Genetics Northern California

Pierre Robin Sequence

Pierre Robin sequence (or syndrome) is a congenital disorder that presents as a group of problems including a wide U-shaped cleft palate, a small, recessed lower jaw (micrognathia), and some degree of airway obstruction due to a downwardly displaced tongue (glossoptosis).

Different people will refer to this particular disorder as either Pierre Robin sequence or Pierre Robin syndrome. Although the two names are used interchangeably, there is a slight difference between a sequence and a syndrome that requires clarification.

A syndrome is a condition recognized by multiple factors that are present and related to the same genetic condition. A sequence, on the other hand, is a pattern of problems that are believed to have occurred from a single event. Although the causes of Pierre Robin are not entirely understood, the features appear to be the results of a series of events - thus making it a sequence. Until more information is gained, however, the term syndrome cannot be entirely ruled out.

Pierre Robin sequence varies from child to child. Quite often, breathing difficulties are a serious problem for affected children. Because the tongue is seated back in the mouth cavity, it tends to fall back and block the airway. This can be very dangerous for a child if he or she is not receiving enough oxygen to the brain. Feeding problems are usually related to these breathing difficulties. Because affected children have to work overtime to get the oxygen they need, food and liquids tend to make it more difficult for the children to obtain enough oxygen. Their bodies expend an unusually high number of calories doing so; this often leads to weight loss and a failure to thrive.

Other common difficulties affected children face include reflux (due to negative pressure created within the chest cavity from obstructed airways), ear infections (as a result of the cleft palate), frequent colds, oral defensiveness (as a result of reduced oral stimulation from extended tube feeding), speech problems, and overcrowded teeth. In 14% of cases, children with Pierre Robin have congenital heart disease.

Cause
The causes for the disorder are not entirely understood. However, poor development of the lower jaw during the 6th to 11th week of fetal life seems to be a likely explanation. For reasons yet unclear, the head of the fetus does not rise off the chest causing forward growth of the lower jaw to be restricted. The tongue, as a result, remains back in the mouth cavity and becomes forced up into the roof of the mouth. Thus, the palate is not able to fuse and the child will be born with a cleft palate.

Why this sequence of events occurs is not clearly understood. There is no evidence that prenatal exposure or inter-utero trauma is related to the disorder. Pierre Robin sequence may be an isolated finding or it can sometimes be part of a genetic syndrome or chromosomal abnormality. Stickler syndrome, Treacher Collins syndrome, Velocardiofacial syndrome, and fetal alcohol syndrome are a few of the conditions that sometimes exhibit the features characteristic of Pierre Robin.

Diagnosis
The diagnosis of Pierre Robin sequence or syndrome is made based on the clinical findings described in the definition above.

Treatment/Services
Infants and children with Pierre Robin sequence need to be evaluated and managed by a Craniofacial Team for planning and implementation of treatment. A number of the clinical features of Pierre Robin sequence (PRS) can be treated through certain therapies and/or surgeries. The most significant and immediate consideration in PRS addressed immediately is the airway to determine the degree of breathing difficulty. The jaw may surgically need to be brought forward over a given period of time in order for the airway to be more open (mandibular distraction). A tracheostomy may need to be done (a tube is placed in the windpipe (trachea) to provide an adequate airway), or a tongue-lip adhesion may be done (a method of keeping the tongue from blocking the airway). In less severe cases, simply positioning the child on his or her stomach will prevent the tongue from falling back.

Adequate growth may be problematic for an infant with PRS because of the small jaw and tongue placement interfering with adequate feeding by mouth. An attempt to feed an infant with special bottles is made. However, if feeding by mouth is not possible, a feeding tube placed directly into the stomach (G-tube or gastrostomy tube) will need to be done. A referral to a feeding specialist will need to be made in order that an oral stimulation program may be developed and implemented for the purpose of working towards a long-term goal of oral feeding.

Cleft palate repair can usually be performed within the first few years of life. During this surgery, ear tubes are commonly placed if the young child has had ear infections. A speech evaluation will be done by a craniofacial speech pathologist a few months following surgery of the palate. Speech therapy may be instituted through early intervention programs or the school district. Because the child with a cleft palate is at risk for increased ear infections, hearing tests need to be performed regularly. Orthodontic treatment and jaw surgery may be a consideration for future treatment.