Urine concentrations of xanthine, hypoxanthine and uric acid in UK Cavalier King Charles spaniels.

OBJECTIVES: Xanthine urolithiasis and asymptomatic xanthinuria have been diagnosed in Cavalier King Charles spaniel dogs suggesting that primary xanthinuria may be a breed-related disorder, although its prevalence remains unclear. The hypothesis of this study was that asymptomatic xanthinuria is common in Cavalier King Charles spaniel dogs. METHODS: Free catch urine samples were collected from 35 client-owned Cavalier King Charles spaniel dogs and from 24 dogs of other breeds. The purine metabolites were measured by high-performance liquid chromatography. The urine ratios of xanthine/creatinine and hypoxanthine/creatinine were calculated and compared between the two groups of dogs. RESULTS: The urine concentrations of purine metabolites were not significantly different between the two groups and were very low in both. The urine concentrations of xanthine in all 35 Cavalier King Charles spaniel were markedly lower than in the previously reported case of xanthine urolithiasis in a UK Cavalier King Charles spaniel dog. CLINICAL SIGNIFICANCE: Asymptomatic xanthinuria was not detected in this UK Cavalier King Charles spaniel population. This data may be used as a reference for urinary purine metabolite concentrations in the dog.

An unusual genetic variant in the MOCS1 gene leads to complete missplicing of an alternatively spliced exon in a patient with molybdenum cofactor deficiency.

Molybdenum cofactor deficiency (MOCOD) is a rare inherited metabolic disorder resulting in the combined deficiency of aldehyde oxidase (AO, EC 1.2.3.1), xanthine dehydrogenase (XDH, EC 1.1.1.204), and sulfite oxidase (SUOX, EC 1.8.3.1). The majority of patients typically present soon after birth with intractable seizures, developmental delay and lens dislocation and do not survive early childhood. Milder cases have been reported. We report an unusual mutation in the MOCS1 gene associated with a relatively mild clinical phenotype, in a patient who presented with normal uric acid (UA) levels in plasma. We also report a new MOCS1 mRNA splice variant in the 5' region of the gene. MOCS1 genomic DNA and cDNA from peripheral blood leukocytes were sequenced. MOCS1 mRNA splice variants were amplified with fluorescently labelled primers and quantitated. A novel homozygous mutation MOCS1c.1165+6T > C in intron 9 resulting in miss-splicing of exon 9 was found. Multiple alternatively spliced MOCS1 transcripts have been previously reported. A new MOCS1 transcript in the 5' - exon 1 region was identified in both patient and controls. This new transcript derived from the Larin variant and lacked exon 1 d.

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.

The novel nucleotide 4KNTP, in high concentrations in erythrocytes of renal failure children: a comparison with accumulation of other putative precursors in the plasma.

We have measured the concentrations of metabolites related to the turnover of NAD, which accumulate in the blood of children with renal failure. One is a novel nucleotide, identified as the N1-riboside triphosphate of 4-pyridone-3-carboxamide (4PYTP), also described as 4KNTP, which accumulates in the erythrocytes in parallel with renal failure.

Familial juvenile hyperuricaemic nephropathy is not such a rare genetic metabolic purine disease in Britain.

Renal disease is rare today in classic adult gout, and gout is rare in renal disease--especially in the young. Here we summarise studies in 158 patients from 31 kindreds diagnosed with familial juvenile hyperuricaemic nephropathy FJHN from a total of 230 kindred members studied in Great Britain. Some patients have been followed for up to 30 years, and allopurinol has ameliorated the progression of the renal disease in all 113 surviving members provided: They have been diagnosed and treated sufficiently early. Compliance with allopurinol treatment and diet has been as important as early recognition. Hypertension has been rigorously controlled. The use of oral contraceptives has been avoided, as has pregnancy in any female with a Glomelar Filtration Rate GFR <70 ml/min. The question arising is: Why is FJHN the most prevalent genetic purine disorder diagnosed in Britain? Is it a lack of awareness which needs to be improved Europe-wide?

The neuroleptic chlorpromazine inhibits the cationic and stimulates the anionic phospholipid precursor synthesis in human lymphocytes.

