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Concept: Mental retardation


BACKGROUND: Propionic acidemia is an inherited disorder caused by deficiency of propionyl-CoA carboxylase. Although it is one of the most frequent organic acidurias, information on the outcome of affected individuals is still limited.Study design/methods: Clinical and outcome data of 55 patients with propionic acidemia from 16 European metabolic centers were evaluated retrospectively. 35 patients were diagnosed by selective metabolic screening while 20 patients were identified by newborn screening. Endocrine parameters and bone age were assessed. In addition, IQ testing was performed and the patients' and their families' quality of life was assessed. RESULTS: The vast majority of patients (>85%) presented with metabolic decompensation in the neonatal period. Asymptomatic individuals were the exception. About three quarters of the study population was mentally retarded, median IQ was 55. Apart from neurologic symptoms, complications comprised hematologic abnormalities, cardiac diseases, feeding problems and impaired growth. Most patients considered their quality of life high. However, according to the parents' point of view psychic problems were four times more common in propionic acidemia patients than in healthy controls. CONCLUSION: Our data show that the outcome of propionic acidemia is still unfavourable, in spite of improved clinical management. Many patients develop long-term complications affecting different organ systems. Impairment of neurocognitive development is of special concern. Nevertheless, self-assessment of quality of life of the patients and their parents yielded rather positive results.

Concepts: Medicine, Infant, Pediatrics, Intelligence quotient, Mental retardation, Propionyl-CoA carboxylase, Propionic acidemia, Propionyl-CoA


INTRODUCTION: The Borderline Intellectual Functioning (BIF) is conceptualized as the frontier that delimits “normal” intellectual functioning from intellectual disability (IQ 71-85). In spite of its magnitude, its prevalence cannot be quantified and its diagnosis has not yet been defined. OBJECTIVES: To elaborate a conceptual framework and to establish consensus guidelines. METHOD: A mixed qualitative methodology, including frame analysis and nominal groups techniques, was used. The literature was extensively reviewed in evidence based medical databases, scientific publications, and the grey literature. This information was studied and a framing document was prepared. RESULTS: Scientific publications covering BIF are scarce. The term that yields a bigger number of results is “Borderline Intelligence”. The Working Group detected a number of areas in which consensus was needed and wrote a consensus document covering the conclusions of the experts and the framing document. CONCLUSIONS: It is a priority to reach an international consensus about the BIF construct and its operative criteria, as well as to develop specific tools for screening and diagnosis. It is also necessary to define criteria that enable its incidence and prevalence. To know what interventions are the most efficient, and what are the needs of this population, is vital to implement an integral model of care centred on the individual.

Concepts: Evidence-based medicine, Literature, Intelligence quotient, Intelligence, Mental retardation, Disability, Concept, Borderline intellectual functioning


Distinct isoforms of the PI3K catalytic subunit have specialized functions in the brain, but their role in cognition is unknown. Here, we show that the catalytic subunit p110β plays an important role in prefrontal cortex (PFC)-dependent cognitive defects in mouse models of Fragile X syndrome (FXS), an inherited intellectual disability. FXS is caused by loss of function of the fragile X mental retardation protein (FMRP), which binds and translationally represses mRNAs. PFC-selective knockdown of p110β, an FMRP target that is translationally upregulated in FXS, reverses deficits in higher cognition in Fmr1 knockout mice. Genetic full-body reduction of p110β in Fmr1 knockout mice normalizes excessive PI3K activity, restores stimulus-induced protein synthesis, and corrects increased dendritic spine density and behavior. Notably, adult-onset PFC-selective Fmr1 knockdown mice show impaired cognition, which is rescued by simultaneous p110β knockdown. Our results suggest that FMRP-mediated control of p110β is crucial for neuronal protein synthesis and cognition.

Concepts: Brain, Autism, Down syndrome, Mental retardation, Disability, Fragile X syndrome, FMR1, Dendritic spine


