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Tetrasomy X
Tetrasomy X, also known as 48,XXXX, is a chromosomal disorder in which a female has four, rather than two, copies of the X chromosome. It is associated with intellectual disability of varying severity, characteristic "coarse" facial features, heart defects, and skeletal anomalies such as increased height, clinodactyly (incurved pinky fingers), and radioulnar synostosis (fusion of the long bones in the forearm). Tetrasomy X is a rare condition, with few medically recognized cases; it is estimated to occur in approximately 1 in 50,000 females. The disorder has a wide range of symptoms, with phenotypes (presentations) ranging from slight to severe. It is suspected to be underdiagnosed, as are other sex chromosome disorders. Life outcomes vary; some women have had education, employment, and children, while others have remained dependent into adulthood. Life expectancy does not appear to be substantially reduced. Tetrasomy X has phenotypic overlap with a number of more common di ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Trisomy X
Trisomy X, also known as triple X syndrome and characterized by the karyotype 47,XXX, is a chromosome disorder in which a female has an extra copy of the X chromosome. It is relatively common and occurs in 1 in 1,000 females, but is rarely diagnosed; fewer than 10% of those with the condition know they have it. Those who have symptoms can have learning disabilities, mild dysmorphic features such as hypertelorism (wide-spaced eyes) and clinodactyly (incurved little fingers), early menopause, and increased height. As the symptoms of trisomy X are often not serious enough to prompt a karyotype test, many cases of trisomy X are diagnosed before birth via prenatal screening tests such as amniocentesis. Most females with trisomy X live normal lives, although their socioeconomic status is reduced compared to the general population. Trisomy X occurs via a process called nondisjunction, in which normal cell division is interrupted and produces gametes with too many or too few chromosomes ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Teratology
Teratology is the study of abnormalities of physiological development in organisms during their life span. It is a sub-discipline in medical genetics which focuses on the classification of congenital abnormalities in dysmorphology caused by teratogens and also in pharmacology and toxicology. Teratogens are substances that may cause non-heritable birth defects via a toxic effect on an embryo or fetus. Defects include malformations, disruptions, deformations, and dysplasia that may cause stunted growth, delayed mental development, or other congenital disorders that lack structural malformations. These defects can be recognized prior to or at birth as well as later during early childhood. The related term developmental toxicity includes all manifestations of abnormal development that are caused by environmental insult. The extent to which teratogens will impact an embryo is dependent on several factors, such as how long the embryo has been exposed, the stage of development the ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Karyotype
A karyotype is the general appearance of the complete set of chromosomes in the cells of a species or in an individual organism, mainly including their sizes, numbers, and shapes. Karyotyping is the process by which a karyotype is discerned by determining the chromosome complement of an individual, including the number of chromosomes and any abnormalities. A karyogram or idiogram is a graphical depiction of a karyotype, wherein chromosomes are generally organized in pairs, ordered by size and position of centromere for chromosomes of the same size. Karyotyping generally combines light microscopy and photography in the metaphase of the cell cycle, and results in a photomicrographic (or simply micrographic) karyogram. In contrast, a schematic karyogram is a designed graphic representation of a karyotype. In schematic karyograms, just one of the sister chromatids of each chromosome is generally shown for brevity, and in reality they are generally so close together that they look as ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Dysmorphic Feature
A dysmorphic feature is an abnormal difference in body structure. It can be an isolated finding in an otherwise normal individual, or it can be related to a congenital disorder, genetic syndrome or birth defect. Dysmorphology is the study of dysmorphic features, their origins and proper nomenclature. One of the key challenges in identifying and describing dysmorphic features is the use and understanding of specific terms between different individuals. Clinical geneticists and pediatricians are usually those most closely involved with the identification and description of dysmorphic features, as most are apparent during childhood. Dysmorphic features can vary from isolated, mild anomalies such as clinodactyly or synophrys to severe congenital anomalies, such as heart defects and holoprosencephaly. In some cases, dysmorphic features are part of a larger clinical picture, sometimes known as a sequence, syndrome or association. Recognizing the patterns of dysmorphic features is an i ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Hypertelorism
Hypertelorism is an abnormally increased distance between two organs or bodily parts, usually referring to an increased distance between the orbits (eyes), or orbital hypertelorism. In this condition, the distance between the inner eye corners, as well as the distance between the pupils, is greater than normal. Hypertelorism should not be confused with telecanthus, in which the distance between the inner eye corners is increased, but the distances between the outer eye corners and the pupils remain unchanged.Michael L. Bentz: ''Pediatric Plastic Surgery''; Chapter 9 Hypertelorism by Renato Ocampo, Jr., MD/ John A. Persing, MD Hypertelorism is a symptom in a variety of syndromes, including Edwards syndrome (trisomy 18), 1q21.1 duplication syndrome, basal cell nevus syndrome, DiGeorge syndrome and Loeys–Dietz syndrome. Hypertelorism can also be seen in Apert syndrome, Autism spectrum disorder, craniofrontonasal dysplasia, Noonan syndrome, neurofibromatosis, LEOPARD syndrome ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Epicanthic Folds
