Efficacy and safety of allopurinol in patients with the Lesch-Nyhan syndrome and partial hypoxanthine- phosphoribosyltransferase deficiency: a follow-up study of 18 Spanish patients

Allopurinol is used widely for the treatment of purine disorders such as gout, but efficacy and safety of allopurinol has not been analyzed systematically in an extensive series of patients with HPRT deficiency. From 1984 to 2004 we have diagnosed 30 patients with HPRT deficiency. Eighteen patients (12 with Lesch-Nyhan syndrome or complete HPRT deficiency, and 6 with partial HPRT deficiency) were treated with allopurinol (mean dose, 6.44 mg/Kg of weight per day) and followed-up for at least 12 months (mean follow-up 7,6 years per patient). Mean age at diagnosis was 7 years (range, 5 months to 35 years). Treatment with allopurinol was associated to a mean reduction of serum urate concentration of 50%, and was normalized in all patients. Mean urinary uric acid excretion was reduced by 75% from baseline values, and uric acid to creatinine ratio was close or under 1.0 in all patients. In contrast, hypoxanthine and xanthine urinary excretion rates increased by a mean of 6 and 10 times, respectively, compared to baseline levels. These modifications were similar in patients with complete or partial HPRT deficiency. In 2 patients xanthine stones were documented despite allopurinol dose adjustments to prevent markedly increased oxypurine excretion rates. Neurological manifestations did not appear to be influenced by allopurinol therapy. Allopurinol is a very efficacy and fairly safety drug for the treatment of uric acid overproduction in patients with complete and partial HPRT deficiency. Allopurinol was associated with xanthine lithiasis.     

The diagnosis of HPRT deficiency in the 21st century

We have studied 36 patients with HPRT deficiency, 25 with Lesch-Nyhan syndrome and 11 with partial HPRT deficiency (grades 1 to 3). Patients diagnosed with HPRT deficiency have increased 50% since 2000. The most relevant recent advances have been made in molecular diagnosis. Nevertheless, enzyme determinations are still essential for the diagnosis of HPRT deficiency. Therapy for the neurological manifestations of HPRT deficiency has not advanced. Allopurinol remains the drug of choice to diminish uric acid overproduction, but the optimal allopurinol dose must be established in each patient to prevent xanthine or uric acid urolithiasis, a process aided by sequential determination of urinary oxypurines and uric acid.     

The Diagnosis Of HPRT Deficiency in the 21St Century

We have studied 36 patients with HPRT deficiency, 25 with Lesch-Nyhan syndrome and 11 with partial HPRT deficiency (grades 1 to 3). Patients diagnosed with HPRT deficiency have increased 50% since 2000. The most relevant recent advances have been made in molecular diagnosis. Nevertheless, enzyme determinations are still essential for the diagnosis of HPRT deficiency. Therapy for the neurological manifestations of HPRT deficiency has not advanced. Allopurinol remains the drug of choice to diminish uric acid overproduction, but the optimal allopurinol dose must be established in each patient to prevent xanthine or uric acid urolithiasis, a process aided by sequential determination of urinary oxypurines and uric acid.     

Chemical diagnosis of Lesch-Nyhan syndrome using gas chromatography-mass spectrometry detection

Lesch-Nyhan syndrome (LNS) is caused by a severe deficiency of hypoxanthine-guanine phosphoribosyltransferase (HPRT) and clinically characterized by self-injurious behavior and nephrolithiasis; the latter is treatable with allopurinol, an inhibitor of xanthine oxidase which converts xanthine and hypoxanthine into uric acid. In the HPRT gene, more than 200 different mutations are known, and de novo mutation occurs at a high rate. Thus, there is a great need to develop a highly specific method to detect patients with HPRT dysfunction by quantifying the metabolites related to this enzyme. A simplified urease pretreatment of urine, gas chromatography-mass spectrometry, and stable isotope dilution method, developed for cutting-edge metabonomics, was further applied to quantify hypoxanthine, xanthine, urate, guanine and adenine in 100 microl or less urine or eluate from filter-paper-urine strips by additional use of stable isotope labeled guanine and adenine as the internal standards. In this procedure, the recoveries were above 93% and linearities (r(2)=0.9947-1.000) and CV values (below 7%) of the indicators were satisfactory. In four patients with proven LNS, hypoxanthine was elevated to 8.4-9.0 SD above the normal mean, xanthine to 4-6 SD above the normal mean, guanine to 1.9-3.7 SD, and adenine was decreased. Because of the allopurinol treatment for all the four patients, their level of urate was not elevated, orotate increased, and uracil was unchanged as compared with the control value. It was concluded that even in the presence of treatment with allopurinol, patients with LNS can be chemically diagnosed by this procedure. Abnormality in the levels of hypoxanthine and xanthine was quite prominent and n, the number of standard deviations above the normal mean, combined for the two, was above 12.9.     

