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Gene(s) | KMT2D (Type 1) | CBP (Type 1) | EHMT1 (Type 1*) |
 | KDM6A (Type 2) | EP300 (Type 2) | KMT2C (Type 2) |
Growth | Post-natal growth restriction | Post-natal growth delay with subsequent excessive weight gain during childhood | Markedly reduced linear growth and head circumference. Normal, reduced or increased weight. |
Craniofacial features | |||
Head size | Variable microcephaly | Microcephaly | Brachycephaly |
Eyes | Long palpebral fissures with eversion of the lateral one-third of the lower eyelid | Down-slanting palpebral fissures, long eye lashes | Hypertelorism |
Eyebrows | Arch eyebrows with notching/sparseness of the lateral portion | Highly arched eyebrows | Synophrys (long, single eye brow) |
Nose | Short columella with depressed nasal tip | Broad nasal bridge, beaked nose and prominent nasal septum extending below nares | Anteverted nares, macroglossia |
Mouth/Lips | Tented upper lip | Small opening of mouth | Tented cupid’s bow portion of upper lip |
Palate/Jaw | High arched palate with variable cleft, tooth abnormalities | High-arched palate with micrognathia | Prognathism |
Ears | Large prominent cupped ears | Low set auricles | Thick ear helices |
Cognitive and behavioral features | Mild to moderate intellectual disability with relative strength in verbal comprehension and more pronounced deficiencies in perceptual and nonverbal skills. Language and speech defects with expressive (dysarthria and dyspraxia) and expressive deficits. | Typically, moderate intellectual disability, ranging from mild to profound with relative weakness in working memory. Behavior characterized by high sociability but with challenges in communication, impulsivity, distraction, anxiety, and obsessive-compulsive attributes. Patients may also have mood disorders, tics and autistic behavior (more frequently in patients with CBP mutation vs EP300 mutation). | Mild, moderate or severe intellectual disability, language and delays, autistic behaviors, disordered sleeping, aggressive/hyperactive behaviors and auto-mutilatory behaviors |
Other features | Skeletal anomalies (brachymesophalangy, brachydactyly V, vertebral defects, 5th digit clinodactyly) and dermatoglyphic abnormalities (persistent fingertip pads), seizure disorders. Hypogammaglobulinemia, autoimmunity | Small opening of mouth | Skeletal features: kyphosis and scoliosis. Seizure disorders |