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Proboscis (anomaly)
In teratology, a proboscis is a blind-ended, tube-like structure, commonly located in the middle of the face. It is commonly seen in severe forms of holoprosencephaly that include cyclopia and is usually the result of abnormal development of the nose. Types Proboscis formation is classified in four general types: holoprosencephalic proboscis, lateral nasal proboscis, supernumerary probosci, and disruptive proboscis. Holoprosencephalic proboscis A holoprosencephalic proboscis is found in holoprosencephaly (a condition in which the forebrain of the embryo fails to develop into two hemispheres as it should). In cyclopia or ethmocephaly, proboscis is an abnormally formed nose. In cyclopia, a single eye in the middle of the face is associated with arrhinia (absence of the nose) and usually with proboscis formation above the eye. In ethmocephaly Ethmocephaly is a type of cephalic disorder caused by holoprosencephaly. Ethmocephaly is the rarest phenotypic variant of a group of def ... [...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. The related term developmental toxicity includes all manifestations of abnormal development that are caused by environmental insult. These may include growth retardation, delayed mental development or other congenital disorders without any structural malformations. Teratogens are substances that may cause birth defects via a toxic effect on an embryo or fetus. Known teratogens include: retinol, thalidomide, mercury, alcohol, lead, polychlorinated biphenyls (PCBs), and 2,3,7,8-tetrachlorodibenzodioxin. Etymology The term was borrowed in 1842 from the French , where it was formed in 1830 from the Greek (word stem ), meaning "sign sent by the gods, portent, marvel, monster", and ('' -ology''), used to designate a discourse, treaty, science, theory ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Holoprosencephaly
Holoprosencephaly (HPE) is a cephalic disorder in which the prosencephalon (the forebrain of the embryo) fails to develop into two hemispheres, typically occurring between the 18th and 28th day of gestation. Normally, the forebrain is formed and the face begins to develop in the fifth and sixth weeks of human pregnancy. The condition also occurs in other species. Holoprosencephaly is estimated to occur in approximately 1 in every 250 conceptions and most cases are not compatible with life and result in fetal death in utero due to deformities to the skull and brain. However, holoprosencephaly is still estimated to occur in approximately 1 in every 8,000 live births. When the embryo's forebrain does not divide to form bilateral cerebral hemispheres (the left and right halves of the brain), it causes defects in the development of the face and in brain structure and function. The severity of holoprosencephaly is highly variable. In less severe cases, babies are born with normal or ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cyclopia
Cyclopia (named after the Greek mythology character cyclopes) is the most extreme form of holoprosencephaly and is a congenital disorder (birth defect) characterized by the failure of the embryonic prosencephalon to properly divide the orbits of the eye into two cavities. Its incidence is 1 in 16,000 in born animals and 1 in 200 in miscarried fetuses. Signs and symptoms Typically, the nose is either missing or not functional. This deformity (called proboscis) forms above the center eye and is characteristic of a form of cyclopia called rhinencephaly or rhinocephaly. Most such embryos are either naturally aborted or are stillborn upon delivery. Although cyclopia is rare, several cyclopic human babies are preserved in medical museums (e.g. The Vrolik Museum, Amsterdam, Trivandrum Medical College). Some extreme cases of cyclopia have been documented in farm animals (horses, sheep, pigs, and sometimes chickens). In such cases, the nose and mouth fail to form, or the nose grows ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Arrhinia
Arrhinia (alternatively spelled "arhinia") is the congenital partial or complete absence of the nose at birth. It is an extremely rare condition, with few reported cases in the history of modern medicine. It is generally classified as a craniofacial abnormality. The cause of arrhinia is not known. One study of the literature found that all cases had presented a normal antenatal history. Conditions Arrhinia is associated with the following conditions and syndromes: * Arrhinia with choanal atresia and microphthalmia syndrome (Bosma arhinia microphthalmia syndrome) * Holoprosencephaly 1 * Holoprosencephaly 13, X-linked * Holoprosencephaly-radial heart renal anomalies syndrome History The term " arrhinia" is derived from the Greek roots "a-" (absence) and "rhinos" (nose); it is alternatively spelled "arhinia." The phenomenon of congenital arrhinia, which refers to the complete absence of the nose from birth, was initially documented in French literature during the 1800s. Ove ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ethmocephaly
Ethmocephaly is a type of cephalic disorder caused by holoprosencephaly. Ethmocephaly is the rarest phenotypic variant of a group of defects called the holoprosencephaly (HPE) malformation sequence; other variants include cebocephaly, cyclopia, and median cleft palate. It consists of a proboscis separating narrow-set eyes with an absent nose and microphthalmia (abnormal smallness of one or both eyes). Cebocephaly, another facial anomaly, is characterized by a small, flattened nose with a single nostril situated below incomplete or underdeveloped closely set eyes. The least severe in the spectrum of facial anomalies is the median cleft lip, also called premaxillary agenesis. Although the causes of most cases of holoprosencephaly remain unknown, some may be due to dominant or chromosome causes. Such chromosomal anomalies as trisomy 13 and trisomy 18 have been found in association with holoprosencephaly, or other neural tube defects. Genetic counseling and genetic testing, such a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cebocephaly
Cebocephaly (from Greek ''kebos'', "monkey" + ''kephale'', "head") is a developmental anomaly that is part of a group of defects called holoprosencephaly. Cebocephaly involves the presence of two separate eyes set close together and a small, flat nose with a single nostril (no nasal septum). It may be diagnosed before or after birth. It has a very poor prognosis, with most affected infants dying soon after birth. It is very rare, having been estimated to affect around 1 in 40,000 deliveries. Signs and symptoms Cebocephaly causes: * two separate eyes set close together * a small, flat nose with a single nostril * ear abnormalities * mouth abnormalities (such as microstomia) The presence of a nasal septum precludes a diagnosis of cebocephaly. Cebocephaly may cause malformations of the sphenoid and ethmoid bones behind the orbit. Cause Cebocephaly can be caused by many factors, particularly genetic variations. These include 18p-, 14q deletion, 13q deletion, and some verti ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