Effects of allopurinol on beer-induced increases in plasma concentrations and urinary excretion of purine bases (uric acid, hypoxanthine, and xanthine).

To determine the effects of allopurinol on beer-induced increases in plasma and urinary excretion of purine bases (hypoxanthine, xanthine, and uric acid), we performed three experiments on five healthy study participants. In the first experiment (combination study), the participants ingested beer (10 ml/kg body weight) eleven hours after taking allopurinol (300 mg). In the second experiment (beer-only study), the same participants ingested beer (10 ml/kg body weight) alone, while in the third experiment (allopurinol-only study), they took allopurinol (300 mg) alone. There was a two-week interval between each of the studies. Beer-induced increases in plasma concentration and urinary excretion of hypoxanthine in the combination study were markedly higher than those in the beer-only study. On the other hand, the sum of increases in plasma concentrations of purine bases in the beer-only study was greater than in the combination study, whereas the increase in plasma uridine concentration in the combination study did not differ from the beer-only study. In addition, allopurinol administration inhibited the beer-induced increase in plasma concentration of uric acid. These results suggest that abrupt adenine nucleotide degradation may increase plasma concentration and urinary excretion of hypoxanthine under conditions of low xanthine dehydrogenase activity, which is mostly ascribable to allopurinol. Further, the difference in the sum of increases in plasma concentrations of purine bases between the combination study and beer-only study was largely ascribable to a greater increase in urinary excretion of hypoxanthine in the combination study. In addition, allopurinol intake seems to be effective in controlling the rapid increase in plasma uric acid caused by ingestion of alcoholic beverages.     

Hypoxanthine-Guanine Phosphoribosyltransferase Deficiency: Biochemical and Molecular Findings in Six Argentine Patients

Hypoxanthine-guanine phosphoribosyltransferase (HPRT) deficiency is an inborn error of purine metabolism responsible for Lesch-Nyhan Disease (LND) and its partial phenotypes, HPRT-related hyperuricemia with neurologic dysfunction (HRND) and hyperuricemia alone. We report here the recognition of six Argentine patients, two with LND and four with HRND. All patients presented elevated excretion of uric acid, hypoxanthine, and xanthine and decreased HPRT enzyme activities <1 nmol/h/mg Hb. The molecular analysis demonstrated in the two LND patients a novel inherited transition mutation, c.203T >C (L68P), in one subject and a germline transition mutation, c.209G >A (G70E), in the other. In the HRND patients a novel transversion mutation, c.584 A >C (Y195S), was found in three related patients and an inherited transition mutation, c.143G >A (R48H), in the fourth subject.     

Unusual presentation of Kelley-Seegmiller syndrome

Female carriers of hypoxanthine-guanine phosphoribosyltransferase (HPRT) deficiency have somatic cell mosaicism of HPRT activity and are healthy. We report a 50-year-old woman without gout or nephrolithiasis. She was never on allopurinol. Normal serum uric acid concentrations, increased plasma hypoxanthine, and xanthine were found. HPRT activity in erythrocytes was surprisingly low: at 8.6 nmol h(-1) mg (-1) haemoglobin. Mutation analysis revealed a heterozygous HPRT gene mutation, c.215A > G (p.Tyr72Cys). Assessment of X-inactivation ratio has shown that > 75% of the active X-chromosome bears the mutant allele and could explain these unusual, previously undescribed findings.     

The Treatment of Gout and Disorders of Uric Acid Metabolism with Allopurinol

Allopurinol (4-hydroxypyrazolo (3,4-d)-pyrimidine) is a potent xanthine oxidase inhibitor which inhibits the oxidation of naturally occurring oxypurines, thus decreasing uric acid formation. The clinical and metabolic effects of this agent were studied in 80 subjects with primary and secondary gout and other disorders of uric acid metabolism. Allopurinol has been universally successful in lowering the serum uric acid concentration and uric acid excretion to normal levels, while not significantly affecting the clearance of urate or other aspects of renal function. Oxypurine excretion increased concomitantly with the fall in urine uric acid. The agent is particularly valuable in the management of problems of gout with azotemia, acute uric acid nephropathy and uric acid urolithiasis. The minor side effects, clinical indications and theoretical complications are discussed.     

