Lesch-Nyhan disease in two families from Chiloé Island with mutations in the HPRT1 gene.

Lesch-Nyhan disease (LND) is a rare X-linked inherited neurogenetic disorder of purine metabolism in which the enzyme, hypoxanthine-guanine phosphoribosyltransferase (HGprt) is defective. The authors report two independent point mutations leading to splicing errors: IVS 2 +1G>A, c.134 +1G>A, and IVS 3 +1G>A, c.318 +1G>A in the hypoxanthine-phosphoribosyltransferase1 (HPRT1) gene which result in exclusion of exon 2 and exon 3 respectively, in the HGprt enzyme protein from different members of two Chiloé Island families. Molecular analysis has revealed the heterogeneity of genetic mutation of the HPRT1 gene responsible for the HGprt deficiency. It allows fast, accurate carrier detection and genetic counseling.

HPRTYale proposed as a pathogenic variant for Lesch-Nyhan syndrome: a case report.

Lesch-Nyhan syndrome (LNS) is an X-linked recessive disorder caused by a deficiency of hypoxanthine-guanine phosphoribosyltransferase (HPRT), an enzyme encoded by the HPRT1 gene. The classic disease phenotype described by Lesch and Nyhan in 1964 includes hyperuricemia, mental retardation, severe motor deficiency, and recurring self-mutilation. Here, we report the case of a family with 4 affected males and several female obligate carriers. In 1989, Fujimori et al. reported on a patient diagnosed with LNS who had an HPRT variant thereafter codenamed HPRTYale. The same patient was studied by Wilson et al. in 1986, who found no detectable HPRT enzymatic activity, even though normal HPRT mRNA and protein levels were observed. Disease severity is closely related to residual enzymatic activity, which fits the phenotype presented for this previously reported case, as well as for the patients we report on herein. As it has been reported in only one patient, this mutation is still considered a variant of unknown significance. The HPRTYale mutation is a G>C transversion that leads to a different amino acid with different biochemical properties at position 71, potentially causing the major lack of function. To evaluate the impact of this variant, we used the PolyPhen-2 software, which classified it as possibly damaging. Furthermore, the frequency of this mutant allele is likely extremely rare, since it has only been reported on twice, and a population frequency is not yet available. In conclusion, we propose that the HPRTYale variant is pathogenic, and should be included on lab reports hereafter.

Hypoxanthine-guanine phosphoribosyltransferase deficiency in a patient with a Madrid II mutation.

The hypoxanthine-guanine phosphoribosyltransferase deficiency is an inborn error of purine metabolism, linked to the X chromosome. The clinical phenotypes associated with HPRT deficiency varied according to the level of enzyme deficiency, with a large spectrum of neurologic features like self-injurious behaviour in patients with complete deficiency. We report a 20-year-old man who had asymmetric polyarthritis, tophi, hyperuricemia, nephrolithiasis and mild neurologic symptoms with undetectable levels of HPRT activity in lysed erythrocytes. The genetic study identified the c.143G>A mutation in exon 3, GAA CGT (CTT>GAA CAT CTT (48arg>his). The presence of gouty arthropathy and chronic hyperuricemia in a young patient with neurological symptoms, suggests HPRT deficiency for which it is necessary its enzyme and molecular determination.

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.

Molecular analysis of HPRT1(+) somatic cell hybrids derived from a carrier of an HPRT1 mutation responsible for Lesch-Nyhan syndrome.

Heterozygous carriers of HPRT1 mutations responsible for Lesch-Nyhan syndrome can be detected by analysis of somatic cell hybrids derived from peripheral blood lymphocytes and Hprt1-negative cells of rodent origin followed by selection in culture medium containing hypoxanthine, aminopterine, and thymidine (HAT). The parental origin of the X chromosome containing the normal HPRT1 allele in HPRT1(+) hybrid cell lines can be determined by molecular haplotyping attributable to highly polymorphic X-linked markers. We used this procedure to study a presumed carrier whose paternal active X chromosome always segregated in the cell hybrids derived from her. Conversely, her maternal X chromosome was systematically absent in most cell hybrids, or when present, it was inactive and coexisted with an active, paternal X chromosome. These results clearly demonstrated that the proband was a heterozygous carrier of a mutation responsible for HPRT1 deficiency.

