- 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. Frequency: Very frequent (HP:0040281). (ORPHA:544254)
- 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: Very frequent (HP:0040281). (ORPHA:544254)
- 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. Frequency: Very frequent (HP:0040281). (ORPHA:544254)
- Generalized-onset seizure (HP:0002197): A generalized-onset seizure is a type of seizure originating at some point within, and rapidly engaging, bilaterally distributed networks. The networks may include cortical and subcortical structures but not necessarily the entire cortex. Evidence: TAS. Frequency: Very frequent (HP:0040281). (ORPHA:544254)
- Abnormality of pain sensation (HP:0010832): Pain is an unpleasant sensation that can range from mild, localized discomfort to agony, whereby the physical part of pain results from nerve stimulation and is often accompanied by an emotional component. This term groups abnormalities in pain sensation presumed to result from abnormalities related to the specific nerve fibers that carry the pain impulses to the brain. Evidence: TAS. Frequency: Very frequent (HP:0040281). (ORPHA:544254)
- Atypical behavior (HP:0000708): Atypical behavior is an abnormality in a person's actions that can be controlled or modulated by the will of the individual. While abnormal behaviors can be difficult to control, they are distinct from other abnormal actions that cannot be affected by the individual's will. Evidence: TAS. Frequency: Frequent (HP:0040282). (ORPHA:544254)
- 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: TAS. Frequency: Frequent (HP:0040282). (ORPHA:544254)
- Ataxia (HP:0001251): Ataxia refers to impaired coordination of voluntary muscle movement. Cerebellar ataxia refers to ataxia due to dysfunction of the cerebellum. This causes a variety of elementary neurological deficits including asynergy (lack of coordination between muscles, limbs and joints), dysmetria (lack of ability to judge distances that can lead to under- or overshoot in grasping movements), and dysdiadochokinesia (inability to perform rapid movements requiring antagonizing muscle groups to be switched on and off repeatedly). Evidence: TAS. Frequency: Frequent (HP:0040282). (ORPHA:544254)
- Hypotonia (HP:0001252): Hypotonia is an abnormally low muscle tone (the amount of tension or resistance to movement in a muscle). Even when relaxed, muscles have a continuous and passive partial contraction which provides some resistance to passive stretching. Hypotonia thus manifests as diminished resistance to passive stretching. Hypotonia is not the same as muscle weakness, although the two conditions can co-exist. Evidence: TAS. Frequency: Frequent (HP:0040282). (ORPHA:544254)
- Gait disturbance (HP:0001288): The term gait disturbance can refer to any disruption of the ability to walk. Evidence: TAS. Frequency: Frequent (HP:0040282). (ORPHA:544254)
- Abnormal facial shape (HP:0001999): An abnormal morphology (form) of the face or its components. Evidence: TAS. Frequency: Frequent (HP:0040282). (ORPHA:544254)
- Moderate intellectual disability (HP:0002342): Moderate intellectual disability (ID) is defined as a type of ID characterized by moderately sub-average adaptive functioning and intellectual functioning, with an intelligence quotient (IQ) the range of 35-49. Evidence: TAS. Frequency: Frequent (HP:0040282). (ORPHA:544254)
- Sleep disturbance (HP:0002360): An abnormal pattern in the quality, quantity, or characteristics of sleep. Evidence: TAS. Frequency: Frequent (HP:0040282). (ORPHA:544254)
- Incoordination (HP:0002311): A deficit in coordination of muscle movements. Coordination is defined as the orchestrated movement of multiple body parts as required to accomplish intended actions, like walking. Evidence: TAS. Frequency: Frequent (HP:0040282). (ORPHA:544254)
- Developmental regression (HP:0002376): Loss of developmental skills, as manifested by loss of developmental milestones. Evidence: TAS. Frequency: Frequent (HP:0040282). (ORPHA:544254)
- Poor speech (HP:0002465). Evidence: TAS. Frequency: Frequent (HP:0040282). (ORPHA:544254)
- Severe intellectual disability (HP:0010864): Severe intellectual disability (ID) is defined as a type of ID characterized by severely sub-average adaptive functioning and intellectual functioning, with an intelligence quotient (IQ) the range of 20-34. Evidence: TAS. Frequency: Frequent (HP:0040282). (ORPHA:544254)
- Eating-induced seizure (HP:0020208): A seizure precipitated by aspects of anticipating food, eating itself, or the post-prandial period. Evidence: TAS. Frequency: Frequent (HP:0040282). (ORPHA:544254)
- Abnormal eating behavior (HP:0100738): Abnormal eating habits involve excessive or insufficient consumption of food, or any other abnormal pattern of food consumption. Evidence: TAS. Frequency: Frequent (HP:0040282). (ORPHA:544254)
- Hypospadias (HP:0000047): Abnormal position of urethral meatus on the ventral penile shaft (underside) characterized by displacement of the urethral meatus from the tip of the glans penis to the ventral surface of the penis, scrotum, or perineum. Evidence: TAS. Frequency: Occasional (HP:0040283). (ORPHA:544254)