Management of Hyperuricemia with Rasburicase Review

Tumor lysis syndrome (TLS) is a serious complication in patients with hematological malignancies. Massive lysis of tumor cells can lead to hyperuricemia, hyperkalemia, hyperphosphatemia and hypocalcaemia. These metabolic disturbances may result in renal failure, because of precipitation of uric acid crystals and calcium phosphate salts in the kidney. The standard prophylaxis or treatment of hyperuricemia consists of decreasing uric acid production with allopurinol and facilitating its excretion by urinary alkalinization and hyperhydration. By inhibiting the enzyme xanthine oxidase, allopurinol blocks the conversion of hypoxanthine and xanthine into uric acid. An alternative treatment is urate oxidase which oxidates uric acid into allantoin. Allantoin is 5–10 times more soluble than uric acid and is therefore excreted easily. In several clinical trials rasburicase, the recombinant form of urate oxidase, has shown to be very effective in preventing and treating hyperuricemia. Rasburicase, in contrast with the non‐recombinant form of urate oxidase uricozyme, is associated with a low incidence of hypersensitivity reactions. In addition to the demonstrated clinical benefit, rasburicase also proved to be a cost‐effective option in the management of hyperuricemia.     

Management of hyperuricemia with rasburicase review

Tumor lysis syndrome (TLS) is a serious complication in patients with hematological malignancies. Massive lysis of tumor cells can lead to hyperuricemia, hyperkalemia, hyperphosphatemia and hypocalcaemia. These metabolic disturbances may result in renal failure, because of precipitation of uric acid crystals and calcium phosphate salts in the kidney. The standard prophylaxis or treatment of hyperuricemia consists of decreasing uric acid production with allopurinol and facilitating its excretion by urinary alkalinization and hyperhydration. By inhibiting the enzyme xanthine oxidase, allopurinol blocks the conversion of hypoxanthine and xanthine into uric acid. An alternative treatment is urate oxidase which oxidates uric acid into allantoin. Allantoin is 5-10 times more soluble than uric acid and is therefore excreted easily. In several clinical trials rasburicase, the recombinant form of urate oxidase, has shown to be very effective in preventing and treating hyperuricemia. Rasburicase, in contrast with the non-recombinant form of urate oxidase uricozyme, is associated with a low incidence of hypersensitivity reactions. In addition to the demonstrated clinical benefit, rasburicase also proved to be a cost-effective option in the management of hyperuricemia.     

Hypoxanthine-guanine phosphoribosyltransferase deficiency: biochemical and molecular findings in six Argentine patients

Hypoxanthine-guanine phosphoribosyltransferase (HPRT) deficiency is an inborn error of purine metabolism responsible for Lesch-Nyhan Disease (LND) and its partial phenotypes, HPRT-related hyperuricemia with neurologic dysfunction (HRND) and hyperuricemia alone. We report here the recognition of six Argentine patients, two with LND and four with HRND. All patients presented elevated excretion of uric acid, hypoxanthine, and xanthine and decreased HPRT enzyme activities <1 nmol/h/mg Hb. The molecular analysis demonstrated in the two LND patients a novel inherited transition mutation, c.203T >C (L68P), in one subject and a germline transition mutation, c.209G >A (G70E), in the other. In the HRND patients a novel transversion mutation, c.584 A >C (Y195S), was found in three related patients and an inherited transition mutation, c.143G >A (R48H), in the fourth subject.     

Biochemical studies on bilharzial and nonbilharzial hyperoxaluria: effect of pyridoxine and allopurinol treatment

The urinary excretion levels of oxalic acid, calcium, kynurenic, and xanthurenic acids and serum pyridoxal and pyridoxal phosphate concentrations were determined for nonbilharzial and bilharzial hyperoxaluric patients with or without urinary stones. The effects of pyridoxine and allopurinol treatment were also studied. The different groups studied showed elevated levels of urinary oxalic acid, calcium, kynurenic, and xanthurenic acids as well as decreases in serum pyridoxal and pyridoxal phosphate concentrations. These data indicate that nonbilharzial hyperoxaluric patients suffer from dietary B6 deficiency, whereas bilharzial hyperoxaluric patients may suffer from impaired pyridoxine phosphokinase activity. Pyridoxine supplementation is recommended for the treatment of nonbilharzial hyperoxaluric patients. Allopurinol may be the proper drug in the treatment of oxaluria and stone formation or of bilharzial patients.     

