| 词条 | Holoprosencephaly |
| 释义 |
| name = Holoprosencephaly | field = Medical genetics | image = EmbryonicBrain.svg | caption = Diagram depicting the main subdivisions of the embryonic vertebrate brain. | symptoms = | complications = | onset = | duration = | types = | causes = | risks = | diagnosis = | differential = | prevention = | treatment = | medication = | prognosis = | frequency = | deaths = }} Holoprosencephaly (HPE) is a cephalic disorder in which the prosencephalon (the forebrain of the embryo) fails to develop into two hemispheres. 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. The condition can be mild or severe. Most cases are not compatible with life and result in fetal death in utero.[1] 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. In less severe cases, babies are born with normal or near-normal brain development and facial deformities that may affect the eyes, nose, and upper lip. Signs and symptomsSymptoms of holoprosencephaly range from mild (no facial/organ defects, anosmia, or only a single central incisor) to moderate to severe (cyclopia). There are four classifications of holoprosencephaly.
Holoprosencephaly consists of a spectrum of defects or malformations of the brain and face. At the most severe end of this spectrum are cases involving serious malformations of the brain, malformations so severe that they often cause miscarriage or stillbirth. At the other end of the spectrum are individuals with facial defects which may affect the eyes, nose, and upper lip - and normal or near-normal brain development. Seizures and mental retardation may occur. The most severe of the facial defects (or anomalies) is cyclopia, an abnormality characterized by the development of a single eye, located in the area normally occupied by the root of the nose, and a missing nose or a nose in the form of a proboscis (a tubular appendage) located above the eye. The condition is also referred to as cyclocephaly or synophthalmia, and is very rare. CausesThe exact cause(s) of HPE are yet to be determined. Mutations in the gene encoding the Sonic Hedgehog protein, which is involved in the development of the central nervous system (CNS), can cause holoprosencephaly.[3][4][5] In other cases, it often seems that there is no specific cause at all.[6] GeneticsArmand Marie Leroi describes the cause of cyclopia as a genetic malfunctioning during the process by which the embryonic brain is divided into two.[7] Only later does the visual cortex take recognizable form, and at this point an individual with a single forebrain region will be likely to have a single, possibly rather large, eye (at such a time, individuals with separate cerebral hemispheres would form two eyes). Increases in expression of such genes as Pax-2, as well as inhibition of Pax-6, from the notochord have been implicated in normal differentiation of cephalic midline structures. Inappropriate expression of any of these genes may result in mild to severe forms of holoprosencephaly.{{Citation needed|date=September 2009}} Other candidate genes have been located, including the SHH (holoprosencephaly type 3 a.k.a. HPE3), TGIF, ZIC2, SIX3[8] and BOC genes.[9] Although many children with holoprosencephaly have normal chromosomes, specific chromosomal abnormalities have been identified in some patients (trisomy of chromosome 13, also known as Patau syndrome). There is evidence that in some families, HPE is inherited (autosomal dominant as well as autosomal or X-linked recessive inheritance).{{Citation needed|date=April 2011}} Features consistent with familial transmission of the disease (e.g., a single central maxillary incisor) should be carefully assessed in parents and family members. Non-genetic factorsNumerous possible risk factors have been identified, including gestational diabetes, transplacental infections (the "TORCH complex"), first trimester bleeding, and a history of miscarriage.[6][10] As well, the disorder is found twice as often in female babies.[10] However, there appears to be no correlation between HPE and maternal age.[10] There is evidence of a correlation between HPE and the use of various drugs classified as being potentially unsafe for pregnant and lactating mothers. These include insulin, birth control pills, aspirin, lithium, thorazine, retinoic acid, and anticonvulsants.[10] There is also a correlation between alcohol consumption and HPE, along with nicotine, the toxins in cigarettes and toxins in cigarette smoke when used during pregnancy.