Despite increased awareness and concern about children with developmental disabilities wandering away from adult supervision, there is a paucity of research about elopement. This is the first study to examine and report the prevalence and correlates of elopement in a nationally representative sample of school-age children in the United States with an autism spectrum disorder (ASD) and/or cognitive impairment. Data were obtained from the CDC’s “Pathways” Survey, a follow-up telephone survey of the parents of 4,032 children with a developmental condition. 3,518 children that had ASD, intellectual disability (ID), and/or developmental delay (DD) at the time of survey administration were included for analysis. Children were divided into three condition groups: ASD-only; ID/DD-only; ASD+ID/DD. Logistic regression analyses were used to compare the prevalence of elopement and rates of preventive measure use (barriers and/or electronic devices) across condition groups, and to examine the clinical and demographic correlates of elopement. T-tests were also performed to compare scores on the Children’s Social Behavior Questionnaire (CSBQ) between wanderers and non-wanderers. Overall, 26.7% of children had reportedly eloped within the previous year, most commonly from public places. Children with ASD-only and ASD+ID/DD were more likely to have eloped than those with ID/DD-only. Across all groups, wanderers scored higher than non-wanderers on five out of six CSBQ subscales; they were more likely not to realize when there is danger, to have difficulty distinguishing between strangers and familiar people, to show sudden mood changes, to over-react to everything/everyone, to get angry quickly, to get lost easily, and to panic in new situations or if change occurs. Even after controlling for elopement history, parents of children in the ASD+ID/DD group were more likely than those in the other condition groups to report using physical or electronic measures to prevent wandering.

Concepts: Regression analysis, United States, Autism, Down syndrome, Autism spectrum, Mental retardation, Developmental disability, Disability


Alcohol is a teratogen.* Prenatal alcohol exposure is associated with a range of adverse reproductive outcomes and can cause fetal alcohol spectrum disorders (FASDs) characterized by lifelong physical, behavioral, and intellectual disabilities. FASDs are completely preventable if a woman does not drink alcohol while pregnant.

Concepts: Pregnancy, Prenatal development, Fetus, Mental retardation, Fetal alcohol syndrome


Fragile X-associated disorders are a family of genetic conditions resulting from the partial or complete loss of fragile X mental retardation protein (FMRP). Among these disorders is fragile X syndrome (FXS), the most common cause of inherited intellectual disability and autism. Progress in basic neuroscience has led to identification of molecular targets for treatment in FXS; however, there is a gap in translation to targeted therapies in humans. The present study introduces a novel therapeutic target for FXS: nuclear factor (erythroid-derived 2)-like 2 (Nrf2), a transcription factor known to induce expression of over 100 cytoprotective genes. We also demonstrate that NNZ2566, a drug that has successfully completed a phase 2 clinical trial in FXS, is effective in modulating this target in FXS, partially reversing the FXS phenotype: NNZ2566 has a therapeutic role as Nrf2 activator. Effectively, treatment with NNZ2566 normalizes the translocation of Nrf2 to the nucleus, inducing expression of numerous oxidative stress related genes including NQO1, GST-α1 and EH and has a knockdown effect on E-cadherin. In summary, the Nrf2/ARE pathway appears to be a novel promising therapeutic target for FXS and NNZ2566 appears to be acting as an activator of the Nrf2/ARE pathway and suggests a potential benefit across multiple symptoms that could be associated with the pathobiological processes underlying FXS.

Concepts: DNA, Gene, Genetics, Gene expression, Transcription, Autism, Mental retardation, Fragile X syndrome


Although microcephaly is a feature of Fetal Alcohol Syndrome, it is currently unknown whether low-to-moderate prenatal alcohol exposure affects head circumference. Small magnitude associations reported in observational studies are likely to be misleading due to confounding and misclassification biases. Alternative analytical approaches such as the use of family negative controls (e.g. comparing the effects of maternal and paternal exposure) could help disentangle causal effects. We investigated the association of maternal and paternal alcohol drinking before and early in pregnancy with infant head circumference, using data from 68,244 mother-father-offspring trios from the Norwegian Mother and Child Cohort Study (MoBa) (1999-2009). In analyses adjusted for potential confounders, we found no consistent pattern of association between maternal or paternal alcohol intake before or during pregnancy and offspring head circumference modelled as a continuous outcome. However, we found higher odds of microcephaly at birth for higher paternal, but not maternal, alcohol consumption before pregnancy, and similar but weaker effect estimates for first trimester drinking. Associations with paternal drinking before pregnancy were unexpected and should be regarded as hypothesis generating, until independently replicated, although potentially important given the absence of guidelines on safe drinking levels for men in couples trying for a pregnancy.

