If one copy of the CREBBP gene is deleted or mutated, cells make only half of the normal amount of CREB binding protein. A reduction in the amount of this protein disrupts normal development before and after birth, leading to the signs and symptoms of Rubinstein–Taybi syndrome.Mutations in the EP300 gene are responsible for a small percentage of cases of Rubinstein–Taybi syndrome. These mutations result in the loss of one copy of the gene in each cell, which reduces the amount of p300 protein by half. Some mutations lead to the production of a very short, nonfunctional version of the p300 protein, while others prevent one copy of the gene from making any protein at all. Although researchers do not know how a reduction in the amount of p300 protein leads to the specific features of Rubinstein–Taybi syndrome, it is clear that the loss of one copy of the EP300 gene disrupts normal development.A mouse model has been identified in order to perform experimental research procedures. The model has exhibited the same clinical symptoms seen in humans and has become a foundation for future research.Unfortunately, in nearly 40% of cases, neither gene, CREBBP or EP300, can be implicated in the cause of the disease. In these cases, there is no mutation on the 16th chromosome leaving many more questions yet to be answered.
Rubinstein–Taybi syndrome (RTS) is a rare genetic condition characterized by short stature, moderate to severe learning difficulties, distinctive facial features, and broad thumbs and first toes. Other features of the disorder vary among affected individuals. These characteristics are caused by a mutation or deletion in the CREBBP and/or EP300 gene located on chromosome 16. People with this condition have an increased risk of developing noncancerous and cancerous tumors, leukemia, and lymphoma. This condition is sometimes inherited as an autosomal dominant pattern and is uncommon. Many times it occurs as a de novo (not inherited) occurrence. It occurs in an estimated 1 in 125,000-300,000 births. Presentation
Rubinstein–Taybi syndrome presents itself from birth, and is usually hallmarked by delayed physical and cognitive growth.Typical features of the disorder include:

Broad thumbs and broad first toes and clinodactyly of the 5th finger
Mental disability
Small height, low bone growth, small head
Cryptorchidism in males
Unusual facies involving the eyes, nose, and palate
Anesthesia may be dangerous in these patients: "According to the medical literature, in some cases, individuals with Rubinstein–Taybi syndrome may have complications (e.g., respiratory distress and/or irregular heart beats [cardiac arrythmias]) associated with a certain muscle relaxant (succinylcholine) and certain anesthesia. Any situations requiring the administration of anesthesia or succinylcholine (e.g., surgical procedures) should be closely monitored by skilled professionals (Anesthesiologists)." Primary literature suggests the children may have a higher rate of cardiac physical and conduction abnormalities which may cause unexpected results with cardioactive medications.