A broad spectrum of genomic changes in latinamerican patients with EXT1/EXT2-CDG.

Multiple osteochondromatosis (MO), or EXT1/EXT2-CDG, is an autosomal dominant O-linked glycosylation disorder characterized by the formation of multiple cartilage-capped tumors (osteochondromas). In contrast, solitary osteochondroma (SO) is a non-hereditary condition. EXT1 and EXT2, are tumor suppressor genes that encode glycosyltransferases involved in heparan sulfate elongation. We present the clinical and molecular analysis of 33 unrelated Latin American patients (27 MO and 6 SO). Sixty-three percent of all MO cases presented severe phenotype and two malignant transformations to chondrosarcoma (7%). We found the mutant allele in 78% of MO patients. Ten mutations were novel. The disease-causing mutations remained unknown in 22% of the MO patients and in all SO patients. No second mutational hit was detected in the DNA of the secondary chondrosarcoma from a patient who carried a nonsense EXT1 mutation. Neither EXT1 nor EXT2 protein could be detected in this sample. This is the first Latin American research program on EXT1/EXT2-CDG.

An integrated strategy for the diagnosis of neuronal ceroid lipofuscinosis types 1 (CLN1) and 2 (CLN2) in eleven Latin American patients.

The neuronal ceroid lipofuscinoses (NCLs) are a family of progressive neurodegenerative diseases that are characterized by the cellular accumulation of ceroid lipofuscin-like bodies. NCL type 1 (CLN1) and type 2 (CLN2) are caused by deficiencies of the lysosomal enzymes palmitoyl-protein thioesterase 1 (PPT-1) and tripeptidyl peptidase 1 (TPP-1), respectively. In this study, 118 Latin American patients were examined for NCL using an integrated multidisciplinary program. This revealed two patients affected by CLN1 and nine by CLN2. Both CLN1 patients had a juvenile-onset phenotype with mutation studies of one patient demonstrating the known mutation p.Arg151X and a novel mutation in intron 3, c.363-3T>G. Six of the CLN2 patients presented with the 'classical' late-infantile phenotype. The remaining three patients, who were siblings, presented with a 'protracted' phenotype and had a higher level of residual TPP-1 activity than the 'classical' CLN2 patients. Genotype analysis of the TPP1 gene in the 'classical' CLN2 patients showed the presence of the known mutation p.Arg208X and the novel mutations p.Leu104X, p.Asp276Val, and p.Ala453Val. The siblings with the 'protracted' phenotype were heterozygous for two known TPP1 mutations, p.Gln66X and c.887-10A>G. This multidisciplinary program is also being used to diagnose other NCL types.

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.

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.

Genetic polymorphism of thiopurine S-methyltransferase in Argentina.

BACKGROUND: Thiopurine methyltransferase (TPMT) catalyses the S-methylation of 6-thiopurine drugs, which are commonly used in the treatment of autoimmune diseases, leukaemia and organ transplantation. TPMT activity is polymorphic as a result of gene mutations. Ethnic variations in phenotype and genotype have been identified in previous population studies, but no information was available within Latin-American populations. AIM: To establish the genetic polymorphism of TPMT in an Argentine population. METHODS: TPMT enzymatic activity of 147 healthy Argentine subjects was measured using a high-performance liquid chromatography method. The genotyping assay for nine defective alleles (TPMT*2 - *8) was based on restriction fragment length polymorphism polymerase chain reaction and allele-specific polymerase chain reaction methods. RESULTS: All subjects had detectable TPMT activity. Twelve individuals with low to intermediate activity were heterozygous for one of the mutant alleles: nine were TPMT*1/*3A, two TPMT*1/*2 and one TPMT*1/*4. All examined subjects with normal activity had wild-type genotype (TPMT*1/*1). CONCLUSION: Variant TPMT alleles were present in 8.2% of the examined subjects, which is in accordance with other studies. The frequency of TPMT*3A, TPMT*2 and TPMT*4 was 3.1%, 0.7% and 0.3%, respectively. TPMT*3A was the most prevalent allele, which is in accordance with results from Caucasian populations. This study provides the first analysis of TPMT activity and allele frequency distribution in Argentina, South America.

