Analysis of clinical features and ATRX gene variants in a Chinese pedigree affected with X-linked alpha thalassemia mental retardation (ATR-X) syndrome / 中华医学遗传学杂志

OBJECTIVE@#To explore the clinical characteristics and genetic basis of two brothers featuring X-linked alpha thalassemia mental retardation (ATR-X) syndrome.@*METHODS@#An infant who had presented at the Qilu Children's Hospital in 2020 for unstable upright head and inability to roll over and his family were selected as the study subjects. The clinical features of the child and one of his brothers were summarized, and their genomic DNA was subjected to targeted capture and next generation sequencing (NGS).@*RESULTS@#The brothers had presented with mental retardation and facial dysmorphisms. NGS revealed that they had both harbored a hemizygous c.5275C>A variant of the ATRX gene located on the X chromosome, which was inherited from their mother.@*CONCLUSION@#The siblings were diagnosed with ATR-X syndrome. The discovery of the c.5275C>A variant has enriched the mutational spectrum of the ATRX gene.

Snyder-Robinson syndrome

Snyder-Robinson syndrome, also known as spermine synthase deficiency, is an X-linked intellectual disability syndrome (OMIM #390583). First described by Drs. Snyder and Robinson in 1969, this syndrome is characterized by an asthenic body habitus, facial dysmorphism, broad-based gait, and osteoporosis with frequent fractures. We report here a pediatric autopsy of a 4 year old male with a history of intellectual disability, gait abnormalities, multiple fractures, and seizures previously diagnosed with Snyder-Robinson syndrome with an SMS gene mutation (c.831G>T:p.L277F). The cause of death was hypoxic-ischemic encephalopathy secondary to prolonged seizure activity. Although Snyder-Robinson syndrome is rare, the need to recognize clinical findings in order to trigger genetic testing has likely resulted in under diagnosis.

Protocolo de estudio del retraso mental de origen genético / Study protocol of genetic mental retardation

El estudio del retraso mental de origen genético es uno de los campos más complejos en genética humana debido a que presenta una heterogeneidad muy elevada, con una gran complejidad de las bases genéticas y factores ambientales que influyen sobre éstas. En estos momentos, casi la mitad de los casos de retraso mental de origen genético quedan sin un diagnóstico. El objetivo de este trabajo es aportar una visión actualizada de las recientes metodologías desarrolladas para alcanzar un diagnóstico molecular de retraso mental de origen genético para poder dar asesoramiento genético y ofrecer un diagnóstico prenatal. El primer paso es la evaluación del paciente con una exploración clínica minuciosa y la obtención de datos sobre antecedentes personales y familiares. Cuando exista una sospecha diagnóstica de un síndrome clínico reconocible que cursa con retraso mental, ésta deberá ser confirmada en el laboratorio con la técnica correspondiente. Ante casos de retraso mental en los que no existe sospecha clínica para ningún síndrome determinado se realizarán tres pruebas de forma rutinaria: cariotipo, estudio molecular de la expansión CGG del gen FMR1 y estudio de las regiones subteloméricas. Hasta hace poco era difícil avanzar más, pero la reciente aparición de nuevas tecnologías de alto rendimiento cada vez más sensibles y con mayor capacidad de análisis como el MLPA o el aCGH (cariotipo molecular) está permitiendo la detección de nuevos reordenamientos crípticos desequilibrados responsables de retraso mental.

X linked mental retardation

Mental retardation [MR] is a group of heterogeneous clinical conditions. There are more than 900 genetic disorders associated with MR and it affects around 3%of the general population. Many MR conditions described are syndromic, fragile X syndrome being the most common clinical entity among them. Xlinked mental retardation [XLMR] is subdivided in two categories: syndromic XLMR [MRXS] when MR is associated with clinical features and non-syndromic XLMR [MRX] when MR is isolated. The aim of this systematic review of the literature was to join together the results of several studies related to X linked mental retardation and to present various genes implicated in this disease. In this review, focus has been given on genes implicated in mental retardation, the clinical data and on phenotype-genotype correlations. An exhaustive electronic and library research of the recent literature was carried out on the Web sites "Science Direct" and "Interscience Wiley". The key words used were "mental retardation", "X chromosome", "gene", "syndromic mental retardation", "non-syndromic mental retardation". In this review a number of X linked genes, the clinical features associated with the gene abnormality, and the prevalence of the disease gene are discussed. We classified these genes by order of their first implication in MR. A table presented on the XLMR Update Web site who list the 82 known XLMR genes is available as XLMR Genes and corresponding proteins

Allan-Herndon-Dudley syndrome.

Allan-Herndon-Dudley Syndrome (AHDS) is a rare X-linked disorder caused by mutation in the gene encoding the monocarboxylate transporter-8. Abnormal transport function is reflected by elevated free T3 and decreased free T4 levels along with clinical features characterized by neurological abnormalities including global developmental delay, central hypotonia, rotatory nystagmus, impaired hearing, spasticity and contractures of joints. We report a child with classical clinical features along with confirmatory deranged thyroid levels in blood.