Fragile X syndrome (FXS) is a genetic neurodevelopmental disorder characterized by mild-to-moderate intellectual disability. The average IQ in males with FXS is under 55, while about two thirds of affected females are intellectually disabled. Physical features may include a long and narrow face, large ears, flexible fingers, and large testicles. About a third of those affected have features of autism such as problems with social interactions and delayed speech. Hyperactivity is common, and seizures occur in about 10%. Males are usually more affected than females.
Megalencephaly is a growth development disorder in which the brain is abnormally large. It is characterized by a brain with an average weight that is 2.5 standard deviations above the mean of the general population. Approximately 1 out of 50 children (2%) are said to have the characteristics of megalencephaly in the general population.
The heritability of autism is the proportion of differences in expression of autism that can be explained by genetic variation; if the heritability of a condition is high, then the condition is considered to be primarily genetic. Autism has a strong genetic basis. Although the genetics of autism are complex, autism spectrum disorder (ASD) is explained more by multigene effects than by rare mutations with large effects.
Histone H4 is one of the five main histone proteins involved in the structure of chromatin in eukaryotic cells. Featuring a main globular domain and a long N-terminal tail, H4 is involved with the structure of the nucleosome of the 'beads on a string' organization. Histone proteins are highly post-translationally modified. Covalently bonded modifications include acetylation and methylation of the N-terminal tails. These modifications may alter expression of genes located on DNA associated with its parent histone octamer. Histone H4 is an important protein in the structure and function of chromatin, where its sequence variants and variable modification states are thought to play a role in the dynamic and long term regulation of genes.
22q13 deletion syndrome, known as Phelan–McDermid syndrome (PMS), is a genetic disorder caused by deletions or rearrangements on the q terminal end of chromosome 22. Any abnormal genetic variation in the q13 region that presents with significant manifestations (phenotype) typical of a terminal deletion may be diagnosed as 22q13 deletion syndrome. There is disagreement among researchers as to the exact definition of 22q13 deletion syndrome. The Developmental Synaptopathies Consortium defines PMS as being caused by SHANK3 mutations, a definition that appears to exclude terminal deletions. The requirement to include SHANK3 in the definition is supported by many but not by those who first described 22q13 deletion syndrome.
Pitt–Hopkins syndrome (PTHS) is a rare genetic disorder characterized by developmental delay, moderate to severe intellectual disability, distinctive facial features, and possible intermittent hyperventilation followed by apnea. Epilepsy often occurs in Pitt-Hopkins. It is part of the clinical spectrum of Rett-like syndromes. Pitt-hopkins syndrome is clinically similar to Angelman syndrome, Rett-syndrome, Mowat Wilson syndrome, and ATR-X syndrome.
Autism, also called autism spectrum disorder (ASD), is a neurodevelopmental disorder characterized by symptoms of deficient reciprocal social communication and the presence of restricted, repetitive, and inflexible patterns of behavior. Autism generally affects a person's ability to understand and connect with others, as well as their adaptability to everyday situations, with its severity and support needs varying widely across the spectrum. For example, some are nonspeaking, while others have very proficient spoken language.
SET binding protein 1 is a protein that in humans is encoded by the SETBP1 gene.
Sotos syndrome is a rare genetic disorder characterized by excessive physical growth during the first years of life. Excessive growth often starts in infancy and continues into the early teen years. The disorder may be accompanied by autism, mild intellectual disability, delayed motor, cognitive, and social development, hypotonia, and speech impairments. Children with Sotos syndrome tend to be large at birth and are often taller, heavier, and have relatively large skulls (macrocephaly) than is normal for their age. Signs of the disorder, which vary among individuals, include a disproportionately large skull with a slightly protrusive forehead, large hands and feet, large mandible, hypertelorism, and downslanting eyes. Clumsiness, an awkward gait, and unusual aggressiveness or irritability may also occur.
Dup15q syndrome is the common name for maternally inherited chromosome 15q11.2-q13.1 duplication syndrome. This is a genomic copy number variant that leads to a type of neurodevelopmental disorder, caused by partial duplication of the proximal long arm of Chromosome 15. This variant confers a strong risk for autism spectrum disorder, epilepsy, and intellectual disability. It is the most common genetic cause of autism, accounting for approximately 1-3% of cases. Dup15q syndrome includes both interstitial duplications and isodicentric duplications of 15q11.2-13.1.
Activity-dependent neuroprotector homeobox is a protein that in humans is encoded by the ADNP gene.
Nagwa Abdel Meguid is an Egyptian geneticist and 2002 winner of the L’Oreal UNESCO Award for Women in Science for Africa and the Middle East. Her research has "identified several genetic mutations that cause common syndromes such as the fragile X syndrome and Autism".
Burnside–Butler syndrome is a name that has been applied to the effects of microdeletion of DNA sequences involving four neurodevelopmental genes. Varying developmental and psychiatric disorders have been attributed to the microdeletion; however, the great majority of people with the deletion do not have any clinical features associated with it. More studies are needed to delineate the range of clinical presentation.
Xp11.2 duplication is a genomic variation marked by the duplication of an X chromosome region on the short arm p at position 11.2, defined by standard karyotyping (G-banding). This gene-rich, rearrangement prone region can be further divided into three loci - Xp11.21, Xp11.22 and Xp11.23. The duplication could involve any combination of these three loci. While the length of the duplication can vary from 0.5Mb to 55 Mb, most duplications measure about 4.5Mb and typically occur in the region of 11.22-11.23. Most affected females show preferential activation of the duplicated X chromosome. Features of affected individuals vary significantly, even among members of the same family. The Xp11.2 duplication can be 'silent' - presenting no obvious symptoms in carriers - which is known from the asymptomatic parents of affected children carrying the duplication. The common symptoms include intellectual disabilities, speech delay and learning difficulties, while in rare cases, children have seizures and a recognizable brain wave pattern when assessed by EEG (electroencephalography).
Methyl-CpG binding domain protein 5 is a protein that in humans is encoded by the MBD5 gene.
White–Sutton syndrome (WHSUS) is a rare neurodevelopmental disorder that affects different systems of the human body. It is mainly characterized by developmental delay, intellectual disability, craniofacial abnormalities and commonly features of autism spectrum disorder (ASD).
CHAMP1-associated intellectual disability syndrome, also known as autosomal dominant intellectual disability type 40, is a rare genetic disorder characterized by intellectual disabilities, developmental delays, facial dysmorphisms, and other anomalies.
Autosomal dominant intellectual disability-craniofacial anomalies-cardiac defects syndrome is a rare genetic disorder which is characterized by multi-systemic symptoms primarily affecting the intellect and post-natal development.
Severe intellectual disability-progressive spastic diplegia syndrome is a rare novel genetic disorder characterized by severe intellectual disabilities, ataxia, craniofacial dysmorphisms, and muscle spasticity. It is a type of autosomal dominant syndromic intellectual disability.
16p11.2 deletion syndrome is a rare genetic condition caused by microdeletion on the short arm of chromosome 16. Most affected individuals experience global developmental delay and intellectual disability, as well as childhood-onset obesity. 16p11.2 deletion is estimated to account for approximately 1% of autism spectrum disorder cases.
