Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: UMLS:C0025362 (mental retardation)
 15,878 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Lesch-Nyhan disease (LND) is an inborn error of purine metabolism caused by defective activity of the enzyme hypoxanthine guanine phosphoribosyl transferase (HPRT, EC 2.4.2.8), resulting from mutation in the corresponding gene on the long arm of the X chromosome (Xq26). The classic phenotype occurs almost exclusively in males and is characterized by hyperuricemia, mental retardation, severe dystonia, and self-injurious behavior. Heterozygous carrier females are usually clinically normal. However, a small number of clinically affected females have been described. In all previous cases there was a mutation in one HPRT allele and non-random inactivation of the X chromosome carrying the normal HPRT gene. We have analyzed a female MZ twin pair discordant for Lesch-Nyhan disease. The mother and both twins are heterozygous carriers of a HPRT splicing mutation (IVS8 + 4A > G; c.609 + 4A > G) and all three express the mutant allele at similar frequencies in peripheral blood T cells. The mother and one sister are clinically normal. In the affected twin, the clinical phenotype is classical for Lesch-Nyhan disease, despite the fact that HPRT activity in the blood was also normal. X inactivation analysis showed a skewed pattern in the fibroblasts of the affected twin sister, with the X chromosome carrying the normal HPRT allele preferentially inactivated. As in many other reported cases of X-linked diseases, the discordant phenotype of the two monozygous twin sisters suggests that the process responsible for monozygotic twinning can trigger skewed X inactivation.
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PMID:Lesch-Nyhan disease in a female with a clinically normal monozygotic twin. 1586 83

Lesch-Nyhan disease (LND) is a rare disorder caused by a defect of an enzyme in the purine salvage pathway, hypoxanthine phosphoribosyl transferase (HPRT). It is still unknown how the metabolic defect translates into the complex neuropsychiatric phenotype characterized by self-injurious behavior, dystonia and mental retardation. There are abnormalities in purine and pyrimidine nucleotide content in HPRT-deficient cells. We hypothesized that altered nucleotide concentrations in HPRT deficiency change G-protein-mediated signal transduction. Therefore, our original study aim was to examine the high-affinity GTPase activity of G-proteins in membranes from primary human skin and immortalized mouse skin fibroblasts, rat B103 neuroblastoma cells and mouse Neuro-2a neuroblastoma cells. Unexpectedly, in membranes from human fibroblasts, B103- and Neuro-2a cells, V(max) of low-affinity nucleoside 5'-triphosphatase (NTPase) activities was decreased up to 7-fold in HPRT deficiency. In contrast, in membranes from mouse fibroblasts, HPRT deficiency increased NTPase activity up to 4-fold. The various systems analyzed differed from each other in terms of K(m) values for NTPs, absolute V(max) values and K(i) values for nucleoside 5'-[beta,gamma-imido]triphosphates. Our data show that altered membrane NTPase activity is a biochemical hallmark of HPRT deficiency, but species and cell-type differences have to be considered. Thus, future studies on biochemical changes in LND should be conducted in parallel in several HPRT-deficient systems.
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PMID:Altered membrane NTPase activity in Lesch-Nyhan disease fibroblasts: comparison with HPRT knockout mice and HPRT-deficient cell lines. 1593 74

Lesch-Nyhan syndrome (LNS), first described in 1964 by Lesch and Nyhan, is a rare X-linked genetic disorder involving (near) absence of the enzyme hypoxanthine-guanine phosphoribosyl transferase (HPRT). It occurs in 1:100,000 to 380,000 live births (1, 2). The deficiency of HPRT activity leads to an excessive uric acid production resulting in neurological, renal and musculoskeletal manifestations. Death usually occurs in the second or third decade from infection or renal failure. Clinical presentation is characterized by mental retardation, choreoathetosis, spasticity, hyperuricemia and cerebral palsy. A characteristic feature of LNS is the appearance of intractable self-injurious behaviour (SIB), usually in the form of severe lip and finger biting, gouging of eyes, face scratching and head banging requiring extreme management techniques such as the application of restraints and or extraction of teeth at an early age. In this case report a unique approach of SIB in LNS is presented.
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PMID:Self-mutilation behaviour in Lesch-Nyhan syndrome. 1613 97

