results indicate that these two methods are in a good agreement with each other.

Quantification of coproporphyrin isomers I and III in urine by HPLC and determination of their ratio for investigations of Multidrug Resistance Protein 2 (MRP2) function in humans

We describe here the development of a high-performance liquid chromatography (HPLC) method for quantitative determination of the ratio of isomers I and III of urinary coproporphyrin [the UCP I/(I + III) ratio], which is used for the diagnosis of Dubin–Johnson syndrome (DJS). This technique could also be used for research applications, such as investigations of the function of Multidrug Resistance Protein 2 (MRP2) in humans. Chromatographic separation was achieved on a reverse-phase C18 Symmetry ® column (5 μm; 4.8 mm × 250 mm), using a mobile phase consisting of a mixture of acetonitrile and acetate buffer (0.015 M, pH 4), with fluorescence detection based on excitation at 365 nm and emission at 624 nm. The method was validated over a concentration range of 10–400 nmol/l for UCP I and 30–560 nmol/l for UCP III, yielding calibration curves with correlation coefficients greater than 0.998. The lower limit of quantification (LLOQ) was 7 nmol/l for UCP I and 10 nmol/l for UCP III. Inter- and intra-day precision (CV < 5%) and accuracy (95–99%) complied with ICH guidelines. We also demonstrated that samples could be stored for 3 days at +4 °C and for 12 months at −20 °C with no change in UCP ratio (CV < 5%), providing a basis for storage recommendations for future clinical studies based on this analysis. Our method is simple, rapid and universal and is suitable for quantitative determinations of each isomer and their ratio for routine and research purposes.

On‐line capillary electrophoresis‐electrospray ionization mass spectrometry analysis of urinary porphyrins

A rapid, high-resolution and high-efficiency novel method for the simultaneous determination of mesoporphyrin (MP), coproporphyrin (CP) and uroporphyrin (UP) in human urine by capillary electrophoresis coupled with electrospray ionization mass spectrometry (CE-ESI-MS) was developed. The simple laboratory-made interface was developed by using a micro-tee connection and a liquid junction. The porphyrins were well separated by CE with a positive 12 kV voltage in a 20 mM ammonium acetate buffer (pH 10.5) containing 40% v/v acetonitrile. The sheath liquid was composed of acetonitrile-water (50:50 v/v) containing 5 mM ammonium acetate and 0.1% v/v formic acid (pH 3.0) with a flow rate of 5 microL/min. The porphyrins were identified with the criteria of migration time and m/z values, and quantified with the measurement of peak area of [M+H]+ ion. Limits of detection for MP, CP and UP were 85 nM, 140 nM and 300 nM, respectively. The correlation coefficients of calibration curves were between 0.9956 and 0.9862. The intra-day precisions in terms of relative standard deviations (n = 12) of the method were 1.1-3.9% for migration times and 2.3-14.1% for peak areas. The porphyrin recoveries of spiked urine samples were between 73% and 96%. The liquid junction interface for CE-ESI-MS was demonstrated to be applicable for the potential quantitative analysis of clinical samples.

Hexachlorobenzene Treatment on Hepatic Mitochondrial Function Parameters and Intracellular Coproporphyrinogen Oxidase Location

These studies try to elucidate why isocoproporphyrin appears in hexachlorobenzene-poisoned rats' feces. Chronic exposure of hexachlorobenzene to rats produces an experimental model for human porphyria cutanea tarda. After 8 weeks of treatment, rats showed high porphyrin excreta and 50% inhibition of liver uroporphyrinogen decarboxylase activity. Uroporphyrin plus heptacarboxylic porphyrin exceeded coproporphyrin in urine, whereas in feces, isocoproporphyrin, from abnormal pentacarboxylic porphyrinogen III oxidative decarboxylation by liver coproporphyrinogen oxidase, became the main porphyrin. Trypsin-treated mitochondria showed that the outer and inner membrane permeability barrier was highly conserved after hexachlorobenzene intoxication. In digitonin-treated hexachlorobenzene mitochondria, coproporphyrinogen oxidase was free in the mitochondrial intermembrane space, whereas in normal mitochondria, 30% to 50% remained anchored to the inner membrane. Hexachlorobenzene led to a decrease in respiratory control and ADP/O ratios (uncoupled mitochondria). Albumin restored oxidative phosphorylation, indicating no irreversible inner membrane damage. Normal and hexachlorobenzene mitochondria oscillatory studies exhibited similar damping factor values, showing that hexachlorobenzene had no significant effect on membrane fluidity and elasticity. Mitochondrial uncoupling could explain the free state of the enzyme within the intermembrane space. The free state of the enzyme makes it more flexible and would allow pentacarboxylic porphyrinogen III, whose levels are increased, to compete with coproporphyrinogen III and being transformed into dehydroisocoproporphyrinogen, the liver forerunner of fecal isocoproporphyrin.

