- Microcephaly (HP:0000252): Head circumference below 2 standard deviations below the mean for age and gender. Evidence: TAS. Frequency: Very frequent (HP:0040281). (ORPHA:3307)
- Abnormality of the face (HP:0000271): An abnormality of the face. Evidence: TAS. Frequency: Very frequent (HP:0040281). (ORPHA:3307)
- Long philtrum (HP:0000343): Distance between nasal base and midline upper lip vermilion border more than 2 SD above the mean. Alternatively, an apparently increased distance between nasal base and midline upper lip vermilion border. Evidence: TAS. Frequency: Very frequent (HP:0040281). (ORPHA:3307)
- Abnormality of neuronal migration (HP:0002269): An abnormality resulting from an anomaly of neuronal migration, i.e., of the process by which neurons travel from their origin to their final position in the brain. Evidence: TAS. Frequency: Very frequent (HP:0040281). (ORPHA:3307)
- 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. Frequency: Frequent (HP:0040282). (ORPHA:3307)
- Narrow mouth (HP:0000160): Distance between the commissures of the mouth more than 2 SD below the mean. Alternatively, an apparently decreased width of the oral aperture (subjective). Evidence: TAS. Frequency: Occasional (HP:0040283). (ORPHA:3307)
- Thin vermilion border (HP:0000233): Height of the vermilion of the medial part of the lip more than 2 SD below the mean, or apparently reduced height of the vermilion of the lip in the frontal view. The vermilion is the red part of the lips (and confusingly, the vermilion itself is also often referred to as being equivalent the lips). Evidence: TAS. Frequency: Occasional (HP:0040283). (ORPHA:3307)
- Facial asymmetry (HP:0000324): An abnormal difference between the left and right sides of the face. Evidence: TAS. Frequency: Occasional (HP:0040283). (ORPHA:3307)
- Downslanted palpebral fissures (HP:0000494): The palpebral fissure inclination is more than two standard deviations below the mean. Evidence: TAS. Frequency: Occasional (HP:0040283). (ORPHA:3307)
- Large hands (HP:0001176). Evidence: TAS. Frequency: Occasional (HP:0040283). (ORPHA:3307)
- 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: TAS. Frequency: Occasional (HP:0040283). (ORPHA:3307)
- 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: TAS. Frequency: Occasional (HP:0040283). (ORPHA:3307)
- Syncope (HP:0001279): A transient loss of consciousness (i.e., characterized by a rapid onset, a short duration, and a spontaneous and complete recovery) due to cerebral hypoperfusion. Evidence: TAS. Frequency: Occasional (HP:0040283). (ORPHA:3307)
- Gait disturbance (HP:0001288): The term gait disturbance can refer to any disruption of the ability to walk. Evidence: TAS. Frequency: Occasional (HP:0040283). (ORPHA:3307)
- Achalasia (HP:0002571): A disorder of esophageal motility characterized by the inability of the lower esophageal sphincter to relax during swallowing and by inadequate or lacking peristalsis in the lower half of the body of the esophagus. Evidence: TAS. Frequency: Occasional (HP:0040283). (ORPHA:3307)
- Scoliosis (HP:0002650): The presence of an abnormal lateral curvature of the spine. Evidence: TAS. Frequency: Occasional (HP:0040283). (ORPHA:3307)
- Short nose (HP:0003196): Distance from nasion to subnasale more than two standard deviations below the mean, or alternatively, an apparently decreased length from the nasal root to the nasal tip. Evidence: TAS. Frequency: Occasional (HP:0040283). (ORPHA:3307)
- Posteriorly rotated ears (HP:0000358): A type of abnormal location of the ears in which the position of the ears is characterized by posterior rotation (the superior part of the ears is rotated towards the back of the head, and the inferior part of the ears towards the front). Evidence: TAS. Frequency: Frequent (HP:0040282). (ORPHA:3307)
These phenotypes are associated with the disease Tetrasomy 18p syndrome (ORPHA:3307).