- Epicanthus (HP:0000286): A fold of skin starting above the medial aspect of the upper eyelid and arching downward to cover, pass in front of and lateral to the medial canthus. Evidence: TAS. (OMIM:300979)
- Facial hypotonia (HP:0000297): Reduced muscle tone of a muscle that is innervated by the facial nerve (the seventh cranial nerve). Evidence: TAS. Frequency: 16/27. (OMIM:300979)
- Highly arched eyebrow (HP:0002553): Increased height of the central portion of the eyebrow, forming a crescent, semicircular, or inverted U shape. Evidence: TAS. (OMIM:300979)
- Tall stature (HP:0000098): A height above that which is expected according to age and gender norms. Evidence: PCS. Frequency: 3/28. (PMID:26443594)
- Delayed speech and language development (HP:0000750): A degree of language development that is significantly below the norm for a child of a specified age. Evidence: TAS. (OMIM:300979)
- Thick eyebrow (HP:0000574): Increased density/number and/or increased diameter of eyebrow hairs. Evidence: TAS. Frequency: 7/17. (OMIM:300979)
- Cerebellar hypoplasia (HP:0001321): Cerebellar hypoplasia is a descriptive term implying a cerebellum with a reduced volume, but a normal shape and is stable over time. Evidence: TAS. Frequency: Occasional (HP:0040283). (OMIM:300979)
- Hypoplasia of the corpus callosum (HP:0002079): Underdevelopment of the corpus callosum. Evidence: TAS. Frequency: Occasional (HP:0040283). (OMIM:300979)
- Short stature (HP:0004322): A height below that which is expected according to age and gender norms. Although there is no universally accepted definition of short stature, many refer to "short stature" as height more than 2 standard deviations below the mean for age and gender (or below the 3rd percentile for age and gender dependent norms). Evidence: TAS. Frequency: 6/28. (OMIM:300979)
- Seizure (HP:0001250): A seizure is an intermittent abnormality of nervous system physiology characterized by a transient occurrence of signs and/or symptoms due to abnormal excessive or synchronous neuronal activity in the brain. Evidence: PCS. Frequency: 10/31. (PMID:26443594)
- Global developmental delay (HP:0001263): A delay in the achievement of motor or mental milestones in the domains of development of a child, including motor skills, speech and language, cognitive skills, and social and emotional skills. This term should only be used to describe children younger than five years of age. Evidence: TAS. (OMIM:300979)
- Sleep disturbance (HP:0002360): An abnormal pattern in the quality, quantity, or characteristics of sleep. Evidence: TAS. (OMIM:300979)
- Malar flattening (HP:0000272): Underdevelopment of the malar prominence of the jugal bone (zygomatic bone in mammals), appreciated in profile, frontal view, and/or by palpation. Evidence: PCS. Frequency: 23/27. (PMID:26443594)
- Generalized hypotonia (HP:0001290): Generalized muscular hypotonia (abnormally low muscle tone). Evidence: TAS. (OMIM:300979)
- Sparse eyebrow (HP:0045075): Decreased density/number of eyebrow hairs. Evidence: TAS. (OMIM:300979)
- Thick vermilion border (HP:0012471): Increased width of the skin of vermilion border region of upper lip. Evidence: PCS. Frequency: 15/26. (PMID:26443594)
- Autistic behavior (HP:0000729): Persistent deficits in social interaction and communication and interaction as well as a markedly restricted repertoire of activity and interest as well as repetitive patterns of behavior. Evidence: PCS. Frequency: 4/15. (PMID:26443594)
- Anxiety (HP:0000739): Intense feelings of nervousness, tension, or panic often arise in response to interpersonal stresses. There is worry about the negative effects of past unpleasant experiences and future negative possibilities. Individuals may feel fearful, apprehensive, or threatened by uncertainty, and they may also have fears of falling apart or losing control. Evidence: TAS. (OMIM:300979)
- X-linked inheritance (HP:0001417): A mode of inheritance that is observed for traits related to a gene encoded on the X chromosome. Evidence: PCS. (PMID:26443594)
- Hyperactivity (HP:0000752): Hyperactivity is a condition characterized by constant and unusually high levels of activity, even in situations where it is deemed inappropriate. Evidence: TAS. (OMIM:300979)
- Intellectual disability (HP:0001249): The term intellectual disability or intellectual developmental disorder is used to describe significantly sub-average intellectual and adaptive functioning based on clinical assessment and as measured by individually administered, appropriately normed, standardized and validated tests of intellectual functioning and adaptive behavior, with onset during the developmental period from infancy through adolescence. Evidence: PCS. Frequency: 33/33. (PMID:26443594)
- Mandibular prognathia (HP:0000303): Abnormal prominence of the chin related to increased length of the mandible. Evidence: TAS. Frequency: 16/26. (OMIM:300979)
These phenotypes are associated with the disease Xq25 microduplication syndrome (OMIM:300979).