A Prospective Study of Mercury Toxicity Biomarkers in Autistic Spectrum Disorders*

Porphyrins are derivatives formed in the heme synthesis pathway and porphyrins afford a measure of xenobiotic exposure. The steps in the heme pathway most vulnerable to heavy metal inhibition are uroporphyrin decarboxylase (UROD) and coproporphyrinogen oxidase (CPOX) reactions. Mercury toxicity was associated with elevations in urinary coproporphyrin (cP), pentacarboxyporphyrin (5cxP), and precoproporphyrin (prcP) (also known as keto-isocoproporphyrin) levels. Two cohorts of autistic patients in the United States and France had urine porphyrin levels associated with mercury toxicity. A prospective study of urinary porphyrin testing at LabCorp (United States) and the Laboratoire Philippe Auguste (France) involving 71 autism spectrum disorder (ASD) patients, neurotypical sibling controls, and general population controls was undertaken. ASD patients had significant elevations in urinary levels of cP, 5cxP, and prcP relative to controls, and > 50% of ASD patients had urinary cP levels more than 2 standard deviations above the mean values for neurotypical sibling controls. Significant reductions in urinary 5cxP and cP levels were observed in ASD patients following chelation. A significant correlation was found between urinary porphyrins measured at LabCorp and those measured at the Laboratoire Philippe Auguste on individual ASD patients. The established developmental neurotoxicity attributed to mercury and biochemical/genomic evidence for mercury susceptibility/toxicity in ASDs indicates a causal role for mercury. Urinary porphyrin testing is clinically available, relatively inexpensive, and noninvasive. Porphyrins need to be routinely measured in ASDs to establish if mercury toxicity is a causative factor and to evaluate the effectiveness of chelation therapy.

Urinary arsenic methylation and porphyrin profile of C57Bl/6J mice chronically exposed to sodium arsenate

Arsenic interferes with the function of enzymes responsible for haem biosynthesis leading to alteration in the porphyrin profile. In this study, young female C57Bl/6J mice were given drinking water containing 0, 100, 250 and 500 microg As(V)/L as sodium arsenate ad libitum for 24 months. 24 h pooled urine samples were collected bimonthly for urinary arsenic methylation and porphyrin analyses by HPLC-ICP-MS and HPLC respectively. The levels of total arsenic were significantly dose related except for the 2nd month interval. No significant differences in the urinary arsenic methylation pattern between control and test groups were observed. Coproporphyrin I (Copro I) showed a significant dose-response relationship after 12, 14 and 20 months of exposure. Significant differences in the levels of coproporphyrin III (Copro III) were observed in the 8th month in 250 and 500 microg/L treatment groups and the dose-response pattern was maintained after 10 and 12 months. Our results suggest that urinary arsenic is a useful biomarker for internal dose, and that urinary coproporphyrin can be used as an early warning biomarker of effects before the onset of cancer.

A mutation in the drug transporter gene ABCC2 associated with impaired methotrexate elimination

Human multidrug resistance protein 2 (MRP2, encoded by ABCC2) is involved in active efflux of anionic drugs such as methotrexate. MRP2 is expressed on the luminal side of hepatocytes and renal proximal tubular cells, indicating an important role in drug elimination. We postulated that loss-of-function mutations in ABCC2, which are involved in the Dubin-Johnson syndrome, may be associated with impaired methotrexate elimination and an increased risk of toxicity. We studied the biological phenotype and ABCC2 coding sequence in a patient receiving a high-dose methotrexate infusion for large B-cell lymphoma and who had an unusual pharmacokinetic profile, mainly characterized by a three-fold reduction in the methotrexate elimination rate. This resulted in severe methotrexate over-dosing and reversible nephrotoxicity. An inversion of the urinary coproporphyrin isomer I/III ratio (a specific biological marker of the Dubin-Johnson syndrome) was observed in this patient. Genetic analysis of ABCC2 identified a heterozygous mutation replacing a highly conserved arginine by glycine in the cytoplasmic part of the second membrane-spanning domain (position 412 of MRP2), a region associated with substrate affinity. This genetic variant was not found in a control population. Functional analysis in transiently transfected Chinese hamster ovary cells revealed a loss of transport activity of the G412 MRP2 mutant protein. An ABCC2 mutation altering MRP2-mediated methotrexate transport and resulting in impaired drug elimination and subsequent renal toxicity was identified. Candidates for methotrexate therapy should be considered for MRP2 functional testing.