The widely used neuroleptic drug chlorpromazine (CPZ) influences membrane functions at the levels of ionic channels and receptors as shown. Here we show the effect of short term treatments by CPZ (30 microM), on the nucleotide-containing phospholipid precursors in human lymphocyte primary cultures. During 60 minutes incubation of the cells, the CDP-ethanolamine (CDP-EA) content was only slightly reduced (87 to 76 pmol/10(6) cells), the amount of CDP-choline (CDP-Ch) was inhibited totally (from 25 to 0 pmol) upon the treatment with 30 microM CPZ under the same conditions. It has been shown earlier, that dCTP can be used as well as CTP for biosynthesis of phospholipids. Thus, the separation of the corresponding ribo- and deoxyribo-liponucleotides was developed. CPZ almost completely inhibited the synthesis of both dCDP-EA and dCDP-Ch under the same conditions The synthesis of the activated liponucleotide precursors, can be measured by incorporation of extracellular 14C-dCyt into both dCDP-EA and dCDP-Ch, as shown earlier. While the cationic deoxyribo-liponucleotide content (dCDP-Ch, dCDP-EA) was decreased, the labelling of the anionic phospholipid precursor dCDP-diacylglycerol (dCDP-DAG) was enhanced several times, it could be labelled only in the presence of CPZ from 14C-dCyd. Thus, a principal disturbance of the membrane phospholipid synthesis is presented (i.e., inhibition of the cationic and enhancement of the anionic dCDP-DAG synthesis). This profound influence on the membrane phospholipids by chlorpromazine, might be the primary effect that contributes to the wide spectrum of CPZ effects on neuronal cells.

HPRT deficiency as the cause of ESRD in a 24-year-old patient: a very rare presentation of the disorder.

A 24-year-old male with end-stage renal disease (ESRD) and disproportionately high uric acid plasma concentration was admitted to our unit. After studying the patient's medical history, as well as that of the entire family, hyperuricemia was discovered in his brother, while microscopic examination of his brother's and mother's urine revealed abundant uric acid crystals. After performing purine metabolic studies, it was determined that the two siblings suffered from partial hypoxanthine-guanine phosphoribosyltransferase (HPRT) deficiency (Kelley-Seegmiller syndrome). This report highlights the importance of clinical awareness and a thorough examination of the patient's medical history for establishing an early diagnosis and commencing treatment for such rare inherited metabolic disorders to prevent renal failure.

Nucleotide degradation products in cerebrospinal fluid (CSF) in inherited and acquired pathologies.

CSF purines were grossly elevated compared with controls only in adenylosuccinate lyase (ADSL) deficiency and TB meningitis. The former representing low permeability, the latter severe damage to the normal blood/brain barrier. By contrast, the similarity to controls, with no difference between Lesch-Nyhan disease (LND) or LND variants, would exclude hypoxia as a factor in the severe neurological deficits in LND. Similar findings in purine nucleoside phosphorylase (PNP) deficiency (although nucleosides replace the normal bases) likewise exclude hypoxia in the aetiology of the albeit milder neurological deficits.

Adenylosuccinate lyase deficiency--first British case.

A deficiency of adenylosuccinate lyase (ASDL) is characterised by the accumulation of SAICAriboside (SAICAr) and succinyladenosine (S-Ado) in body fluids. The severity of the clinical presentation correlates with a low S-Ado/SAICAr ratio in body fluids. We report the first British case of ADSL deficiency. The patient presented at 14 days with a progressive neonatal encephalopathy and seizures. There was marked axial and peripheral hypotonia. Brain MRI showed widespread white matter changes. She died at 4 weeks of age. Concentrations of SAICAr and SAdo were markedly elevated in urine, plasma and CSF and the SAdo/SAICAr ratio was low, consistent with the severe phenotype. The patient was compound heterozygous for 2 novel ADSL mutations; c.9 G>C (A3P) and c.572 C>T (R190X).

Mutation in the ITPA gene predicts intolerance to azathioprine.

Inosine triphosphate pyrophosphatase (ITPase) deficiency occurs with polymorphic frequencies in Caucasians and results in the benign accumulation of the inosine nucleotide ITP. In 62 patients treated with azathioprine for inflammatory bowel disease, the ITPA 94C>A deficiency-associated allele was significantly associated with adverse drug reactions (OR 4.2, 95% CI 1.6-11.5, p = 0.0034). Significant associations were found for flu-like symptoms (OR 4.7, 95% CI 1.2-18.1, p = 0.0308), rash (OR 10.3, 95% CI 4.7-62.9, p = 0.0213) and pancreatitis (OR 6.2, CI 1.1-32.6, p = 0.0485). Polymorphism in the ITPA gene thus predicts AZA intolerance. Alternative immunosuppressive drugs, particularly 6-thioguanine, should be considered for AZA-intolerant patients with ITPase deficiency.

