Microcephaly is a medical condition involving a smaller-than-normal head. Microcephaly may be present at birth or it may develop in the first few years of life. Brain development is often affected; people with this disorder often have an intellectual disability, poor motor function, poor speech, abnormal facial features, seizures and dwarfism.
Macrocephaly is a condition in which circumference of the human head is abnormally large. It may be pathological or harmless, and can be a familial genetic characteristic. People diagnosed with macrocephaly will receive further medical tests to determine whether the syndrome is accompanied by particular disorders. Those with benign or familial macrocephaly are considered to have megalencephaly.
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.
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.
The Olduvai domain, known until 2018 as DUF1220 and the NBPF repeat, is a protein domain that shows a striking human lineage-specific (HLS) increase in copy number and appears to be involved in human brain evolution. The protein domain has also been linked to several neurogenetic disorders such as schizophrenia and increased severity of autism. In 2018, it was named by its discoverers after Olduvai Gorge in Tanzania, one of the most important archaeological sites for early humans, to reflect data indicating its role in human brain size and evolution.
Gap junction alpha-5 protein (GJA5), also known as connexin 40 (Cx40) — is a protein that in humans is encoded by the GJA5 gene.
B-cell CLL/lymphoma 9 protein is a protein that in humans is encoded by the BCL9 gene.
DECIPHER is a web-based resource and database of genomic variation data from analysis of patient DNA. It documents submicroscopic chromosome abnormalities and pathogenic sequence variants, from over 25000 patients and maps them to the human genome using Ensembl or UCSC Genome Browser. In addition it catalogues the clinical characteristics from each patient and maintains a database of microdeletion/duplication syndromes, together with links to relevant scientific reports and support groups.
8p23.1 duplication syndrome is a rare genetic disorder caused by a duplication of a region from human chromosome 8. This duplication syndrome has an estimated prevalence of 1 in 64,000 births and is the reciprocal of the 8p23.1 deletion syndrome. The 8p23.1 duplication is associated with a variable phenotype including one or more of speech delay, developmental delay, mild dysmorphism, with prominent forehead and arched eyebrows, and congenital heart disease (CHD).
3q29 microdeletion syndrome is a rare genetic disorder resulting from the deletion of a segment of chromosome 3. This syndrome was first described in 2005.
1q21.1 deletion syndrome is a rare aberration of chromosome 1. A human cell has one pair of identical chromosomes on chromosome 1. With the 1q21.1 deletion syndrome, one chromosome of the pair is not complete, because a part of the sequence of the chromosome is missing. One chromosome has the normal length and the other is too short.
22q11.2 duplication syndrome is a rare genetic disorder caused by a duplication of a segment at the end of chromosome 22.
Distal 18q- is a genetic condition caused by a deletion of genetic material within one of the two copies of chromosome 18. The deletion involves the distal section of 18q and typically extends to the tip of the long arm of chromosome 18.
1q21.1 copy number variations (CNVs) are rare aberrations of human chromosome 1.
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).
The neuroblastoma breaking point family (NBPF) is a family of genes involved in neuronal development. The family is highly specific to primates, with minimal similarity or presence in other mammals and no presence in other animals, and its genes' content has been subject to a very high number of duplications in humans. It was described by Vandepoele et al. in 2005 and named as such because NBPF1 was found to be broken by a chromosomal translocation in a neuroblastoma patient.
17q12 microdeletion syndrome, also known as 17q12 deletion syndrome, is a rare chromosomal anomaly caused by the deletion of a small amount of material from a region in the long arm of chromosome 17. It is typified by deletion of the HNF1B gene, resulting in kidney abnormalities and renal cysts and diabetes syndrome. It also has neurocognitive effects, and has been implicated as a genetic factor for autism and schizophrenia.
DiGeorge syndrome, also known as 22q11.2 deletion syndrome, is a syndrome caused by a microdeletion on the long arm of chromosome 22. While the symptoms can vary, they often include congenital heart problems, specific facial features, frequent infections, developmental disability, intellectual disability and cleft palate. Associated conditions include kidney problems, schizophrenia, hearing loss and autoimmune disorders such as rheumatoid arthritis or Graves' disease.
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.
16p11.2 duplication syndrome is a genetic condition caused by duplication of region on chromosome 16. The odds of developing autism spectrum disorder are elevated and comparable to the rate with 16p11.2 deletion. The rate of having ADHD is higher than in people with deletion.
