Rubinstein-Taybi syndrome

Definition

Rubinstein-Taybi syndrome is a genetic disease characterized by mental deficiency, broad thumbs and toes, short stature, and characteristic facial features.

Causes, incidence, and risk factors

Rubinstein-Taybi syndrome (RTS) is a rare condition, affecting about 1 in 125,000 people. The gene involved in RTS, which is called CREB binding protein (CREBBP), was identified in 1995.

Most patients have mutations in the gene, resulting in an abnormal CREB binding protein. About 10% of patients, typcially with more severe problems, have an outright deletion of the gene and they do not make any of the protein.

Most cases are sporadic and likely due to a new mutation occurring during fetal development, which was not passed on by either parent. However, in some cases, it is inherited in an autosomal dominant fashion, which means that if one parent passes on the defective gene, the child will be affected.

The classic feature is broad thumbs and great toes, but typically there is also short stature, unusual face, low-set ears, port-wine-stain, undescended testicles in the male, and downward slant of the eyes.

Symptoms

• Broad thumbs and great toes
• Slow development of both cognitive and motor skills with low muscle tone
• Mental retardation
• Short stature that is noticeable after birth
• Excess hair on body (hirsutism)
• Heart defects possibly requiring surgery (about 40% of patients)  
• Constipation

Signs and tests

• Hypoplastic (underdeveloped) maxilla (bone in the midface), narrow palate, crowded teeth
• An unsteady or stiff walking gait
• Downward-slanted eyes
• Low-set ears or malformed ears
• Drooping eyelid (ptosis )
• Cataract
• Coloboma (a defect in the iris of the eye)
• Cryptorchidism or other testicular problems
• Macrocephaly (excessively large head) or microcephaly (excessively small head)
• Skeletal (limb) abnormalities including the last segment of the other fingers and toes, appearing broad on x-rays or physical examination
• Thick and arched eyebrows with long eyelashes
• Narrow, small, or recessed mouth with crowded teeth
• Prominent or "beaked" nose
• Absent or extra kidney, and other problems with kidney or bladder
• Genetic or mutation testing, including deletion testing to see if the CREBBP gene is missing

Treatment

There is no specific treatment for Rubinstein-Taybi syndrome. Symptoms such as mental retardation are treated as necessary with speech and cognitive therapy. Surgical repair of thumbs or great toes can sometimes improve grasp or relieve discomfort. Treatment may not be necessary in all cases.

Support Groups

Additional resources are available from the Rubinstein-Taybi Parents Group USA. Call 888-447-2989. www.rubinstein-taybi.org

Expectations (prognosis)

The majority of children can learn to read at an elementary level. The majority have delayed motor development, but on average, they learn to walk by 2 1/2 years of age.

Complications

• Complications vary depending on the symptoms that are present.
• Feeding difficulties are common in infancy.
• Recurrent ear infections with hearing loss can result.
• Abnormal heart structures at birth and abnormal heart rhythms have been reported.
• There is an increased risk for keloid formation of the skin.

Calling your health care provider

Call for an appointment with your health care provider if you child does not seem to be developing normally. An appointment with a geneticist is appropriate if the provider finds signs of Rubinstein-Taybi syndrome such as broad thumbs and toes.

Prevention

Genetic counseling is advised for parents with a family history of this disease who are planning a pregnancy.

Illustrations

Polydactyly - an infant's hand

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Rubinstein syndrome ; rubinstein taybi syndrome; rubinstein syndrome