A novel missense mutation, c.584A > C (Y195S), in two unrelated Argentine patients with hypoxanthine-guanine phosphoribosyl-transferase deficiency, neurological variant.

The hypoxanthine-guanine phosphoribosyl-transferase (HPRT) deficiency is an inborn error of purine metabolism, responsible for classic Lesch-Nyhan disease and its neurological and hyperuricemic variants. We report a novel mutation in the HPRT gene, c.584A > C (Y195S), in two unrelated Argentine patients affected with the neurological variant with no HPRT activity in lysed erythrocytes. Using PCR plus DNA sequencing and/or restriction enzyme digestion we were able to confirm the diagnosis and identify new cases and potential carriers.

Early treatment with allopurinol in familial juvenile hyerpuricaemic nephropathy (FJHN) ameliorates the long-term progression of renal disease.

BACKGROUND: The efficacy of allopurinol in autosomal dominant familial juvenile hyperuricaemic nephropathy (FJHN) has been disputed. AIM: To address this question, in the absence of controlled trials. DESIGN: Retrospective long-term follow-up study. METHODS: All kindreds were biochemically screened. Measurements included uric acid clearance, creatinine clearance, serum creatinine, and glomerular filtration rate (GFR). We used five siblings who had died or progressed to transplantation, ten other deceased relatives, and two index cases (one untreated, one non-compliant) as controls to assess the effects of allopurinol. RESULTS: Of eight families with FJHN, six had a strong history of renal disease and early parental death (mean age 41 years, n=10). Of 27 patients started immediately on allopurinol and treated uninterruptedly, 21 responded well, including three children born subsequently. Eight siblings (mean age 19 years) with a normal plasma creatinine at start (<120 micromol/l, mean GFR 80 ml/min/1.73 m(2)) retained stable renal function (mean 14.5 years, mean age 34 years, GFR 85 ml/min/1.73 m(2)). Of the 13 other responders, treated for up to 34 years, 10 with a creatinine <200 micromol/l at diagnosis (mean age 28 years, mean creatinine 137 micromol/l at start) now have a mean creatinine of 210 micromol/l. In contrast, five patients (mean age 26 years) with a creatinine >200 micromol/l (GFR <35 ml/min/1.73 m(2)) when allopurinol commenced, plus one untreated index case, all progressed rapidly (mean 6 years) to end-stage renal failure. In two others (one non-compliant, one initially untreated), GFR fell by >50% in 7 years. Introduction of allopurinol in the latter has stabilized GFR. DISCUSSION: Allopurinol reduced the morbidity and mortality from renal failure seen in untreated siblings and previous generations of these families. Early diagnosis of FJHN is important, so that treatment can begin before irreversible renal damage has developed.

In vitro and in vivo studies with human carrier erythrocytes loaded with polyethylene glycol-conjugated and native adenosine deaminase.

Polyethylene glycol-conjugated adenosine deaminase (pegademase) is used for enzyme replacement therapy for patients with severe combined immunodeficiency caused by adenosine deaminase deficiency. The entrapment of pegademase within human energy-replete carrier erythrocytes using a hypo-osmotic dialysis procedure was investigated with the objective of prolonging the in vivo circulatory half-life of the enzyme and maintaining therapeutic blood levels. Native unmodified adenosine deaminase (ADA) was similarly studied. The efficiency of pegademase entrapment was low (9%) whereas the entrapment of native unmodified ADA was substantial (50%), suggesting that the polyethylene glycol side-chains were impeding intracellular entrapment. The biochemical characteristics and the osmotic fragility of these carrier erythrocytes were not adversely affected by the entrapment of either pegademase or native ADA. In vivo survival studies of pegademase-loaded 51Cr-labelled carrier erythrocytes in an ADA-deficient adult patient showed a mean cell half-life of 16 d. Carrier erythrocyte-entrapped pegademase and native ADA had in vivo half-lives of 20 and 12.5 d, respectively, demonstrating that entrapment prolongs the half-life over that of plasma pegademase, which has a circulating half-life of 3-6 d. These results provide the basis for a more extensive clinical evaluation of carrier erythrocyte-entrapped native adenosine deaminase therapy.