Self-injury is a defining feature of lesch-nyhan disease (LND) but does not occur in the less severely affected Lesch-Nyhan variants (LNV). The aim of this study was to quantify behavioral and emotional abnormalities in LND and LNV. Thirty-nine informants rated 22 patients with LND (21 males, 1 female), 11 males with LNV, and 11 healthy controls (HC; 10 males, 1 female) using two well-validated rating scales. The age of patients with LND ranged from 12 years 7 months to 38 years 3 months (mean 22 y 11 mo; sd 7 y 8 mo), whereas the age range of those with LNV was 12 years 9 months to 65 years (mean 30 y 7 mo; sd 15 y 2 mo), and the healthy controls were aged 12 years 4 months to 31 years 3 months (mean 17 y 10 mo; sd 5 y 7 mo). Behavioral ratings were based on the Child Behavior Checklist and the American Association On Mental Retardation's Adaptive Behavior Scale--Residential And Community, 2nd edition. Statistical analyses revealed that patients with LND showed severe self-injury together with problematic aggression, anxious-depressed symptoms, distractibility, motor stereotypes, and disturbing interpersonal behaviors. Patients with LNV were rated as being intermediate between the HC and LND groups on all behavior scales. Although the LNV group did not differ from hcs on most scales, their reported attention problems were as severe as those found in LND. We conclude that self-injurious and aggressive behaviors are nearly universal and that other behavioral abnormalities are common in LND. Although patients with LNV typically do not self-injure or display severe aggression, attention problems are common and a few patients demonstrate other behavioral anomalies.
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PMID:Behavioral aspects of Lesch-Nyhan disease and its variants. 1617 10

Defect of the purine salvage enzyme, hypoxanthine phosphoribosyl transferase (HPRT), results in Lesch-Nyhan disease (LND). It is unknown how the metabolic defect translates into the severe neuropsychiatric phenotype characterized by self-injurious behavior, dystonia and mental retardation. There are abnormalities in GTP, UTP and CTP concentrations in HPRT-deficient cells. Moreover, GTP, ITP, XTP, UTP and CTP differentially support Gs-protein-mediated adenylyl cyclase (AC) activation. Based on these findings we hypothesized that abnormal AC regulation may constitute the missing link between HPRT deficiency and the neuropsychiatric symptoms in LND. To test this hypothesis, we studied AC activity in membranes from primary human skin and immortalized mouse skin fibroblasts, mouse Neuro-2a neuroblastoma cells and rat B103 neuroblastoma cells. In B103 control membranes, GTP, ITP, XTP and UTP exhibited profound stimulatory effects on basal AC activity that approached the effects of hydrolysis-resistant nucleotide analogs. In HPRT- membranes, the stimulatory effects of GTP, ITP, XTP and UTP were strongly reduced. Similarly, in human and mouse skin fibroblast membranes we also observed a decrease in GTP-stimulated AC activity in HPRT-deficient cells compared with the respective controls. In mouse Neuro-2a neuroblastoma membranes, AC activity in the presence of GTP was below the detection limit of the assay. We discuss several possibilities to explain the abnormalities in AC regulation in HPRT deficiency that encompass various species and cell types.
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PMID:Decreased GTP-stimulated adenylyl cyclase activity in HPRT-deficient human and mouse fibroblast and rat B103 neuroblastoma cell membranes. 1633 32

Lesch-Nyhan disease (LND) is caused by deficiency of the purine salvage enzyme hypoxanthine-guanine phosphoribosyltransferase (HPRT). Affected individuals exhibit over-production of uric acid, along with a characteristic neurobehavioural syndrome that includes mental retardation, recurrent self-injurious behaviour and motor disability. Prior studies involving relatively small numbers of patients have provided different conclusions on the nature of the motor disorder. The current study includes the results of a multi-centre international prospective study of the motor disorder in the largest cohort of patients studied to date. A total of 44 patients ranging from 2 to 38 years presented a characteristic motor syndrome that involved severe action dystonia superimposed on baseline hypotonia. Although some patients also displayed other extrapyramidal or pyramidal signs, these were always less prominent than dystonia. These results are compared with a comprehensive review of 122 prior reports that included a total of 254 patients. Explanations for the differing observations available in the literature are provided, along with a summary of how the motor disorder of LND relates to current understanding of its pathophysiology involving the basal ganglia.
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PMID:Delineation of the motor disorder of Lesch-Nyhan disease. 1654 99

