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Craniofacial Conditions

 

Robin Sequence and Associated Syndromes

What is Robin sequence?

Robin sequence [spoken with a French pronunciation 'Row-BAN,' previously called "Pierre Robin syndrome"] begins with a lower jaw that is either too small (micrognathia) or is set back from the upper jaw (retrognathia ). This causes the tongue to be pushed backward in the throat, where it can flop back and block the airway ( glossoptosis). Most infants with Robin sequence also have a cleft palate.

What causes Robin sequence?

There are two potential causes: a failure of the lower jaw to develop or form properly (known as syndromic Robin sequence) or intrauterine pressure distorting the normal development of the jaw (known as deformational or nonsyndromic Robin sequence).

Normally, at seven to 10 weeks of pregnancy, the lower jaw grows rapidly and, before the roof of the mouth is sealed, the tongue descends into the mouth. Sometimes, in the womb, the lower jaw is too small so the tongue cannot descend, thus preventing the sides of the palate from fusing, resulting in a cleft palate. The small lower jaw causes the tongue to be positioned near the back of the mouth, potentially causing breathing and feeding problems at birth.

How common is Robin sequence?

It is relatively common, the frequency rates vary depending on how the condition is defined.

What are the chances that any future children will have the condition?

If you've had a child with syndromic Robin sequence, there is as high as 50 percent chance that a future child will have the condition as well. If your child has nonsyndromic Robin sequence, there is no inherited risk for future children to be affected.

What problems can I expect my child to have?

Robin sequence varies in severity. The most common problems for an infant with the disorder are breathing and eating difficulties. Your doctor or nurse can teach you the proper way to position your baby to minimize breathing problems. For severely affected infants, positioning alone may not be enough. Some children with a massive breathing problem may require a surgical procedure to ensure they take in enough air. Your child's doctor or an otolaryngologist (ear, nose, and throat specialist) will carefully monitor your baby for ear problems. Almost all children with a cleft palate have a risk of fluid build-up behind the eardrum. Ventilation tubes placed in the eardrum can relieve this problem.

How is Robin Sequence treated?

Often, the child's lower jaw (mandible), grows quickly during the first year of life -- such that by four to six years old, the profile looks normal. Children who will not exhibit this 'catch-up' growth may require an operation. The simple procedure is to release and advance the tongue and attach it to the lower jaw and lower lip. Another more complicated but effective procedure involves cutting the mandible and gradually pushing it forward (distraction osteoporosis). Rarely, an infant with Robin sequence may need a tracheostomy for breathing.

The cleft palate in an infant with Robin sequence is generally closed before the first birthday.

Do children with Robin sequence have abnormalities elsewhere in their body?

Sometimes they do. If so, the condition is designated syndromic Robin sequence.

There are more than 30 known syndromes associated with Robin sequence. The two most common are Stickler syndrome and velocardiofacial syndrome, also known as VFCS.

What is Stickler syndrome?

Stickler syndrome is the basis for about 30 to 40 percent of infants with Robin sequence. It is a disorder of the body's collagen -- the tissue that connects the bones, heart, eyes, and ears. It generally occurs in infants with no family history of the condition.

What problems do children with Stickler syndrome usually have?

The most common problem is nearsightedness, or myopia, which can be treated with corrective glasses. Some children have more severe eye problems, such as deterioration of the gel inside the eye, detachment of the retina, cataract, strabismus (eyes moving independently of each other), and, rarely, glaucoma. Any of these problems can lead to blindness.

Hearing problems can range from minor to severe -- even deafness in extreme cases. Many children experience bone and joint problems such as arthritis, curvature of the spine, joint pain, double-jointedness, and abnormalities at the ends of some bones. These kinds of problems tend to worsen with age. The heart problem most associated with Stickler syndrome is known as mitral valve prolapse, which occurs when a valve in the left side of the heart closes and protrudes into the lower chamber.

What causes Stickler syndrome?

Researchers have discovered that most people with the syndrome have a mutation in the three known genes that help produce collagen, a protein that gives tissues their structure.

How is Stickler syndrome treated?

Each child with Stickler syndrome has a unique set of problems. It is important that you meet with your child's care team to ensure that each problem area is treated in the appropriate manner at the proper time.

What is velocardiofacial syndrome?

Velocardiofacial syndrome (also called VCFS) occurs in about 15 percent of children with Robin sequence. It arises in approximately one in 2,000-5,000 newborns. Children with the condition have a long face with a somewhat prominent upper jaw, flat cheeks, and an underdeveloped lower jaw. Their eyelids often have a narrow opening, and their ears are small with somewhat thick upper rims. They often have a slightly prominent nose and a long, thin upper lip with a downward-slanting mouth. These facial differences are minor, and usually are not noticed. More than half of children with VCFS have a cleft palate, which causes abnormal speech.

More than 30 different problems have been associated with VCFS, although none of them occur in all children with VCFS. They include: cleft palate, usually of the soft palate (or hidden, submucous cleft palate); heart problems; minor facial abnormalities; learning difficulties; eye problems; feeding problems; middle-ear infections (otitis media); hypoparathyroidism (low levels of the parathyroid hormone that can result in seizures); difficulty in fighting infections (low levels of immune-globulins); muscle weakness; short height; and curvature of the spine (scoliosis). These problems are present at birth and do not worsen as children age.

Virtually all children with VCFS have some form of learning disability. Such difficulties are usually confined to certain well-defined areas, while in other areas their learning is normal.

About 10 percent of patients with VCFS have a condition known as DiGeorge sequence. These children are born without the thymus and parathyroid glands, placing them at increased risk of infections, low blood calcium, and delayed development. Usually this disorder improves as the child grows older.

What causes velocardiofacial syndrome?

The condition has been traced to a missing segment on chromosome 22. The error generally arises randomly in children with no family history of the disorder. It is known as an autosomal dominant condition, meaning that only one parent needs to have the gene for VCFS to pass it on to a child. When one parent has VCFS, the chance that his or her children will have the syndrome is about 50%. Most of the time, though, neither parent has the syndrome or carries the defective gene, and the cause of the genetic defect in the child is unknown.

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