Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0018099 (gout)
 5,192 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Although gout and hyperuricaemia are usually thought of as conditions of indulgent male middle age, in addition to the well-known uricosuria of the newborn, there is much of importance for the paediatric nephrologist in this field. Children and infants may present chronically with stones or acutely with renal failure from crystal nephropathy, as a result of inherited deficiencies of the purine salvage enzymes hypoxanthine-guanine phosphoribosyltransferase (HPRT) and adenine phosphoribosyltransferase (APRT) or of the catabolic enzyme xanthine dehydrogenase (XDH). Genetic purine overproduction in phosphoribosylpyrophosphate synthetase superactivity, or secondary to glycogen storage disease, can also present in infancy with renal complications. Children with APRT deficiency may be difficult to distinguish from those with HPRT deficiency because the insoluble product excreted, 2,8-dihydroxyadenine (2,8-DHA), is chemically very similar to uric acid. Moreover, because of the high uric acid clearance prior to puberty, hyperuricosuria rather than hyperuricaemia may provide the only clue to purine overproduction in childhood. Hyperuricaemic renal failure may be seen also in treated childhood leukaemia and lymphoma, and iatrogenic xanthine nephropathy is a potential complication of allopurinol therapy in these conditions. The latter is also an under-recognised complication of treatment in the Lesch-Nyhan syndrome or partial HPRT deficiency. The possibility of renal complications in these three situations is enhanced by infection, the use of uricosuric antibiotics and dehydration consequent upon fever, vomiting or diarrhoea. Disorders of urate transport in the renal tubule may also present in childhood. A kindred with X-linked hereditary nephrolithiasis, renal urate wasting and renal failure has been identified, but in general, the various rare types of net tubular wasting of urate into the urine are recessive and relatively benign, being found incidentally or presenting as colic from crystalluria. However, the opposite condition of a dominantly inherited increase in net urate reabsorption is far from benign, presenting as familial renal failure, with hyperuricaemia either preceding renal dysfunction or disproportionate to it. Paediatricians need to be aware of the lower plasma urate concentrations in children compared with adults when assessing plasma urate concentrations in childhood and infancy, so that early hyperuricosuria is not missed. This is of importance because most of the conditions mentioned above can be treated successfully using carefully controlled doses of allopurinol or means to render urate more soluble in the urine. Xanthine and 2,8-DHA are extremely insoluble at any pH. Whilst 2,8-DHA formation can also be controlled by allopurinol, alkali is contraindicated. A high fluid, low purine intake is the only possible therapy for XDH deficiency.
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PMID:Gout, uric acid and purine metabolism in paediatric nephrology. 843 71

Phosphoribosylpyrophosphate (PRPP) synthetase (PRS) superactivity is an X-linked disorder characterized by gout with overproduction of purine nucleotides and uric acid. Study of the two X-linked PRS isoforms (PRS1 and PRS2) in cells from certain affected individuals has shown selectively increased concentrations of structurally normal PRS1 transcript and isoform, suggesting that this form of the disorder involves pretranslational dysregulation of PRPS1 expression and might be more appropriately termed overactivity of normal PRS. We applied Southern and Northern blot analyses and slot blotting of nuclear runoffs to delineate the process underlying aberrant PRPS1 expression in fibroblasts and lymphoblasts from patients with overactivity of normal PRS. Neither PRPS1 amplification nor altered stability or processing of PRS1 mRNA was identified, but PRPS1 transcription was increased relative to GAPDH (3- to 4-fold normal in fibroblasts; 1.9- to 2.4-fold in lymphoblasts) and PRPS2. Nearly coordinate relative increases in each process mediating transfer of genetic information from PRPS1 transcription to maximal PRS1 isoform expression in patient fibroblasts further supported the idea that accelerated PRPS1 transcription is the major aberration leading to PRS1 overexpression. In addition, modulated relative increases in PRS activities at suboptimal Pi concentration and in rates of PRPP and purine nucleotide synthesis in intact patient fibroblasts indicate that despite an intact allosteric mechanism of regulation of PRS activity, PRPS1 transcription is a major determinant of PRPP and purine synthesis. The genetic basis of disordered PRPS1 transcription remains unresolved; normal- and patient-derived PRPS1s share nucleotide sequence identity at least 850 base pairs 5' to the consensus transcription initiation site.
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PMID:Accelerated transcription of PRPS1 in X-linked overactivity of normal human phosphoribosylpyrophosphate synthetase. 1006 14