Increased urinary coproporphyrin excretion observed in patients with differently staged Hodgkin's disease treated with chemotherapy

It has been reported that patients with Hodgkin's disease (HD) show altered porphyrin metabolism, and suggested that the cause is the neoplastic process itself. If this is true, disease progression should be associated with higher levels of porphyrin excretion. The aim of this study was to evaluate urinary coproporphyrin levels in patients with Hodgkin's disease at different stages. As many of the patients received chemotherapy, another aim was to verify experimentally whether chemotherapeutic agents might increase porphyrin levels in rabbits. All of the patients had above-normal urinary coproporphyrin levels. On the other hand, rabbits receiving the porphyrin precursor 5-aminolevulinic acid (5-ALA), and also treated with doxorubicin, showed very high plasma porphyrin levels. The increased levels of urinary coproporphyrins seem to be due to the disease itself, since the patients in stages III and IV had higher excretion values, presumably due to biochemical heme synthesis lesions that lead to the availability of the porphyrin precursor, as well as coproporphyrin accumulation and excretion. The altered porphyrin synthesis may be attributable to the cytotoxic oxygen species generated in the presence of NADH and iron. As the patients also received extensive chemotherapy regimes, the altered porphyrin metabolism may be affected by antineoplastic treatment generating oxygen reactive radicals. The alterations in porphyrin metabolism induced by chemotherapeutic agents appear to be demonstrated in rabbits in which doxorubicin increases porphyrin synthesis after porphyrin precursor treatment.

Urinary arsenic speciation and porphyrins in C57Bl/6J mice chronically exposed to low doses of sodium arsenate

Arsenic has been classified as a human carcinogen based on epidemiological data however the mechanism of its carcinogenicity is still unclear. Urinary biomarkers for chronic arsenic exposure would be valuable as an early warning indicator for timely interventions. In this study, young female C57Bl/6J mice were given drinking water containing 0, 100, 250 and 500 μg As v/L as sodium arsenate ad libitum for 12 months. Urine was collected bimonthly for urinary arsenic methylation assay and porphyrin analysis. All detectable arsenic species showed strong linear correlation with administered dosage and the arsenic methylation patterns were similar in all three treatment groups. No significant changes of methylation patterns were observed over time for either the control or test groups. Urinary coproporphyrin III was significantly increased in the 8th month in 250 and 500 μg/L groups and remained significantly dose-related after 10 and 12 months. Coproporphyrin I also showed a significant dose-response relationship after 12 months. Our results confirm that urinary arsenic is a useful biomarker for internal dose. The alteration of porphyrin profile suggests that arsenic can affect the heme metabolism and this may occur prior to the onset of arsenic induced carcinogenesis.

Increased excretion of urine coproporphyrins during daunorubicin administration in patients affected by acute myelogenous leukemia

Increased erythrocyte porphyrin values and high urine porphyrin levels have been reported in leukemic patients, but it is not clear whether the alteration in porphyrin metabolism is due to the leukemia or its treatment. The aim of this study was to compare porphyrin levels in leukemic patients undergoing chemotherapy or not. We analysed porphyrin values in patients with acute emyelogenous leukemia, who had or had not received chemotherapy according to Gale. Erythrocyte and urine porphyrin levels were increased as a result of the leukemic process, but urine coproporphyrins were further increased by daunorubicin treatment. These higher urine coproporphyrin levels were attributed to the activity of daunorubicin, which is known to interfere with the coproporphyrinogen decarboxylation process leading to the accumulation and high excretion of coproporphyrins in urine.

Acute Porphyrias: A Case Report and Review

Acute Porphyrias: A Case Report and Review

Clinical and biochemical characteristics and genotype-phenotype correlation in Finnish variegate porphyria patients.

