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Table 1 Differences in the phenotypes of RSTS Type 1 (Caused by CREBBP mutations) and Type 2 (caused by EP300 mutations)

From: Rubinstein-Taybi syndrome in a Saudi boy with distinct features and variants in both the CREBBP and EP300 genes: a case report

Clinical Features Differences in the phenotypes
Facial dysmorphism - Both types have the following classic features [1,2,3,4,5,6,7,8,9,10,11,12]: highly- arched eyebrows, long eye lashes, broad nasal bridge, over-hanging columella, thin upper lip, pouting lower lip, posteriorly rotated ears, and micrognathia. These features tend to be milder in almost all cases of Type 2, and also in cases of Type 1 caused by missense mutations of the CREBBP gene [2, 11].
- The following features are common in Type 1 and are uncommon in Type 2: down-slanting of the palpebral fissures, and a grimacing smile [1, 12].
- Helical pits are occasionally seen in type 2 [12].
Intra-oral features - Talon cusps (an accessory cusp-like structure on the lingual side of the permanent incisors, resembling the shape of an eagle’s talon), and a highly-arched palate are common in both types. Bifid uvula and bifid tip of the tongue are rare features [8].
Mental/learning defects - intellectual disability is milder in Type 2 [2]. Learning disability without intellectual disability is frequently seen in Type 2 [12].
The hands/feet - Bilateral broadening of the thumbs/halluces is a feature of both types. However, the angulation of the thumbs/halluces are much less frequent in Type 2 [9]. Normal thumbs/halluces may be seen in Type 2 [10].
- The following occasional features are characteristic of Type 2: short first metatarsals, fetal finger tip pads (prominence of the ventral aspects of the finger tips), overlapping toes, syndactyly, and brachydactyly of the 5th toes [1, 4,5,6].
Other features - Seizures are more common in Type 1 [10]
- Microcephaly [9] and hirsutism [6] are more common in Type 2.
- Cardiac defects may be seen in both types.
- The following occasional features are characteristic of Type 1: patellar dislocation, reduced immunity (usually presenting as recurrent respiratory tract infections), undescended testes, and an increased risk of tumors of the nervous system [1,2,3, 11, 13].
- The following occasional features are characteristic of Type 2: scoliosis and swallowing difficulties [4, 5].
Preeclampsia of the mother during pregnancy - Seen in 23% of mothers of EP300 mutated patients compared to only 3% of mothers of CREBBP mutated patients [9].