Rubinstein-Taybi syndrome, also called Broad Thumb-Hallux syndrome, is a condition characterized by moderate to severe mental retardation, short stature, broad thumbs and first toes, distinctive facial features, and short stature. A distinction can be made between Rubinstein-Taybi like syndrome and Rubinstein-Taybi syndrome; the latter has gene promoter involvement.

Classical presentations of Rubinstein-Taybi syndrome include: mental disability/retardation (ranges from moderate to severe); broad thumbs and first toes; cryptorchidism in males; unusual face with oddly formed eyes, nose and palate; plus small stature (height), small head, and bone growth defects. Other symptoms of the disease vary. It is believed that patients with Rubinstein-Taybi syndrome have an increased risk of developing cancerous and noncancerous tumors, lymphoma, and leukemia.

Rubinstein-Taybi syndrome is a rare hereditary disease inherited via the autosomal dominant trait. Approximately 1 in 125,000 babies are born with Rubinstein-Taybi syndrome. Rubinstein-Taybi syndrome is caused by mutations in the CREBBP gene. The CREBBP gene is primarily responsible for producing CREB binding protein, a type of protein that regulates cell growth and is essential for normal fetal development. If a copy of the CREBBP gene is mutated, normal development is disrupted before and after birth, leading to classical signs of Rubinstein-Taybi syndrome. A small percentage of known cases are also associated with mutations in the EP300 gene, which result in the loss of one copy of the gene in each cell, leading to the reduction of amounts of p300 protein by half. The loss of one copy of EP300 gene leads to problems in normal fetal development.

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