Variegate porphyria (VP) is an inherited metabolic disease resulting from the partial deficiency of protoporphyrinogen oxidase, the penultimate enzyme in the heme biosynthetic pathway. We have evaluated the clinical and biochemical outcome of 103 Finnish VP patients diagnosed between 1966 and 2001. Fifty-two per cent of patients had experienced clinical symptoms: 40% had photosensitivity, 27% acute attacks and 14% both manifestations. The proportion of patients with acute attacks has decreased dramatically from 38 to 14% in patients diagnosed before and after 1980, whereas the prevalence of skin symptoms had decreased only subtly from 45 to 34%. We have studied the correlation between PPOX genotype and clinical outcome of 90 patients with the three most common Finnish mutations I12T, R152C and 338G-->C. The patients with the I12T mutation experienced no photosensitivity and acute attacks were rare (8%). Therefore, the occurrence of photosensitivity was lower in the I12T group compared to the R152C group (P=0.001), whereas no significant differences between the R152C and 338G-->C groups could be observed. Biochemical abnormalities were significantly milder suggesting a milder form of the disease in patients with the I12T mutation. In all VP patients, normal excretion of protoporphyrin in faeces in adulthood predicted freedom from both skin symptoms and acute attacks. The most valuable test predicting an increased risk of symptoms was urinary coproporphyrin, but only a substantially increased excretion exceeding 1,000 nmol/day was associated with an increased risk of both skin symptoms and acute attacks. All patients with an excretion of more than 1,000 nmol/day experienced either skin symptoms, acute attacks, or both.

Erythrocyte aminolevulinate dehydratase activity as a lead marker in patients with chronic renal failure

Background: Overexposure to lead may result in an increased risk for developing chronic renal failure (CRF) and hypertension. Subclinical lead poisoning is difficult to identify. Because the heme biosynthetic pathway is highly sensitive to lead, we considered the study of enzymes involved in this pathway as a method to detect an excessive body lead burden. Methods: Main concerns in assessing the heme pathway in patients with CRF were related to aminolevulinate dehydratase (ALAD) activity. We first selected a number of patients with CRF at a predialysis stage, subsequently dividing them into two groups after the EDTA mobilization test had determined whether lead pools were expanded. The study included 24 healthy controls, 12 patients with clinical plumbism and biochemical demonstration of lead poisoning (Pb-CONT), 18 patients with CRF with no evidence of high lead storage (CRF/−), and 8 patients with CRF with high urinary excretion of lead in contrast to normal blood lead levels (CRF/+). Results: As expected, symptoms of plumbism (Pb-CONT) were accompanied by an increased erythrocyte zinc-protoporphyrin-free protoporphyrin ratio and high urine coproporphyrin excretion, whereas both these values were within the normal range in all patients with CRF. CRF/− patients showed minor abnormalities of erythrocyte heme metabolism, such as low ALAD activity, both baseline and in vitro restored. The ALAD-restored ALAD ratio correlated closely with urine lead excretion; it was normal in healthy controls and CRF/− patients and significantly reduced in Pb-CONT and CRF/+ patients. Conclusion: The erythrocyte ALAD-restored ALAD ratio may be a useful tool to show otherwise subclinical lead poisoning in patients with CRF.© 2002 by the National Kidney Foundation, Inc.

Analysis of Urinary Porphyrins in Rats Exposed to Aluminum and Iron

The mechanism by which excess aluminum induces anemia may be aluminum overload resulting from a reversible block in heme synthesis due either to a defect in porphyrin synthesis or to impaired iron utilization. Studies were conducted to define the specific changes in the urinary porphyrin excretion pattern (porphyrin profile) and the time course of those changes in rats exposed to aluminum. In these studies, aluminum chloride (AlCl3) was orally administered to female Wistar rats at the dose of 100 mg Al/kg for 35 days with or without FeCl2 (4 mg Fe/kg). Control rats were treated with 0.9% NaCl or with FeCl2 (4 mg/kg). The dynamics of urine porphyrins (8-, 7-, 6-, 5-, and 4-carboxyporphyrins) was determined by HPLC on the 7th, 14th, 21st, 28th, and 35th days in both exposed and control groups of rats. The results of the experiment indicate that aluminum induced a statistically significant increase in the percentage of uroporphyrin and a decrease in coproporphyrin in urine (cumulative dose, 2100 mg Al/kg). Changes in urinary porphyrins were observed when the concentration of aluminum in serum was at 48 μg Al/L on average. Administration of iron together with aluminum diminished the described changes in porphyrins metabolism caused by aluminum itself.

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, δ-aminolevulinic acid (median = 84 μmol/24 h) and porphobilinogen (median = 39 μmol/24 h), as compared to controls (δ-aminolevulinic acid: 22 μmol/24 h, porphobilinogen: 3 μmol/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%).

Biomarkers of lead exposure.