[10] PrognosisHPE is not a condition in which the brain deteriorates over time. Although serious seizure disorders, autonomic dysfunction, complicated endocrine disorders and other life-threatening conditions may sometimes be associated with HPE, the mere presence of HPE does not mean that these serious problems will occur or develop over time without any previous indication or warning. These abnormalities are usually recognized shortly after birth or early in life and only occur if areas of the brain controlling those functions are fused, malformed or absent. Prognosis is dependent upon the degree of fusion and malformation of the brain, as well as other health complications that may be present. The more severe forms of encephalopathy are usually fatal. This disorder consists of a spectrum of defects, malformations and associated abnormalities. Disability is based upon the degree in which the brain is affected. Moderate to severe defects may cause mental retardation, spastic quadriparesis, athetoid movements, endocrine disorders, epilepsy and other serious conditions; mild brain defects may only cause learning or behavior problems with few motor impairments. Seizures may develop over time with the highest risk before 2 years of age and the onset of puberty. Most are managed with one medication or a combination of medications. Typically, seizures that are difficult to control appear soon after birth, requiring more aggressive medication combinations/doses. Most children with HPE are at risk of having elevated blood sodium levels during moderate-severe illnesses, that alter fluid intake/output, even if they have no previous diagnosis of diabetes insipidus or hypernatremia. See also
References1. ^[https://www.ninds.nih.gov/Disorders/All-Disorders/Holoprosencephaly-Information-Page NINDS Holoencephalopathy Information Page] 2. ^{{cite book | pages=92–95 | chapter = Brain Malformations | title = Pediatric Neuroradiology: Brain, Head, Neck and Spine |editor1=Totori-Donati, Paolo |editor2=Rossi, Andrea |editor3=Raybaud, C. | year = 2005 | volume = 1 | isbn = 978-3-540-41077-5 | publisher = Springer |author1=Totori-Donati, Paolo |author2=Rossi, Andrea |author3=Biancheri, Roberta }} 3. ^{{cite journal|last1=Chiang|first1=C|last2=Litingtung|first2=Y|last3=Lee|first3=E|last4=Young|first4=KE|last5=Corden|first5=JL|last6=Westphal|first6=H|last7=Beachy|first7=PA|title=Cyclopia and defective axial patterning in mice lacking Sonic hedgehog gene function.|journal=Nature|date=3 October 1996|volume=383|issue=6599|pages=407–13|pmid=8837770|doi=10.1038/383407a0}} 4. ^{{cite journal|last1=Muenke|first1=M|last2=Beachy|first2=PA|title=Genetics of ventral forebrain development and holoprosencephaly.|journal=Current Opinion in Genetics & Development|date=June 2000|volume=10|issue=3|pages=262–9|pmid=10826992|doi=10.1016/s0959-437x(00)00084-8|url=https://zenodo.org/record/1260165}} 5. ^{{cite journal|last1=Rash|first1=BG|last2=Grove|first2=EA|title=Patterning the dorsal telencephalon: a role for sonic hedgehog?|journal=The Journal of Neuroscience|date=24 October 2007|volume=27|issue=43|pages=11595–603|pmid=17959802|doi=10.1523/jneurosci.3204-07.2007}} 6. ^1 {{cite web | url=http://www.stanford.edu/group/hpe/about/ | title=About Holoprosencephaly | author=The Carter Centers for Brain Research in Holoprosencephaly and Related Malformations | deadurl=yes | archiveurl=https://web.archive.org/web/20090514043807/http://www.stanford.edu/group/hpe/about/ | archivedate=2009-05-14 | df= }} 7. ^Armand Marie Leroi, Mutants: On the Form, Varieties and Errors of the Human Body, 2003, Harper Perennial, London. {{ISBN|0-00-653164-4}} 8. ^The Carter Center for Research in holoprosencephaly and {{webarchive|url=https://web.archive.org/web/20081121181528/http://www.holoprosencephaly.net/ |date=2008-11-21 }} 9. ^Hong M, Srivastava K, Kim S, Allen BL, Leahy DJ, Hu P, Roessler E, Krauss RS, Muenke M (2017) BOC is a modifier gene in holoprosencephaly. Hum Mutat 10. ^1 2 3 4 {{cite journal |author=Croen, Lisa A. |author2=Shaw, Gary M. |author3=Lammer, Edward J. |year=2000 |title=Risk Factors For Cytogenetically Normal Holoprosencephaly in California: A Population-Based Case-Control Study |journal=American Journal of Medical Genetics|volume=90 |pages=320–325 | doi=10.1002/(SICI)1096-8628(20000214)90:4<320::AID-AJMG11>3.0.CO;2-8| pmid=10710231 |issue=4}} External links{{Medical resources| ICD10={{ICD10|Q|04|2|q|00}} | ICD9={{ICD9|742.2}} | ICDO= | OMIM=236100 | OMIM_mult= | MedlinePlus= | eMedicineSubj=radio | eMedicineTopic=347 | DiseasesDB=29610 | MeshID=D016142 | GeneReviewsNBK=NBK1530 | GeneReviewsName=Holoprosencephaly Overview | Orphanet=2162 }}
1 : Congenital disorders of nervous system |
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