Uma nova estratégia para o diagnóstico de mulheres portadoras de mutações que causam a síndrome de LESCH-NYHAN

A síndrome de Lesch-Nyhan é uma entidade clínica que apresenta um padrão de herança recessivo ligado ao cromossomo X. Pertence ao grupo dos erros inatos do metabolismo e é originada por uma deficiência absoluta da enzima hipoxantina-guanina fosforibosiltransferase (HPRT1; EC 2.4.2.8). Mulheres heterozigotas para mutações HPRT1 que causam a síndrome de Lesch-Nyhan podem ser detectadas mediante análises moleculares de híbridos celulares somáticos derivados da fusão de Iinfócitos de sangue periférico e células Hprt-negativas provenientes de roedor com a subseqüente seleção em meio de cultura contendo hipoxantina, aminopterina e timidina (HAT). A origem parental do cromossomo X contendo o alelo HPRT1 normal em linhagens celulares híbridas HPRT1 + pode ser determinada por haplótipos moleculares demonstrados por marcadores altamente polimórficos ligados ao cromossomo X. Esta metodologia foi utilizada para estudar uma possível heterozigota cujo cromossomo X paterno ativo esta sempre presente nas linhagens celulares derivadas dela. Contrariamente, o cromossomo X materno esteve sistematicamente ausente na maioria dos híbridos, e quando presente, estava inativo coexistindo com um X paterno ativo. Sub-clones sem o X paterno ativo e contendo o X materno inativo, não apresentaram atividade HPRT1 quando tratados com 5-aza-citidina. A ausência de transcrito do HPRT1 após o tratamento foi comprovada mediante RT-PCR. Estes resultados claramente demonstraram que a probanda é portadora de uma mutação responsável pela deficiência de HPRT1

Lesch-Nyhan syndrome is a recessive X-Iinked metabolic disorder resulting from absolute deficiency of the enzyme hypoxanthine/guanine phosphoribosy/transferase (HPRT1; EC 2.4.2.8). Heterozygous carriers of HPRT1 mutations responsible for Lesch-Nyhan syndrome can be detected by analysis of somatic cell hybrids derived from peripheral blood Iymphocytes and Hprt-negative cells of rodent origin followed by selection in culture medium containing hypoxanthine, aminopterine, and thymidine (HAT). The parental origin of the X chromosome containing the normal HPRT1 allele in HPRT1 + hybrid cell lines can be determined by molecular haplotyping attributable to highly polymorphic X-Iinked markers. We used this procedure to study a presumed carrier whose paternal active X chromosome always segregated in the cell hybrids derived from her. Conversely, her maternal X chromosome was systematically absent in most of cell hybrids, or when present, it was inactive and coexisted with an active, paternal X chromosome. Sub-clones lacking the paternal, active X chromosome and containing the X inactive maternal chromosome were unable to reactivate the HPRT1 locus following treatment with 5-aza-eytidine. HPRT1 transcripts were found to be absent with RT -PCR. These results c1early demonstrated that the proband was a heterozygous carrier of a mutation responsible for HPRT1 deficiency

An unexpected affected female patient in a classical Lesch-Nyhan family.

Lesch-Nyhan disease is a genetic disorder of purine metabolism caused by defective activity of the enzyme hypoxanthine-guanine phosphoribosyl transferase (HPRT), resulting from mutation in the corresponding gene on the long arm of the X chromosome (Xq26). The classical phenotype, which includes spasticity, involuntary movements, developmental disability, and self-injurious behavior, occurs exclusively in males, while heterozygous, carrier females are clinically normal. We analyzed an Argentine family in which there were male and female siblings with clinically identical classic features of Lesch-Nyhan disease. The mother and an older daughter were carriers and had normal phenotypes. We identified the HPRT mutation in the family. It is a C --> T transition at position 508 of the cDNA (c.508 C --> T) that changes the CGA codon for Arg(169) to the TGA stop codon (R169X). The female patient was karyotypically normal and heterozygous for the mutation. She inherited the HPRT mutation from her mother, but she also had unexpected nonrandom inactivation of the paternal X chromosome carrying the normal HPRT gene. This additional genetic alteration is the cause of the clinical expression of disease in this female patient.

Identification of a new lesch syndrome mutation (HPRT BRASIL) and analysis of pontentially heterozygous females

The mutation in the hypoxanthine-guanine phosphoribosyltransfere (HPRT) gene has been determined in two brothers affected with Lesch-Nyhan syndrome. Female members of the family who are at risk for being heterozygous carriers of the HPRT mutation were also studied to determine whether they carry the mutation. DNA sequencing revealed that the boys' mother heterozygous for the mutation in her somatic cells, but that three maternal aunts are not heterozygous. Such carrier information is important for the future pregnancy plans of at-risk females. The mutation, an A_T transversion at cDNA base 590 (590 A_T), results in an amino acid change of glutamic acid to valine at codon 197, and has not been reported previously in a Lesch-Nyhan syndrome male. This mutation is designated HPRT.