Biomarkers of exposure, effect, and susceptibility are reviewed in relation to lead exposure. Of the biomarkers of lead exposure, blood lead (Pb-B), mainly red cell lead, is a representative of soft tissue lead, and most widely used as measures of body burden and absorbed (internal) doses of lead. Urine lead (Pb-U) as well as plasma lead (Pb-P) increases exponentially with increasing Pb-B under a steady-state situation and is a reflection of recent exposure. The amount of lead in plasma and urine (MPb-P and MPb-U) after administration of a chelating agent (e.g. CaEDTA) can be useful for biomarkers of internal exposure of lead, reflecting the mobilizable pool of lead which consists of mainly blood and soft tissue lead with only a small fraction derived from bones. The critical effects in bone marrow arise mainly from the interaction of lead with some enzymatic process responsible for heme synthesis. The effects can be used for the biomarkers of effects. They are the inhibition of delta-aminolevulinic acid dehydratase (ALAD) and the variation in some metabolite concentrations (e.g. delta-aminolevulinic acid in urine (ALA-U), blood (ALA-B) or plasma (ALA-P), coproporphyrin in urine (CP), zinc protoporphyrin (ZP) in blood). The activities of pyrimidine nucleotidase (P5'N) and nicotinamide adenine dinucleotide synthetase (NADS) in blood are also decreased in lead exposure, and nucleotide contents in blood is altered in lead exposure. These effects of lead on human can be also useful biomarkers of effect. The differences in levels of heme precursors between two types of ALAD genotypes might be attributable to those in the affinity of different ALAD isozymes to lead. ALAD1 homozygotes have higher levels of ZP and ALA in comparison with ALAD2 carriers at the high lead exposure, suggesting that ALAD1 homozygotes might be more susceptible for disturbance in heme biosynthesis by lead than ALAD2 carriers.

Diagnosis of variegate porphyria - hard to get?

Variegate porphyria (VP) is an inherited metabolic disease that results from the partial deficiency of protoporphyrinogen oxidase. In this communication we have used DNA technology in the diagnosis of VP and compared the results with the biochemical and clinical data. To date, we have diagnosed 107 VP patients using either biochemical or DNA techniques or both. In addition, in 106 family members the diagnosis of VP could be excluded. The sensitivity and specificity of the biochemical screening for VP were studied among 38 family members. These individuals were either asymptomatic (n=19) or had experienced occasional skin symptoms (n=13), acute attacks (n=5) or both (n=1). The sensitivity of urinary and fecal coproporphyrin analysis was 48% and 52%, respectively. The sensitivity of urinary uroporphyrin analysis was 71% and for fecal protoporphyrin 77%. Plasma fluorescence was sensitive in symptomatic patients even in remission, but resulted in false negatives in four asymptomatic patients with normal excretion of porphyrins in the urine. In our series of mutation screening, many new asymptomatic patients were identified, and this demonstrated that DNA analysis is the only reliable way to screen (a)symptomatic patients facilitating correct treatment and proper genetic counselling of family members at risk. Biochemical analyses (e.g. plasma fluorescence, fecal protoporphyrins, urinary copro- and uroporphyrins, porphobilinogen and delta-aminolevulinic acid) are essential when the diagnosis of VP is confirmed at the symptomatic phase.

Abnormal Uroporphyrin Levels in Chronic Hepatitis C Virus Infection

A strong association between hepatitis C virus (HCV) infection and porphyria cutanea tarda (PCT) has been observed, but the implications of the viral infection in the metabolism of porphyrins in patients without clinical manifestations of PCT are not known. The levels of porphyrin in plasma and uroporphyrin (URO) and coproporphyrin (COPRO) in 24-hour urine were measured in 156 patients with chronic HCV infection showing no clinical evidence of PCT. Levels of URO higher than the upper limit were observed in 35 of 156 patients (22.4%). The range and the mean values +/- standard deviation were 26-1,196 microg/24 hours and 82 +/- 204 microg/24 hours. Increased levels of COPRO and plasma porphyrin were observed in 12 of 156 patients (7.7%) and 2 of 156 patients (1.3%) respectively. There were no differences between patients with increased URO levels and patients with normal URO levels in terms of gender, age, risk factors for HCV infection, alcohol abuse, or hepatitis B viral infection. Transferrin saturation (p = 0.040), gamma glutamyl transpeptidase (p < 0.0001), aspartate aminotransferase (p = 0.006), and alanine aminotransferase (p = 0.040) were significantly higher in patients with abnormal URO than in patients with normal URO. The frequency of cirrhosis was higher, but not significantly different, in patients with increased URO (16.7%) compared with patients with normal URO (3.8%). The authors demonstrated that even without a clinical manifestation of PCT it is possible to detect abnormalities in the metabolism of porphyrins in patients with chronic HCV infection. The implications of these findings deserve additional investigation.