![]() In humans, sexual dimorphism is a consequence of the XY sex-determination system. Since individuals with the condition have two cell lines of the opposite sex, it can also be considered an intersex condition. This is not to be confused with mosaicism or hybridism, neither of which are chimeric conditions. 46,XX/46,XY chimeras are the result of the merging of two non-identical twins. The cause of the condition lies in utero with the aggregation of two distinct blastocysts or zygotes (one of which expresses 46,XX and the other of which expresses 46,XY) into a single embryo, which subsequently leads to the development of a single individual with two distinct cell lines, instead of a pair of fraternal twins. ABS is a heterogeneous disorder and occurs with and without abnormal genitalia in both sexes.46,XX/46,XY is an exceptionally rare chimeric genetic condition characterized by the presence of some cells that express a 46,XX karyotype and some cells that express a 46,XY karyotype in a single human being. ABS is a multiple congenital anomaly syndrome characterized by craniosynostosis, radiohumeral synostosis, midface hypoplasia, malformed ears, arachnodactyly and multiple joint contractures. Craniosynostosis and severe syndactyly are not observed.ĭefects in FGFR2 are the cause of Antley-Bixler syndrome (ABS). In addition to these cardinal features, facial dysmorphism, malformations of the kidney and respiratory system and abnormal genitalia have been reported. LADDS is an autosomal dominant syndrome characterized by aplastic/hypoplastic lacrimal and salivary glands and ducts, cup-shaped ears, hearing loss, hypodontia and enamel hypoplasia, and distal limb segments anomalies. LADDS is a form of ectodermal dysplasia, a heterogeneous group of disorders due to abnormal development of two or more ectodermal structures. It is due to premature fusion of the sagittal suture or from external deformation.ĭefects in FGFR2 are a cause of lacrimo-auriculo-dento-digital syndrome (LADDS) also known as Levy-Hollister syndrome. Scaphocephaly is the most common of the craniosynostosis conditions and is characterized by a long, narrow head. FSPC is an autosomal dominant craniosynostosis syndrome characterized by scaphocephaly, macrocephaly, hypertelorism, maxillary retrusion, and mild intellectual disability. BSCGS is an autosomal dominant condition is characterized by the furrowed skin disorder of cutis gyrata, acanthosis nigricans, craniosynostosis, craniofacial dysmorphism, digital anomalies, umbilical and anogenital abnormalities and early death.ĭefects in FGFR2 are the cause of familial scaphocephaly syndrome (FSPC) also known as scaphocephaly with maxillary retrusion and mental retardation. ![]() Three subtypes of Pfeiffer syndrome have been described: mild autosomal dominant form (type 1) cloverleaf skull, elbow ankylosis, early death, sporadic (type 2) craniosynostosis, early demise, sporadic (type 3).ĭefects in FGFR2 are the cause of Beare-Stevenson cutis gyrata syndrome (BSCGS). PS is characterized by craniosynostosis (premature fusion of the skull sutures) with deviation and enlargement of the thumbs and great toes, brachymesophalangy, with phalangeal ankylosis and a varying degree of soft tissue syndactyly. ![]() Intellectual deficit is frequent and often severe, usually being associated with cerebral malformations.ĭefects in FGFR2 are a cause of Pfeiffer syndrome (PS) also known as acrocephalosyndactyly type V (ACS5). Syndactyly of the fingers and toes may be total (mitten hands and sock feet) or partial affecting the second, third, and fourth digits. The craniosynostosis is bicoronal and results in acrocephaly of brachysphenocephalic type. APRS is a syndrome characterized by facio-cranio-synostosis, osseous and membranous syndactyly of the four extremities, and midface hypoplasia. JWS is an autosomal dominant craniosynostosis syndrome characterized by craniofacial abnormalities and abnormality of the feet: broad great toes with medial deviation and tarsal-metatarsal coalescence.ĭefects in FGFR2 are a cause of Apert syndrome (APRS) also known as acrocephalosyndactyly type 1 (ACS1). CS is an autosomal dominant syndrome characterized by craniosynostosis (premature fusion of the skull sutures), hypertelorism, exophthalmos and external strabismus, parrot-beaked nose, short upper lip, hypoplastic maxilla, and a relative mandibular prognathism.ĭefects in FGFR2 are a cause of Jackson-Weiss syndrome (JWS). Defects in FGFR2 are the cause of Crouzon syndrome (CS) also called craniofacial dysostosis type I (CFD1).
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