Deficiencia de la 3-hidroxi-3-metilglutaril coenzima-A liasa como causa de severo daño neurologico / 3-hydroxy-3-methylglutaryl-coenzyme A lyase deficiency as a cause of severe neurological damage

Se trata de la primera descripción en Argentina de una 3-hidroxi-3-metilglutárica aciduria (HMG-Aciduria), defecto genético de la cetogénesis hepática y en el último paso catabólico de la leucina. A la edad de 4 meses, el paciente debutó con un grave cuadro clínico evocador de un Síndrome de Reye; la ausencia de cambios en los aminoácidos séricos y urinários, como asimismo el no incremento en la excreción de los ácidos p-hidroxifenólicos y la presencia de acidosis metabólica sin cetosis, orientaron hacia defecto cetogénico. Un perfil anormal de ácidos orgánicos urinarios, detectado por cromatografía en capa delgada y luego caracterizado y cuantificado por cromatografía de gas-espectrometría de masa, demostró un muy marcado incremento de los metabolitos típicos de la HMG-Aciduria: 3-hidroxi-3-metilglutárico, 3 metilglutacónico, 3-metilglutárico y el 3-hidroxisovalérico. La actividad de la 3-hidroxi-3-metilglutaril-CoA Liasa en leucocitos y fibroblastos cultivados de una biopsia de piel del paciente, señaló una ausencia total en los primero y entre un 2-5% de los valores controles en los segundos. La terapia aplicada en base a una dieta restrictiva en leucina o hipoproteica, hipograsa y la administración continua de L-carnitina no logró mayores efecto sobre el cuadro neurológico ya evidenciado a partir de la primera crisis. La resonancia magnética del cerebro, realizada al año y 8 meses de edad, mostró en T1 imágenes sugestivas de una marcada atrofia cerebral y en T2 imágenes hiperintensas predominantes en la región frontal derecha y parietales posteriores y de tipo puntiforme en los ganglios basales, en particular en la cabeza de ambos núcleos caudados. Estos hallazgos eran compatibles con gliosis y/o desmielinización de la sustancia blanca y necrosis neuronal de la sustancia gris, objetivaciones en probable correlato al profundo retardo sicomotor convulsiones, microcefalia e hipotonía generalizada del niño e interpretado más bien como de tipo secuelar que como otra variante fenotípica de la enfermedad. De allí el acento en señalar la importancia de la alta presunción clínica y de la precocidad del tratamiento inicial sindrómico en la emergencia metabólica (AU)

Deficiencia de la 3-hidroxi-3-metilglutaril coenzima-A liasa como causa de severo daño neurologico / 3-hydroxy-3-methylglutaryl-coenzyme A lyase deficiency as a cause of severe neurological damage

Se trata de la primera descripción en Argentina de una 3-hidroxi-3-metilglutárica aciduria (HMG-Aciduria), defecto genético de la cetogénesis hepática y en el último paso catabólico de la leucina. A la edad de 4 meses, el paciente debutó con un grave cuadro clínico evocador de un Síndrome de Reye; la ausencia de cambios en los aminoácidos séricos y urinários, como asimismo el no incremento en la excreción de los ácidos p-hidroxifenólicos y la presencia de acidosis metabólica sin cetosis, orientaron hacia defecto cetogénico. Un perfil anormal de ácidos orgánicos urinarios, detectado por cromatografía en capa delgada y luego caracterizado y cuantificado por cromatografía de gas-espectrometría de masa, demostró un muy marcado incremento de los metabolitos típicos de la HMG-Aciduria: 3-hidroxi-3-metilglutárico, 3 metilglutacónico, 3-metilglutárico y el 3-hidroxisovalérico. La actividad de la 3-hidroxi-3-metilglutaril-CoA Liasa en leucocitos y fibroblastos cultivados de una biopsia de piel del paciente, señaló una ausencia total en los primero y entre un 2-5% de los valores controles en los segundos. La terapia aplicada en base a una dieta restrictiva en leucina o hipoproteica, hipograsa y la administración continua de L-carnitina no logró mayores efecto sobre el cuadro neurológico ya evidenciado a partir de la primera crisis. La resonancia magnética del cerebro, realizada al año y 8 meses de edad, mostró en T1 imágenes sugestivas de una marcada atrofia cerebral y en T2 imágenes hiperintensas predominantes en la región frontal derecha y parietales posteriores y de tipo puntiforme en los ganglios basales, en particular en la cabeza de ambos núcleos caudados. Estos hallazgos eran compatibles con gliosis y/o desmielinización de la sustancia blanca y necrosis neuronal de la sustancia gris, objetivaciones en probable correlato al profundo retardo sicomotor convulsiones, microcefalia e hipotonía generalizada del niño e interpretado más bien como de tipo secuelar que como otra variante fenotípica de la enfermedad. De allí el acento en señalar la importancia de la alta presunción clínica y de la precocidad del tratamiento inicial sindrómico en la emergencia metabólica