Lesch-Nyhan syndrome (LNS) is an X-linked genetic disorder resulting in hyperuricemia, choreoathetosis, mental retardation, and self-injurious behavior. It is caused by loss of activity of the ubiquitous enzyme hypoxanthine-guanine-phosphoribosyltransferase (HPRT). The biochemical analysis of residual HPRT activity in patients' red blood cells is the first step in LNS diagnosis, and it precedes molecular study to discover the specific mutation. Unfortunately, biochemical diagnosis of healthy carriers is difficult because HPRT enzymatic activity in blood cells is similar in LNS carriers and in healthy people; genetic tests can help reveal mutations at the genomic or cDNA level, whereas gross deletions involving the first or last exons of HPRT gene are not detectable. Until now, a test based on 6-thioguanine-resistant phenotype of HPRT mutant cells from LNS patients is the only method accepted for the diagnosis of any kind of mutation in carriers. In this work, we introduce a new approach to identify carriers of large deletions in HPRT gene using real-time PCR. Results were validated in a blinded manner with a linkage study and with results obtained in Italian families previously analyzed with selective medium test. Real-time PCR analysis clearly confirmed the results obtained by selective medium; linkage data strengthened real time results, allowing us to follow the allele with the mutated HPRT through the family pedigree. We hope that the real-time PCR approach will provide a useful and reliable method to diagnose LNS carriers of large deletions in HPRT gene.
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PMID:Real-time PCR and linkage studies to identify carriers presenting HPRT deleted gene. 1722 73

Lesch-Nyhan syndrome is a very rare X-linked recessive disorder characterized by mental retardation, spasticity resembling cerebral palsy, choreo-athetosis, self-mutilation and hyperuricemia. Self-mutilative behavior is a hallmark of the disease. Hyperuricemia leads to hyperuricuria and uric acid nephrolithiasis. The underlying defect is a deficiency of hypoxanthine-guanine-phosphoribosyl transferase. We report on a 7-year-old boy with Lesch-Nyhan syndrome, lacking self-mutilative behavior, who was erroneously diagnosed as having athetotic cerebral palsy. He also had no renal stones; hyperechoic renal medullary pyramids were the only renal abnormality detected and were sonographically indistinguishable from medullary nephrocalcinosis.
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PMID:Rare variant of Lesch-Nyhan syndrome without self-mutilation or nephrolithiasis. 1768 Feb 74

The genetic deficiency of hypoxanthine-guanine phosphoribosyltransferase (HPRT), located on the X chromosome, causes a severe neurological disorder in man, known as Lesch-Nyhan disease (LND). The enzyme HPRT is part of the savage pathway of purine biosynthesis and catalyzes the conversion of hypoxanthine and guanine to their respective nucleotides, IMP and GMP. HPRT deficiency is associated with a relatively selective dysfunction of brain dopamine systems. Several metabolites that accumulate in the patients (phosphoribosylpyrophosphate (PRPP), hypoxanthine, guanine, xanthine, and Z-nucleotides) have been proposed as toxic agents in LND. Some authors have pointed that Z-riboside, derived from the accumulation of ZMP, could be the toxic metabolite in LND. However, the available experimental data support a better hypothesis. I suggest that ZMP (and not Z-riboside) is the key toxic metabolite in LND. ZMP is an inhibitor of the bifunctional enzyme adenylosuccinate lyase, and a deficiency of this enzyme causes psychomotor and mental retardation in humans. Moreover, it has been reported that ZMP inhibits mitochondrial oxidative phosphorylation and induces apoptosis in certain cell types. ZMP is also an activator of the AMP-activated protein kinase (AMPK), a homeostatic regulator of energy levels in the cell. The AMPK has been implicated in the regulation of cell viability, catecholamine biosynthesis and cell structure. I propose that accumulation of ZMP will induce a pleiotropic effect in the brain by (1) a direct inhibition of mitochondrial respiration and the bifunctional enzyme adenylosuccinate lyase, and (2) a sustained activation of the AMPK which in turns would reduce cell viability, decrease dopamine synthesis, and alters cell morphology. In addition, a mechanism to explain the accumulation of ZMP in LND is presented. The knowledge of the toxic metabolite, and the way it acts, would help to design a better therapy.
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PMID:Is ZMP the toxic metabolite in Lesch-Nyhan disease? 1871 Jul 92

Lesch-Nyhan syndrome, a rare inborn error of metabolism, is characterized by mental retardation and self-destructive behavior resulting in self-mutilation through biting and scratching. It is a rare anomaly consisting of deficiency in the production of hypoxanthine phosphoribosyltransferase that leads to the overproduction of purine and accumulation of uric acid. No medical treatment exists to alleviate the symptoms of self-mutilation where direct dental intervention is the only way these behavior can be affected. A unique case of this type affecting a 6-year-old male child is reported.
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PMID:Lesch-Nyhan syndrome: a case report. 1897 38


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