An epicanthic fold or epicanthus is a skin fold of the upper eyelid that covers the inner corner (medial canthus) of the eye. However, variation occurs in the nature of this feature and the presence of "partial epicanthic folds" or "slight epicanthic folds" is noted in the relevant literature. Various factors influence whether epicanthic folds form, including ancestry, age, and certain medical conditions. The primary cause of the epicanthic fold is the hypertrophy of the preseptal portion of the orbicularis oculi muscle. Etymology ''Epicanthus'' means 'above the canthus', with epi-canthus being the Latinized form of the Ancient Greek : 'corner of the eye'. Classification Variation in the shape of the epicanthic fold has led to four types being recognised: * ''Epicanthus supraciliaris'' runs from the brow, curving downwards towards the lachrymal sac. * ''Epicanthus palpebralis'' begins above the upper tarsus and extends to the inferior orbital rim. * ''Epicanthus tarsa ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Polysomy
Polysomy is a condition found in many species, including fungi, plants, insects, and mammals, in which an organism has at least one more chromosome than normal, i.e., there may be three or more copies of the chromosome rather than the expected two copies. Most eukaryotic species are diploid, meaning they have two sets of chromosomes, whereas prokaryotes are haploid, containing a single chromosome in each cell. Aneuploids possess chromosome numbers that are not exact multiples of the haploid number and polysomy is a type of aneuploidy. A karyotype is the set of chromosomes in an organism and the suffix -''somy'' is used to name aneuploid karyotypes. This is not to be confused with the suffix -''ploidy'', referring to the number of complete sets of chromosomes. Polysomy is usually caused by non-disjunction (the failure of a pair of homologous chromosomes to separate) during meiosis, but may also be due to a translocation mutation (a chromosome abnormality caused by rearrangement ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Sex Chromosome
Sex chromosomes (also referred to as allosomes, heterotypical chromosome, gonosomes, heterochromosomes, or idiochromosomes) are chromosomes that carry the genes that determine the sex of an individual. The human sex chromosomes are a typical pair of mammal allosomes. They differ from autosomes in form, size, and behavior. Whereas autosomes occur in homologous pairs whose members have the same form in a diploid cell, members of an allosome pair may differ from one another. Nettie Stevens and Edmund Beecher Wilson both independently discovered sex chromosomes in 1905. However, Stevens is credited for discovering them earlier than Wilson. Differentiation In humans, each cell nucleus contains 23 pairs of chromosomes, a total of 46 chromosomes. The first 22 pairs are called autosomes. Autosomes are homologous chromosomes i.e. chromosomes which contain the same genes (regions of DNA) in the same order along their chromosomal arms. The 23rd pair of chromosomes are called allosomes. Th ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Aneuploidy
Aneuploidy is the presence of an abnormal number of chromosomes in a cell (biology), cell, for example a human somatic (biology), somatic cell having 45 or 47 chromosomes instead of the usual 46. It does not include a difference of one or more ploidy#Haploid and monoploid, complete sets of chromosomes. A cell with any number of complete chromosome sets is called a ''ploidy#Euploid, euploid'' cell. An extra or missing chromosome is a common cause of some genetic disorders. Some cancer cells also have abnormal numbers of chromosomes. About 68% of human solid tumors are aneuploid. Aneuploidy originates during cell division when the chromosomes do not separate properly between the two cells (nondisjunction). Most cases of aneuploidy in the autosomes result in miscarriage, and the most common extra autosomal chromosomes among live births are Down syndrome, 21, Edwards syndrome, 18 and Patau syndrome, 13. Chromosome abnormality, Chromosome abnormalities are detected in 1 of 160 live huma ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Language Delay
Language is a structured system of communication that consists of grammar and vocabulary. It is the primary means by which humans convey meaning, both in spoken and signed forms, and may also be conveyed through writing. Human language is characterized by its cultural and historical diversity, with significant variations observed between cultures and across time. Human languages possess the properties of productivity and displacement, which enable the creation of an infinite number of sentences, and the ability to refer to objects, events, and ideas that are not immediately present in the discourse. The use of human language relies on social convention and is acquired through learning. Estimates of the number of human languages in the world vary between and . Precise estimates depend on an arbitrary distinction (dichotomy) established between languages and dialects. Natural languages are spoken, signed, or both; however, any language can be encoded into secondary med ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Speech Delay
Speech delay, also known as alalia, refers to a delay in the development or use of the mechanisms that produce speech. Speech – as distinct from language – is the actual process of making sounds, using such organs and structures as the lungs, vocal cords, mouth, tongue, teeth, etc. Language delay refers to a delay in the development or use of the knowledge of language. Because language and speech are two independent stages, they may be individually delayed. For example, a child may be delayed in speech (i.e., unable to produce intelligible speech sounds), but not delayed in language. In this case, the child would be attempting to produce an age appropriate amount of language, but that language would be difficult or impossible to understand. Conversely, since a child with a language delay typically has not yet had the opportunity to produce speech sounds, they are likely to have a delay in speech as well. Signs and symptoms The warning signs of early speech delay are ca ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