Plasma uric acid concentration aggregates in families, and this similarity has been suggested to be due, in part, to multiple shared genes. Men have higher plasma uric acid concentrations than women and are affected with gout nine times more frequently. Rare forms of hyperuricemia and gout are due to mutations of X-linked genes (HPRT1 and PRPS1). Given these observations, we tested the hypothesis that normal variation in plasma uric acid levels would display a pattern of familial similarity consistent with X-linkage in 892 individuals from 196 obese but otherwise healthy families. As predicted by X-linked inheritance, fathers and sons showed no resemblance in plasma uric acid concentration (r = 0.013, NS), while all other pairings showed moderate-to-strong familial resemblance (ranging from 0.167, P < 0.01, parent-offspring to 0.415, sister-sister, P < 0.01). We then tested the hypothesis that loci along the X chromosome would influence plasma uric acid concentration. We conducted both single-point and multipoint linkage analyses using 17 X-linked markers spaced at approximately 9 cm intervals to determine whether allele sharing among sibs was related to sib similarity in plasma uric acid concentrations (n = 1,100 sib pairs). We found no regions of the X chromosome that cosegregated with plasma uric acid concentrations (P > 0.05). We conclude that variation in genes on the X chromosome contribute little to normal variation in plasma uric acid concentrations.
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PMID:X-linkage does not account for the absence of father-son similarity in plasma uric acid concentrations. 1079 40

Hypoxanthine-guanine phosphoribosyltransferase (HPRT) deficiency is an X-linked defect of purine metabolism. Clinical manifestations are usually related to the degree of enzyme deficiency: complete HPRT deficiency (Lesch-Nyhan syndrome) presenting with severe neurologic or renal symptoms, or partial HPRT deficiency (Kelley-Seegmiller syndrome) manifesting as a gout-urolithiasis syndrome. A 3-generation kindred is described in which the recognition of partial HPRT deficiency in 2 adolescent male siblings presenting with uric acid lithiasis led to the diagnosis in 2 maternal uncles already in renal failure of unknown cause. This report highlights the importance of clinical awareness leading to early diagnosis, appropriate diagnostic methodology, and therapy of a treatable inherited disorder of purine metabolism for the prevention of renal failure.
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PMID:Partial hypoxanthine-Guanine phosphoribosyltransferase deficiency as the unsuspected cause of renal disease spanning three generations: a cautionary tale. 1177 85

Lesch-Nyhan syndrome (LSN, McKusick 300322) is an X-linked genetic disease due, in its typical form, to the complete absence of hypoxanthine-guanine phosphoribosyltransferase (HPRT, EC 2.4.2.8) enzyme activity. It is characterized by hyperuricaemia, leading to gout and kidney stones, accompanied by severe neurological dysfunction with self-injurious behaviour, choreoathetosis and spasticity. Based on a worldwide birth incidence estimate of about 1:380000, one or two new cases are expected every year in Italy. We performed biochemical and molecular genetic studies on 28 Italian patients from 25 families who are likely to represent most living individuals with the syndrome in the country. They all had absent HPRT activity and a typical LNS phenotype. Genetic analysis identified 24 HPRT mutations, 9 of which had not been previously reported: 74C>G (P25R), IVS2+1G>C, 194-195delTC, 329-332delCAAC insTCTs, IVS9-1G>A, 506insC, IVS8-1G>C, 606G>T (L202F), 418G>C (G140R). No mutation hotspots were identified. Only two mutations were found in more than one family, indicating the lack of any major mutation causing LNS in Italy. Three mutations arose de novo , two in the proband's mother, one in the maternal grandmother. The virtual complete absence of HPRT activity was related to deletions, nonsense, or missense mutations leading to nonconservative amino acid changes.
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PMID:Molecular basis of hypoxanthine-guanine phosphoribosyltransferase deficiency in Italian Lesch-Nyhan patients: identification of nine novel mutations. 1550 82

Hypoxanthine-guanine phosphoribosyl transferase (HPRT) deficiency is an X-linked defect of purine metabolism. Clinical manifestations are usually related to the degree of enzyme deficiency; complete HPRT deficiency (Lesh-Nyhan Syndrome) presenting with severe neurological or renal symptoms, or partial HPRT deficiency (Kelley-Seegmiller syndrome) manifesting as a gout-urolithiasis syndrome. We report a case of partial HPRT deficiency presenting as chronic tophaceous gout, mental retardation, nephrolithiasis and family history suggestive of X-linked inheritance, for its rarity.
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PMID:Partial HPRT deficiency (Kelley-Seegmiller syndrome). 1664 40

