Rubinstein-Taybi syndrome. Broad thumb-hallux syndrome.
Incidence
RSTS is inherited in an autosomal dominant manner. In most instances, the parents of an individual with RSTS are not affected. The disease is a rare genetic disorder with a prevalence of 1:250,000 live births. The syndrome is usually sporadic. One gene has been localized and identified on chromosome 16p13.3 (CBP gene). Most cases are due to new mutations.
Clinical Characteristics
Rubinstein-Taybi syndrome (RSTS) is characterized by distinctive facial features, broad and often angulated thumbs and first toes, short stature, and moderate-to-severe mental retardation. The characteristic craniofacial features are downslanting palpebral fissures, columella extending below the nares, and highly arched palate. Prenatal growth is often normal; however, height, weight, and head circumference percentiles rapidly drop in the first few months of life. IQ scores range from 25 to 79; average IQ is between 36 and 51. Other findings that are variable include coloboma, cataract, congenital heart defects, renal abnormalities, and cryptorchidism. RSTS is frequently recognized at birth or in infancy because of the striking facial features and characteristic hand and foot findings. Problems in early life include respiratory difficulties, feeding problems, poor weight gain, recurrent infections, and severe constipation.
Precipitants
None. Keep in mind that cardiac arrhythmia can occur with use of succinylcholine. Laryngeal wall collapsibility may produce sleep and anesthesia problems.
Provocation Tests
None
Diagnostic Procedures
The diagnosis of RSTS is primarily based on clinical features. FISH analysis of the CREBBP gene is available on a clinical basis and detects microdeletions in approximately 10% of individuals with RSTS. Mutation scanning is available clinically but mutation detection rates are unknown. Other types of molecular genetic testing, available on a research basis only, detect mutations in another 35% of affected individuals.