![]() ![]() The palatal cleft is often U-shaped and wider than that observed in other people with cleft palate. The infant usually has respiratory difficulty, especially when supine. PRS is generally diagnosed clinically shortly after birth. Disorders associated with PRS include Stickler syndrome, DiGeorge syndrome, fetal alcohol syndrome, Treacher Collins syndrome, and Patau syndrome. PRS may occur in isolation, but it is often part of an underlying disorder or syndrome. Some evidence suggests that genetic dysregulation of the SOX9 gene (which encodes the SOX-9 transcription factor) and/or the KCNJ2 gene (which encodes the Kir2.1 inward-rectifier potassium channel) impairs the development of certain facial structures, which can lead to PRS. Specifically, mutations at chromosome 2 (possibly at the GAD1 gene), chromosome 4, chromosome 11 (possibly at the PVRL1 gene), or chromosome 17 (possibly at the SOX9 gene or the KCNJ2 gene) have all been implicated in PRS. In the case of PRS which is due to a genetic disorder, a hereditary basis has been postulated, but it usually occurs due to a de-novo mutation. Genetic basis Īlternatively, PRS may also be caused by a genetic disorder. After the child is born, the mandible continues to grow until the child reaches maturity. At birth, however, the mandible is still much smaller (hypoplastic) than it would have been with normal development. Later in gestation (at around 12 to 14 weeks), extension of the neck of the fetus releases the pressure on the mandible, allowing it to grow normally from this point forward. This condition manifests as a cleft palate. This in turn may result in failure of the left and right palatal shelves to fuse in the midline to form the hard palate. With nowhere else to go, the base of the tongue is downwardly displaced, which causes the tip of the tongue to be interposed between the left and right palatal shelves. The concave space formed by the body of the hypoplastic mandible is too small to accommodate the tongue, which continues to grow unimpeded. ![]() This compression of the chin interferes with development of the body of the mandible, resulting in micrognathia. ![]() One theory for the etiology of PRS is that, early in the first trimester of gestation, some mechanical factor causes the neck to be abnormally flexed such that the tip of the mandible becomes compressed against the sternoclavicular joint. The physical craniofacial deformities of PRS may be the result of a mechanical problem in which intrauterine growth of certain facial structures is restricted, or mandibular positioning is altered. Hearing loss and speech difficulty are often associated with PRS. Cleft palate (incomplete closure of the roof of the mouth) is present in the majority of patients. PRS is characterized by an unusually small mandible, posterior displacement or retraction of the tongue, and upper airway obstruction. Signs and symptoms Micrognathism in Pierre Robin sequence Cleft palate in Pierre Robin sequence PRS is not merely a syndrome, but rather it is a sequence-a series of specific developmental malformations which can be attributed to a single cause. A wide, U-shaped cleft palate is commonly also present. The three main features are micrognathia (abnormally small mandible), which causes glossoptosis (downwardly displaced or retracted tongue), which in turn causes breathing problems due to obstruction of the upper airway. Pierre Robin sequence ( / p j ɛər r ɔː ˈ b æ̃/ abbreviated PRS) is a congenital defect observed in humans which is characterized by facial abnormalities. Intrauterine compression of fetal mandible or de-novo mutations (on chromosomes 2, 4, 11, or 17)Ĭraniofacial surgery, oral and maxillofacial surgery Micrognathia, glossoptosis, obstruction of the upper airway, sometimes cleft palate Pierre Robin syndrome, Pierre Robin malformation, Pierre Robin anomaly, Pierre Robin anomalad ![]()
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