Pierre Robin sequence is characterized by an unusually small lower jaw (micrognathia) and downward displacement of the tongue (glossoptosis). Some infants also have an abnormal opening in the roof of the mouth (cleft palate); both the soft and hard palate can be affected.
The downward placement of the tongue, coupled with an unusually small jaw, may obstruct normal breathing and cause respiratory distress, feeding problems, and failure to thrive. Sleep disorders, including obstructive sleep apnea, a condition in which breathing temporarily stops, may occur.
Cardiovascular and lung conditions, such as benign heart murmurs, high blood pressure in the arteries of the lungs (pulmonary hypertension), and narrowing of the opening between the lung artery and the right ventricle of the heart (pulmonary stenosis) are possible manifestations of the disease. Anomalies of the musculoskeletal system, including those in the arms, legs, feet, and vertebral column, are also common. Inflammation of the middle ear (otitis media) occurs in about 80% of patients. Eye (ocular) defects are noted in about 10% to 30% of patients.
At present, the exact cause of Pierre Robin sequence is unknown. The most widely held view is that failure of the lower jaw to fully develop early in gestation causes the tongue to be positioned high in the oral cavity, which, in turn, prevents palate closure. The disease can occur by itself, and less commonly, as a feature in multiple defect disorders.
Pierre Robin sequence appearing with no underlying disorder may be inherited as an autosomal recessive trait. Genetic diseases are determined by the combination of genes for a particular trait that are on the chromosomes received from the father and the mother.
Recessive genetic disorders occur when an individual inherits the same abnormal gene for the same trait from each parent. If an individual receives one normal gene and one gene for the disease, he or she will be a carrier of the disease, but usually will not show symptoms. The risk of two carrier parents both passing the defective gene and having an affected child is 25% with each pregnancy. The risk of having a child who is a carrier like the parents is 50% with each pregnancy. The chance of having a child who receives normal genes from both parents and is genetically normal for that particular trait is 25%. The risk is the same for males and females.
All individuals carry 4-5 abnormal genes. Parents who are close relatives (consanguineous) have a higher chance than do unrelated parents of both carrying the same abnormal gene, which increases the risk of having children with a recessive genetic disorder.
Pierre Robin sequence affects males and females in equal numbers, with a prevalence of about one in 8,500 births.
Pierre Robin sequence can be detected while the fetus is still in the womb using ultrasound imaging.
Infants with Pierre Robin sequence should be observed closely for breathing difficulties. A tube may be inserted in the infant's throat (intubation) or a surgical opening may be made into the trachea through the neck (tracheostomy) to assist the infant in breathing.
Surgery to close the palate is typically performed between 12 and 18 months of age. Doctors may postpone the corrective surgery, however, to allow the opening in the palate to close on its own as natural growth occurs. If speech is impaired, a child with a cleft palate should participate in speech therapy or be monitored by a speech pathologist.
A child with a cleft palate is susceptible to fluid build-up in the ears, which can affect hearing and also lead to ear infections. Monitoring by an ear, nose and throat specialist and an audiologist is recommended for children with ear and hearing problems.
Surgery to improve the appearance of the jaw is rarely necessary because the small lower jaw seen at birth most often grows to a more normal size by 18 months of age.
Genetic counseling may be of benefit for patients and their families. Symptomatic and supportive treatment may also be useful.
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FROM THE INTERNET
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