Rubinstein-Taybi syndrome

Definition

Rubinstein-Taybi syndrome is a genetic disease characterized by broad thumbs and toes, short stature, distinctive facial features, and varying degrees of mental retardation.

Alternative Names

Rubinstein syndrome

Causes, incidence, and risk factors

Rubinstein-Taybi syndrome is a rare condition, affecting about 1 in 125,000 people. Most people with RTS have a defect in a gene that leads to an abnormal CREB binding protein (CREBBP).

About 10% of patients, typically with more severe problems, are missing the gene entirely and do not make any CREBBP.

Most cases are sporadic (not inherited) 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 just one parent passes on the defective gene, the child will be affected.

Symptoms

• Broadening of the thumbs and big toes
• Constipation
• Excess hair on body (hirsutism)
• Heart defects possibly requiring surgery (about 30% of patients)
• Mental retardation
• Seizures
• Short stature that is noticeable after birth
• Slow development of cognitive skills
• Slow development of motor skills accompanied by low muscle tone

Signs and tests

Examination and testing may reveal:

• Absent or extra kidney, and other problems with kidney or bladder
• An underdeveloped bone in the midface
• Narrow palate
• Crowded teeth
• Unsteady or stiff walking gait
• Downward-slanted eyes
• Low-set ears or malformed ears
• Drooping eyelid (ptosis)
• Cataracts
• Coloboma (a defect in the iris of the eye)
• Macrocephaly (excessively large head) or microcephaly (excessively small head)
• Narrow, small, or recessed mouth with crowded teeth
• Prominent or "beaked" nose
• 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
• Undescended testicle (cryptorchidism), or other testicular problems

Genetic tests can be done to determine 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

Rubinstein-Taybi Parents Group USA -- 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 depend on what the symptoms are. Feeding difficulties are common in infancy. Recurrent ear infections with hearing loss can result.

There may be abnormal heart structures at birth and abnormal heart rhythms.

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 couples with a family history of this disease who are planning a pregnancy.

References

Morelli JG. Disorders of the Nails. In: Kliegman RM, Behrman RE, Jenson HB, Stanton BF, eds. Nelson Textbook of Pediatrics. 18th Ed. Philadelphia, Pa: Saunders Elsevier; 2007: chap 662.