Unusual Presentation of Kelley-Seegmiller Syndrome

Female carriers of hypoxanthine-guanine phosphoribosyltransferase (HPRT) deficiency have somatic cell mosaicism of HPRT activity and are healthy. We report a 50-year-old woman without gout or nephrolithiasis. She was never on allopurinol. Normal serum uric acid concentrations, increased plasma hypoxanthine, and xanthine were found. HPRT activity in erythrocytes was surprisingly low: at 8.6 nmol h^?1 mg ^?1 haemoglobin. Mutation analysis revealed a heterozygous HPRT gene mutation, c.215A > G (p.Tyr72Cys). Assessment of X-inactivation ratio has shown that > 75% of the active X-chromosome bears the mutant allele and could explain these unusual, previously undescribed findings.     

Febuxostat (TMX-67), a novel, non-purine, selective inhibitor of xanthine oxidase, is safe and decreases serum urate in healthy volunteers

In order to evaluate the safety, pharmacological properties, and urate-lowering efficacy of febuxostat, a non-purine, selective inhibitor of xanthine oxidase, a Phase 1, 2-week, multiple-dose, placebo-controlled, dose-escalation study was conducted in 154 healthy adults of both sexes. Daily febuxostat doses in the range 10 mg to 120 mg resulted in proportional mean serum urate reductions ranging from 25% to 70% and in proportional increases in maximum febuxostat plasma concentrations and area under plasma concentration versus time curves. Accompanying the hypouricemic effect were increases in serum xanthine concentrations, decreases in urinary uric acid excretion, and increases in urinary xanthine and hypoxanthine excretion, confirming inhibition of xanthine oxidase activity by febuxostat. Hepatic conjugation and oxidative metabolism were the major pathways of elimination of febuxostat from the body, and renal elimination did not appear to play a significant role. Although not uncommon, adverse events were mild and self-limited, and no deaths or serious adverse events were observed. Febuxostat is a safe and potent hypouricemic agent in healthy humans.     

Effects of long-term beer ingestion on plasma concentrations and urinary excretion of purine bases.

To investigate the long-term effects of beer ingestion on plasma concentrations of purine bases (hypoxanthine, xanthine, and uric acid), ten healthy males ingested beer (15 ml/kg body weight) every evening for three months. Blood and 24-hour urine samples were collected in the morning on one day before and one, two, and three months after starting the experiment to determine the plasma concentrations and urinary excretion of uric acid, hypoxanthine, and xanthine. Plasma concentrations and urinary excretion of uric acid, hypoxanthine, and xanthine in five of the participants that did not regularly ingest beer at a quantity of more than 15 ml/kg body weight in a single day prior to the experiment were not increased during the experimental period. In contrast, plasma concentrations and urinary excretion of uric acid were increased in five participants who regularly ingested more than 15 ml/kg body weight of beer in a single day prior to the experiment, although hypoxanthine and xanthine levels were not significantly increased during the experimental period. In both groups, uric acid clearance and purine ingestion were not significantly different throughout the study. Our results suggest that the production of uric acid caused by ethanol ingestion from beer is a significant contributor to the increase in plasma uric acid concentration in patients that regularly consume more than 15 ml/kg body weight of beer each day. Therefore, patients with gout should be encouraged to refrain from drinking large amounts of beer on a daily basis.     

Effect of purine-free low-malt liquor (happo-shu) on the plasma concentrations and urinary excretion of purine bases and uridine--comparison between purine-free and regular happo-shu.

To determine whether purine-free and regular low-malt liquor beverages (happo-shu) increase the plasma concentration and urinary excretion of purine bases (hypoxanthine, xanthine, uric acid) and uridine, 6 healthy males were given regular (10 ml/kg of body weight) and purine-free happo-shu (10 ml/kg of body weight). Plasma concentration-time curves were plotted, and the areas under the curves for uric acid and total purine bases (the sum of hypoxanthine, xanthine, and uric acid) were greater in the regular than in the purine-free happo-shu ingestion experiment (both p < 0.05). In addition, the total urinary excretion of xanthine, total purine bases, and uridine was greater in the regular than in the purine-free happo-shu ingestion experiment (p < 0.05 in all cases), although the total urinary excretion of hypoxanthine and uric acid was no different between the regular and the purine-free happo-shu ingestion experiments. These results suggest that uridine contained in regular happo-shu might contribute to an increase in the urinary excretion of uridine along with ethanol, and that the purines contained in regular happo-shu may contribute to the increase in plasma concentration of uric acid due to purine degradation.     