- Wide mouth (HP:0000154): Distance between the oral commissures more than 2 SD above the mean. Alternatively, an apparently increased width of the oral aperture (subjective). Evidence: TAS. Frequency: Occasional (HP:0040283). (ORPHA:544254)
- 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:544254)
- High palate (HP:0000218): Height of the palate more than 2 SD above the mean (objective) or palatal height at the level of the first permanent molar more than twice the height of the teeth (subjective). Evidence: TAS. Frequency: Occasional (HP:0040283). (ORPHA:544254)
- 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:544254)
- Microcephaly (HP:0000252): Head circumference below 2 standard deviations below the mean for age and gender. Evidence: TAS. Frequency: Occasional (HP:0040283). (ORPHA:544254)
- Long face (HP:0000276): Facial height (length) is more than 2 standard deviations above the mean (objective); or, an apparent increase in the height (length) of the face (subjective). Evidence: TAS. Frequency: Occasional (HP:0040283). (ORPHA:544254)
- Triangular face (HP:0000325): Facial contour, as viewed from the front, triangular in shape, with breadth at the temples and tapering to a narrow chin. Evidence: TAS. Frequency: Occasional (HP:0040283). (ORPHA:544254)
- Macrotia (HP:0000400): Median longitudinal ear length greater than two standard deviations above the mean and median ear width greater than two standard deviations above the mean (objective); or, apparent increase in length and width of the pinna (subjective). Evidence: TAS. Frequency: Occasional (HP:0040283). (ORPHA:544254)
- Deeply set eye (HP:0000490): An eye that is more deeply recessed into the plane of the face than is typical. Evidence: TAS. Frequency: Occasional (HP:0040283). (ORPHA:544254)
- Cutaneous photosensitivity (HP:0000992): An increased sensitivity of the skin to light. Photosensitivity may result in a rash upon exposure to the sun (which is known as photodermatosis). Photosensitivity can be diagnosed by phototests in which light is shone on small areas of skin. Evidence: TAS. Frequency: Occasional (HP:0040283). (ORPHA:544254)
- Tremor (HP:0001337): An unintentional, oscillating to-and-fro muscle movement about a joint axis. Evidence: TAS. Frequency: Occasional (HP:0040283). (ORPHA:544254)
- Absent speech (HP:0001344): Complete lack of development of speech and language abilities. Evidence: TAS. Frequency: Occasional (HP:0040283). (ORPHA:544254)
- Obsessive-compulsive trait (HP:0008770): The presence of one or more obsessive-compulsive personality traits. Obsessions refer to persistent intrusive thoughts, and compulsions to intrusive behaviors, which the affected person experiences as involuntary, senseless, or repugnant. Evidence: TAS. Frequency: Occasional (HP:0040283). (ORPHA:544254)
- Feeding difficulties in infancy (HP:0008872): Impaired feeding performance of an infant as manifested by difficulties such as weak and ineffective sucking, brief bursts of sucking, and falling asleep during sucking. There may be difficulties with chewing or maintaining attention. Evidence: TAS. Frequency: Occasional (HP:0040283). (ORPHA:544254)
- Myoclonic absence seizure (HP:0011150): Myoclonic absence seizure is a type of generalized non-motor (absence) seizure characterized by an interruption of ongoing activities, a blank stare and rhythmic three-per-second myoclonic movements, causing ratcheting abduction of the upper limbs leading to progressive arm elevation, and associated with 3 Hz generalized spike-wave discharges on the electroencephalogram. Duration is typically 10-60 s. Whilst impairment of consciousness may not be obvious the ILAE classified this seizure as a generalized non-motor seizure in 2017. Evidence: TAS. Frequency: Occasional (HP:0040283). (ORPHA:544254)
- Abnormal subarachnoid space morphology (HP:0012703): Abnormality in the space in the meninges beneath the arachnoid membrane and above the pia mater that contains the cerebrospinal fluid. Evidence: TAS. Frequency: Occasional (HP:0040283). (ORPHA:544254)
- Reduced social responsiveness (HP:0012760): A reduced ability to participate in the back-and-forth flow of social interaction appropriate to culture and developmental level, which is normally characterized by an influence of the behavior of one person on the behavior of another person. This results in difficulty interacting with others through emotional, physical, or verbal communication. Evidence: TAS. Frequency: Occasional (HP:0040283). (ORPHA:544254)
- Abnormal tongue physiology (HP:0030810): Any functional anomaly of the tongue. Evidence: TAS. Frequency: Occasional (HP:0040283). (ORPHA:544254)
- Anteverted ears (HP:0040080). Evidence: TAS. Frequency: Occasional (HP:0040283). (ORPHA:544254)
- Recurrent hand flapping (HP:0100023): A type of repetitive behavior in which the affected individual repeatedly waves the hands and/or arms rhythmically. Evidence: TAS. Frequency: Occasional (HP:0040283). (ORPHA:544254)
- Postaxial polydactyly (HP:0100259): A form of polydactyly in which the extra digit or digits are localized on the side of the fifth finger or fifth toe. Evidence: TAS. Frequency: Occasional (HP:0040283). (ORPHA:544254)
These phenotypes are associated with the disease SYNGAP1-related developmental and epileptic encephalopathy (ORPHA:544254).