Concepts: Alcohol, Pregnancy, Prenatal development, Mental retardation, Mother, Fetal alcohol syndrome, Microcephaly, Recommended maximum intake of alcoholic beverages


Fragile X syndrome (FXS), the most common monogenic cause of inherited intellectual disability and autism, is caused by the silencing of the FMR1 gene, leading to the loss of fragile X mental retardation protein (FMRP), a synaptically expressed RNA-binding protein regulating translation. The Fmr1 knockout model recapitulates the main traits of the disease. Uncontrolled activity of metabotropic glutamate receptor 5 (mGluR5) and mammalian target of rapamycin (mTOR) signaling seem crucial in the pathology of this disease. The endocannabinoid system (ECS) is a key modulator of synaptic plasticity, cognitive performance, anxiety, nociception and seizure susceptibility, all of which are affected in FXS. The cannabinoid receptors CB1 (CB1R) and CB2 (CB2R) are activated by phospholipid-derived endocannabinoids, and CB1R-driven long-term regulation of synaptic strength, as a consequence of mGluR5 activation, is altered in several brain areas of Fmr1 knockout mice. We found that CB1R blockade in male Fmr1 knockout (Fmr1(-/y)) mice through pharmacological and genetic approaches normalized cognitive impairment, nociceptive desensitization, susceptibility to audiogenic seizures, overactivated mTOR signaling and altered spine morphology, whereas pharmacological blockade of CB2R normalized anxiolytic-like behavior. Some of these traits were also reversed by pharmacological inhibition of mTOR or mGluR5. Thus, blockade of ECS is a potential therapeutic approach to normalize specific alterations in FXS.

Concepts: Protein, Receptor, Autism, Metabotropic glutamate receptor, Cannabinoid receptor, Mental retardation, Fragile X syndrome, FMR1


BACKGROUND: Despite resolution of the symptoms of eating and/or swallowing disorders, prolonged tube feeding is maintained in some children. This study summarized the characteristics of children with tube dependence and investigated the causes of tube dependence. METHODS: Clinical and growth data were evaluated using medical records and referral forms for 35 tube-dependent children. RESULTS: The children in this study had a median age of 30 months (range, 17-37 months) on the first visit and 35.5 months (range, 21.3-44.8 months) at tube removal. Seven children were not weaned from the feeding tube within the study period. Twenty-two (63%) of the children were girls, 20 (57%) were able to walk, 24 (69%) had mild mental retardation, and 33 (94%) had underlying disease. Tube-dependent children tended to weigh less than age-matched normal children. Sixteen (45.7%) children were underweight. Children who had their feeding tubes removed before age 3 were significantly younger at the initial visit than those who had their tubes removed after 3 years of age. Increased finger feeding was observed during the period before tube removal. CONCLUSION: tube-dependent children tend to be close to normal in body growth and intellectual development. When weaning from tube feeding, interventions at earlier ages are more efficient. Reduction in or discontinuation of tube feeding and encouraging feeding self were effective to wean off tube feeding.

Concepts: Feeding tube, Mental retardation, Weaning


Immune abnormalities have been described in some individuals with autism spectrum disorders (ASDs) as well as their family members. However, few studies have directly investigated the role of prenatal cytokine and chemokine profiles on neurodevelopmental outcomes in humans. In the current study, we characterized mid-gestational serum profiles of 22 cytokines and chemokines in mothers of children with ASD (N=415), developmental delay (DD) without ASD (N=188), and general population (GP) controls (N=428) using a bead-based multiplex technology. The ASD group was further divided into those with intellectual disabilities (developmental/cognitive and adaptive composite score<70) (ASD+ID, N=184) and those without (composite score⩾70) (ASD-noID, N=201). Levels of cytokines and chemokines were compared between groups using multivariate logistic regression analyses, adjusting for maternal age, ethnicity, birth country and weight, as well as infant gender, birth year and birth month. Mothers of children with ASD+ID had significantly elevated mid-gestational levels of numerous cytokines and chemokines, such as granulocyte macrophage colony-stimulating factor, interferon-γ, interleukin-1α (IL-1α) and IL-6, compared with mothers of children with either ASD-noID, those with DD, or GP controls. Conversely, mothers of children with either ASD-noID or with DD had significantly lower levels of the chemokines IL-8 and monocyte chemotactic protein-1 compared with mothers of GP controls. This observed immunologic distinction between mothers of children with ASD+ID from mothers of children with ASD-noID or DD suggests that the intellectual disability associated with ASD might be etiologically distinct from DD without ASD. These findings contribute to the ongoing efforts toward identification of early biological markers specific to subphenotypes of ASD.Molecular Psychiatry advance online publication, 24 May 2016; doi:10.1038/mp.2016.77.

Concepts: Immune system, Regression analysis, Cytokines, Autism, Chemokine, Down syndrome, Mental retardation, Developmental disability