Pierre Robin sequence (or syndrome) is a congenital condition that results in a combination of the following features which are present at the time of birth:
- a very small underdeveloped lower jaw (this is called micrognathia)
- cleft palate with the distinct absence of cleft lip, usually horseshoe or U-shaped
- a high arched palate
- a tongue that is placed very far back in the throat and can obstruct the airway causing difficulty breathing (glossoptosis)
- in about 10-15 percent of cases macroglossia (unusually large tongue), or ankyloglossia (tongue tie) may be present
- teeth present at the time of birth and dental malformations
- frequent ear infections
- temporary hearing loss from cleft palate causing fluid to collect in the ears
- nasal deformities (rare)
These abnormalities at the time of birth frequently lead to speech problems in children with Pierre Robin sequence. In 10-85 percent of cases other systemic manifestation may occur including:
- Eye problems (hypermetropia, myopia, astigmatism, corneal sclerosis, nasolacrimal duct stenosis)
- Cardiovascular problems have been documented in 5-58 percent of cases (benign heart murmur, patent ductus arteriosus, patent foramen ovale, atrial septal defect, and pulmonary hypertension)
- Musculoskeletal problems are noted frequently (70-80 percent of cases) and may include syndactyly, polydactyly, clinodactyly, and oligodactyly, clubfeet, hyperextensible joints, hip anomalies, knee anomalies, scoliosis, kyphosis, lordosis, and other abnormalities of the spine
- Abnormalities in the central nervous system are noted in approximately 50% of cases and may include: developmental delays, speech delays, hypotonia, and hydrocephalus.
- Genitourinary defects are rarer but may include undescended testes, hydronephrosis or hydrocele.
The incidence of Pierre Robin sequence is approximately 1 in 8500 births, affecting males and females equally. Pierre Robin sequence can occur in and of itself but is associated with a number of other genetic conditions including Stickler syndrome, CHARGE syndrome, Shprintzen syndrome, Mobius syndrome, trisomy 18 syndrome, trisomy 11q syndrome, deletion 4q syndrome, and others.
There are a few theories as to what causes Pierre Robin sequence. The first is that mandibular hypoplasia occurs during the 7-11th week of pregnancy. This results in the tongue remaining high in the oral cavity preventing closure of the palatal shelves and causing a U-shaped cleft palate. A decreased amount of amniotic fluid may be a factor.
The second theory is that there is a delay in the neurological development of the tongue musculature, pharyngeal pillars, and the palate accompanied by a delay in hypoglossal nerve conduction. This theory explains why many symptoms resolve by about 6 years of age.
The third theory is that a major problem occurs during development that results in dysneurulation of the rhombencephalus (the hindbrain — the portion of the brain containing the brainstem and cerebellum).
Finally, when Pierre Robin sequence occurs without any other anomaly disorders, a DNA mutation that reduces the activity of a gene called SOX9 may be to blame. The SOX9 protein aids in skeletal development and less of it may contribute to the craniofacial abnormalities in Pierre Robin sequence.
There is no cure for Pierre Robin sequence. Management of the condition involves treating individual symptoms. In most cases, the lower jaw grows rapidly during the first year of life and usually appears normal by about kindergarten. Natural growth also often cures any respiratory (airway) problems that may be present. Sometimes an artificial airway (such as a nasopharyngeal or oral airway) needs to be used for a period of time. Cleft palate must be repaired surgically as it can cause problems with feeding or breathing. Many children with Pierre Robin sequence will require speech therapy.
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The severity of Pierre Robin sequence varies greatly between individuals as some people may only have a couple of the symptoms associated with this condition while others may have many of the associated symptoms. Cardiovascular or central nervous symptoms may also be more difficult to manage than some of the craniofacial abnormalities associated with Pierre Robin sequence. Studies have shown that isolated Pierre Robin sequence, (when the condition occurs without another associated syndrome), does not usually increase mortality risk, particularly where cardiovascular or central nervous system problems are not present.