Arts syndrome is an X-linked disorder characterized by mental retardation, early-onset hypotonia, ataxia, delayed motor development, hearing impairment, and optic atrophy. Linkage analysis in a Dutch family and an Australian family suggested that the candidate gene maps to Xq22.1-q24. Oligonucleotide microarray expression profiling of fibroblasts from two probands of the Dutch family revealed reduced expression levels of the phosphoribosyl pyrophosphate synthetase 1 gene (PRPS1). Subsequent sequencing of PRPS1 led to the identification of two different missense mutations, c.455T-->C (p.L152P) in the Dutch family and c.398A-->C (p.Q133P) in the Australian family. Both mutations result in a loss of phosphoribosyl pyrophosphate synthetase 1 activity, as was shown in silico by molecular modeling and was shown in vitro by phosphoribosyl pyrophosphate synthetase activity assays in erythrocytes and fibroblasts from patients. This is in contrast to the gain-of-function mutations in PRPS1 that were identified previously in PRPS-related gout. The loss-of-function mutations of PRPS1 likely result in impaired purine biosynthesis, which is supported by the undetectable hypoxanthine in urine and the reduced uric acid levels in serum from patients. To replenish low levels of purines, treatment with S-adenosylmethionine theoretically could have therapeutic efficacy, and a clinical trial involving the two affected Australian brothers is currently underway.
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PMID:Arts syndrome is caused by loss-of-function mutations in PRPS1. 1770 96

PRPP(phosphoribosyl pyrophosphate) synthetase catalyzes the formation of PRPP from ATP and ribose 5-phosphate. Human PRPP synthetase exists as heterogeneous aggregates composed of the 34kDa catalytic subunits (PRSI and PRSII) and other 39kDa and 41kDa components designated PRPP synthetase-associated protein (PAP39 and PAP41). A syndrome of increased activity of PRPP synthetase, an X-linked dominant-inherited disorder, is one of the models of gout caused by increased production of uric acid. By now, around twenty cases have been reported over the world. Two different molecular mechanisms underlie this syndrome: (1) point mutation in the gene coding the primary structure of PRPP synthetase causes the substitution of an amino acid residue and, consequently, the regulatory defects, those are resistant traits to allosteric nucleotide feedback inhibition; (2) increased transcription of PRPP synthetase mRNA causes overproduction of this enzyme protein. The mechanism producing increased mRNA is, however, not elucidated. The Japanese case has been found to be caused by the second mechanism.
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PMID:[Increased activity of PRPP synthetase]. 1840 17

Hyperuricemia depends on the balance of endogenous production and renal excretion of uric acid. Transporters for urate are located in the proximal tubule where uric acid is secreted and extensively reabsorbed: secretion is principally ensured by the highly variable ABCG2 gene. Enzyme hypoxanthine-guanine phosphoribosyltransferase (HPRT) plays a central role in purine metabolism and its deficiency is an X-linked inherited metabolic disorder associated with clinical manifestations of purine overproduction. Here we report the case of a middle-aged man with severe chronic tophaceous gout with a poor response to allopurinol and requiring repeated surgical intervention. We identified the causal mutations in the HPRT1 gene, variant c.481G>T (p.A161S), and in the crucial urate transporter ABCG2, a heterozygous variant c.421C>A (p.Q141K). This case shows the value of an analysis of the genetic background of serum uric acid.
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PMID:Genetic background of uric acid metabolism in a patient with severe chronic tophaceous gout. 2728 85

Lesch-Nyhan syndrome (LNS) is a rare X-linked disorder caused by mutations in HPRT1, an important enzyme in the purine salvage pathway. Symptoms of LNS include dystonia, gout, intellectual disability, and self-mutilation. Despite having been characterized over 50 years ago, it remains unclear precisely how deficits in hypoxanthine and guanine recycling can lead to such a profound neurological phenotype. Several studies have proposed different hypotheses regarding the etiology of this disease, and several treatments have been tried in patients, though none have led to a satisfactory explanation of the disease. New technologies such as next-generation sequencing, optogenetics, genome editing, and induced pluripotent stem cells provide a unique opportunity to map the precise sequential pathways leading from genotype to phenotype.
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PMID:Lesch-Nyhan Syndrome: Models, Theories, and Therapies. 2792 Jun 33


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