Urinary excretion of methylated purines in man and in the rat after the administration of theophylline

Chromatographic characteristics of urinary metabolites of theophylline were studied by two-dimensional thin-layer chromatography, high-performance liquid chromatography and gas chromatography—mass spectrometry. Quantitative data for the urinary metabolites of theophylline in asthmatic children are given. It was shown that 1,3-dimethyluric acid is the predominant excretory product. In addition, smaller amounts of 1-methyluric acid, 3-methylxanthine and unchanged theophylline were found.Excretory patterns after theophylline ingestion before and during the administration of allopurinol in asthma patients and in rats suggest the existence of three metabolic pathways of theophylline. The administration of this drug to a patient with xanthine oxidase deficiency resulted in the excretion of 1-methyluric acid in addition to 1,3-dimethyluric acid, 3-methylxanthine, 1-methylxanthine and unchanged theophylline. It was concluded that in man the oxidation of theophylline is not catalysed by xanthine oxidase.     

Febuxostat (TMX‐67), a Novel,Non‐Purine,Selective Inhibitor of Xanthine Oxidase,Is Safe and Decreases Serum Urate in Healthy Volunteers

In order to evaluate the safety, pharmacological properties, and urate‐lowering efficacy of febuxostat, a non‐purine, selective inhibitor of xanthine oxidase, a Phase 1, 2‐week, multiple‐dose, placebo‐controlled, dose‐escalation study was conducted in 154 healthy adults of both sexes. Daily febuxostat doses in the range 10 mg to 120 mg resulted in proportional mean serum urate reductions ranging from 25% to 70% and in proportional increases in maximum febuxostat plasma concentrations and area under plasma concentration versus time curves. Accompanying the hypouricemic effect were increases in serum xanthine concentrations, decreases in urinary uric acid excretion, and increases in urinary xanthine and hypoxanthine excretion, confirming inhibition of xanthine oxidase activity by febuxostat. Hepatic conjugation and oxidative metabolism were the major pathways of elimination of febuxostat from the body, and renal elimination did not appear to play a significant role. Although not uncommon, adverse events were mild and self‐limited, and no deaths or serious adverse events were observed. Febuxostat is a safe and potent hypouricemic agent in healthy humans.     

Hereditary xanthinuria is not so rare disorder of purine metabolism

Hereditary xanthinuria (type I) is caused by an inherited deficiency of the xanthine oxidorectase (XDH/XO), and is characterized by very low concentration of uric acid in blood and urine and high concentration of urinary xanthine, leading to urolithiasis. Type II results from a combined deficiency of XDH/XO and aldehyde oxidase. Patients present with hematuria, renal colic, urolithiasis or even acute renal failure. Clinical symptoms are the same for both types. In a third type, clinically distinct, sulfite oxidase activity is missing as well as XDH/XO and aldehyde oxidase. The prevalence is not known, but about 150 cases have been described so far. Hypouricemia is sometimes overlooked, that´s why we have set up the diagnostic flowchart. This consists of a) evaluation of uric acid concentrations in serum and urine with exclusion of primary renal hypouricemia, b) estimation of urinary xanthine, c) allopurinol loading test, which enables to distinguish type I and II; and finally assay of xanthine oxidoreductase activity in plasma with molecular genetic analysis. Following this diagnostic procedure we were able to find first patients with hereditary xanthinuria in our Czech population. We have detected nine cases, which is one of the largest group worldwide. Four patients were asymptomatic. All had profound hypouricemia, which was the first sign and led to referral to our department. Urinary concentrations of xanthine were in the range of 170–598 mmol/mol creatinine (normal < 30 mmol/mol creatinine). Hereditary xanthinuria is still unrecognized disorder and subjects with unexplained hypouricemia need detailed purine metabolic investigation.     

Urinary Guanidinoacetate and Creatine Levels in Patients with HPRT Deficiency

Neurobehavioral manifestations of complete HPRT deficiency include severe action dystonia, choreathetosis, alteration of executive functions, and self-injurious behavior. Dystonic manifestations are also present in patients with partial HPRT deficiency. Pathophysiology of these manifestations is unknown. Guanidinoacetate is a neurotoxin implicated in certain dystonic syndromes. We have examined guanidinoacetate and creatine levels in urine from 11 HPRT deficient patients (9 with Lesch-Nyhan syndrome and 2 with partial deficiency). Urinary guanidinoacetate and creatine levels in HPRT deficient patients were within the normal range. Guanidinoactetate alteration does not seem to be implicated in the pathogenesis of the neurological disease associated with HPRT deficiency.