Rubinstein-Taybi syndrome (RTS)

Broad thumb   hallux syndrome

The Rubinstein-Taybi syndrome is a well-defined entity characterized by growth and mental retardation, broad thumbs and halluces, typical face, and various malformations.

The prevalence at birth was estimated to be 1 in 125,000 living newborn infants. RTS is caused by an autosomal dominant mutation.

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D012415

783 Rubinstein-Taybi syndrome

C0035934

The main clinical features of RTS are facial dysmorphism, broad thumbs, broad big toes, and growth and mental retardation.

The facial appearance is different in the newborn, but the most striking facial features in childhood include microcephaly, downslanting palpebral fissures, prominent and beaked nose with low nasal septum, highly arched palate, and mild micrognathia.

Broad thumbs and broad halluces are present in almost all cases. Other extremities abnormalities include angulation deformities of the thumbs and halluces, broad distal phalanges of other fingers, clinodactyly of the 5th finger, persistent fetal fingertip pads and overlapping toes.

Growth retardation is generally marked during infancy with feeding problems, and with a tendency to overweight in later childhood and adulthood. Constipation, recurrent upper respiratory infections and conjunctivitis are frequent problems in infancy.

Retarded motor and mental development become apparent in the first year of life. The average IQ of the patients is between 35 and 50, but some patients may have a better outcome. The performal IQ is higher than the verbal IQ.

Other findings may include eye abnormalities (tear duct obstruction, ptosis, strabismus, glaucoma, coloboma, cataract, refractive error), congenital heart defects (PDA, VSD, ASD), urinary tract malformations, specific dental abnormalities, epilepsy, and skin features (naevus flammeus, hirsutism, keloid scarring).

An increased risk for different tumors has been noticed. Tumors are reported in about 5 % of RTS patients. The reported tumors include brain tumors as meningioma, acute lymphocytic leukemia, pheochromocytoma, rhabdomyosarcoma (nasopharyngeal), and intraspinal neurilemmoma. An increased frequency of pilomatrixoma is also known in the syndrome.

There is no specific treatment in RTS.

Chromosome analysis is usually normal in RTS. Some cytogenetic rearrangements involving chromosome 16p13.3 have been described leading to the identification of the causing gene. An interstitial submicroscopic deletion of this region is found in approximately 12 % of the patients, using two-color FISH and the cosmid RT1 (D16S237).

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