Identification of a new Lesch-Nyhan syndrome mutation (HPRTBrasil) and analysis of potentially heterozygous females.

The mutation in the hypoxanthine-guanine phosphoribosyltransferase (HPRT) gene has been determined in two brothers affected with Lesch-Nyhan syndrome. Female members of the family who are at risk for being heterozygous carriers of the HPRT mutation were also studied to determine whether they carry the mutation. DNA sequencing revealed that the boys' mother is heterozygous for the mutation in her somatic cells, but that three maternal aunts are not heterozygous. Such carrier information is important for the future pregnancy plans of at-risk females. The mutation, an A-->T transversion at cDNA base 590 (590A-->T), results in an amino acid change of glutamic acid to valine at codon 197, and has not been reported previously in a Lesch-Nyhan syndrome male. This mutation is designated HPRTBrasil.

Síndrome de Lesch-Nyhan incompleto : comunicación del primer caso argentino / Incomplete Lesch-Nyhan syndrome : communication of first case argentinian

El síndrome de Lesch-Nyhan es una infrecuente gota hereditaria vinculada al déficit virtualmente completo de la enzima hipoxantina guanina fosforribosil transferasa (HGFT) existiendo ocasionalmente déficit parciales, que se diferencian de las formas completas por presentar manifestaciones neuropsiquiátricas menores. Es nuestro objetivo presentar al que en nuestro conocimiento es el primer paciente argentino portador del síndrome de Lesh-Nyhan incompleto o de Kelley-Seegmiller. Paciente varón de 38 años con historia familiar de gota e insuficiencia renal que desarrolla una severa artritis gotosa tofácea de rápida evolución y déficit intelectual. Los análisis de laboratorio de rutina mostraron una marcada hiperuricemia y excesiva excreción de ácido úrico con una función renal conservada. La determinación de la actividad enzimática de la HGFT se halló francamente disminuida.

Síndrome de Lesch-Nyhan incompleto : comunicación del primer caso argentino / Incomplete Lesch-Nyhan syndrome : communication of first case argentinian

El síndrome de Lesch-Nyhan es una infrecuente gota hereditaria vinculada al déficit virtualmente completo de la enzima hipoxantina guanina fosforribosil transferasa (HGFT) existiendo ocasionalmente déficit parciales, que se diferencian de las formas completas por presentar manifestaciones neuropsiquiátricas menores. Es nuestro objetivo presentar al que en nuestro conocimiento es el primer paciente argentino portador del síndrome de Lesh-Nyhan incompleto o de Kelley-Seegmiller. Paciente varón de 38 años con historia familiar de gota e insuficiencia renal que desarrolla una severa artritis gotosa tofácea de rápida evolución y déficit intelectual. Los análisis de laboratorio de rutina mostraron una marcada hiperuricemia y excesiva excreción de ácido úrico con una función renal conservada. La determinación de la actividad enzimática de la HGFT se halló francamente disminuida. (AU)

Aspectos clínicos y bioquímicos del síndrome de Lesch-Nyhan

El síndrome de Lesch-Nyhan es una enfermedad genética ligada al cromosoma X, originada por un defecto en el gen que codifica la hipoxantia guanina fosforribosiltransferasa (HGPRT). Esta enzima participa en la recuperación de la guanina e hipoxantina. La deficiencia enzemática conlleva una acumulación exagerada del ácido úrico. La deficiencia total o casi total de la enzima, produce el síndrome de Lesch-Nyhan, el cual se caracteriza por hiperruricemia, hiperaciduria, coreoatetosis, hiperreflexia, retardo mental y autoagresividad. La deficiencia parcial de la enzima ocasiona artritis gotosa y nefrolitiasis sin daño neurológico.

Enfermedad de Lesch-Nyhan / Lesch-Nyhan disease

Se presenta un caso de Enfermedad de Lesch-Nyhan típico, cuyo diagnóstico fue confirmado a través de técnicas de crecimiento celular diferencial. Esta técnica permitió también establecer la condición de portadora en la madre y una de las tías en la que se realizó el diagnóstico prenatal de un nuevo caso. Se revisan algunos aspectos clínicos, metabólicos y terapéuticos de interés, enfatizando la importancia de los estudios diagnósticos específicos para el consejo genético adecuado de familias con esta rara pero grave enfermedad