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Rubinstein-Taybi syndrome

Also known as: Broad Thumb-great Toe syndrome

Background

Rubinstein-Taybi syndrome (RTS) is a rare genetic condition, characterised by distinctive facial and physical differences. The most striking physical feature is broad, sometimes angulated thumbs and first toes. The facial features vary with age and include a prominent nose, full lower lip and down-slanting eyes. Undescended testes occur in males. Other variable features include congenital (present from birth) heart disease and kidney abnormalities, eye and hearing problems, increased keloid (scar tissue) formation, unusually shaped teeth, feeding difficulties in infancy, short stature and constipation Seizures may occur. There is a small increase in the chance of developing tumours (mainly leukaemia). 

Credits

Last updated October 2019 by Dr Zerin Hyder, Clinical Genetics Specialty Trainee, and reviewed by Dr Siddharth Banka, Consultant Clinical Geneticist at St Mary's Hospital, Manchester, UK.

Although great care has been taken in the compilation and preparation of all entries to ensure accuracy, we cannot accept responsibility for any errors or omissions. Any medical information provided is for education/information purposes and is not designed to replace medical advice by a qualified medical professional.

What are the symptoms?

Children with RTS usually have a normal birth weight, but subsequent growth is poor, with most children being of short stature with a small head size. Problems that may occur in early life include breathing difficulties, feeding problems, poor weight gain, recurrent infections, and constipation.

Developmental delay occurs in most children with RTS. Most people have moderate to severe learning difficulties, although a few have mild learning difficulties (see entry Learning Disability). They may have particular problems with expressive language and often benefit from using sign language. Most children become self-sufficient in eating, dressing and toileting.

Usually individuals with RTS have friendly and sociable personalities; however, many will find change in routine difficult and show signs of autistic behaviour. Other behavioural problems may include poor concentration, reduced tolerance to noise and crowds, impulsive behaviour, instability of mood and high pain tolerance. Some will show self-stimulatory behaviours, such as rocking and hand-flapping.

Individuals with RTS tend to be shorter than average and often become overweight. This can contribute to sleep apnoea (difficulty breathing when asleep), which they are prone to due to having a narrow palate, micrognathia (small chin) and hypotonia (floppiness).

What are the causes?

Changes in two genes are known to cause RTS. The changes occur by chance and are not caused by anything that is done or not done during pregnancy. A change in the CREBBP gene is found in 50-60% of affected individuals, and in the EP300 gene in approximately 10% of affected individuals. Some cases of RTS are caused by a small missing piece (deletion) of genetic material from chromosome 16. Many genes, including CREBBP, are missing as a result of this deletion. This is thought to account for cases of RTS that are associated with more serious complications.

Approximately 30% of people with RTS do not have a gene change in CREBBP, EP300 or a deletion in chromosome 16. In these cases, the cause of RTS is unknown, but researchers predict that changes in other genes are responsible for the condition.

More recently, specific gene changes in CREBBP and EP300 have been also reported in association with a condition that is distinct from RTS, called Menke-Hennekam syndrome. This condition has a very different set of signs and symptoms to RTS.

How is it diagnosed?

Normally RTS can be recognised in a baby or child by the characteristic facial features, broad thumbs and great toes and other symptoms consistent with the diagnosis. The diagnosis can be confirmed by genetic testing in up to 70% of affected individuals.

How is it treated?

The management of RTS is directed towards identifying the specific problems an individual has and treating them as appropriate, for example, treatment of heart problems or hearing difficulties. There is no cure for the condition. Individuals will need to be managed by a multidisciplinary team of specialists who can help support their medical, educational and social care needs.

Inheritance patterns and prenatal diagnosis

Inheritance pattern
RTS is a genetic disorder that usually affects only one person in the family. If a genetic test identifies the cause in an affected person, parents can be tested. The risk of recurrence is very low, and even if testing the parents is not possible; the chance of a second affected child is around 1%.  If an individual with RTS has children of their own, the chance for a similarly affected child may be as high as 50%.

Prenatal diagnosis
If the genetic change is known in an affected child, prenatal diagnosis may be possible to reassure parents.

Is there support?

Rubinstein Taybi Syndrome Support Group

Email: info@rtsuk.org.uk
www.rtsuk.org.uk

The Group is a Registered Charity in England and Wales No. 1147765, established in 1986. It offers support to families and linking with others where possible. It has an area family network, publishes a newsletter twice a year and has an information leaflet available. The Group supports over 200 families and holds two family events a year.

Group details last reviewed November 2019.