- 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: IEA. (OMIM:608049)
- EEG abnormality (HP:0002353): Abnormality observed by electroencephalogram (EEG), which is used to record of the brain's spontaneous electrical activity from multiple electrodes placed on the scalp. Evidence: IEA. Frequency: Frequent (HP:0040282). (OMIM:608049)
- 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: IEA. Frequency: Frequent (HP:0040282). (OMIM:608049)
- Increased serum serotonin (HP:0003144): A increased concentration of serotonin in the blood. Evidence: IEA. Frequency: Frequent (HP:0040282). (OMIM:608049)
- Ketonuria (HP:0002919): High levels of ketone bodies (acetoacetic acid, beta-hydroxybutyric acid, and acetone) in the urine. Ketone bodies are insignificant in the blood and urine of normal individuals in the postprandial or overnight-fasted state. Evidence: IEA. (OMIM:608049)
- Childhood onset (HP:0011463): Onset of disease at the age of between 1 and 5 years. Evidence: IEA. (OMIM:608049)
- Autism (HP:0000717): Autism is a neurodevelopmental disorder characterized by impaired social interaction and communication, and by restricted and repetitive behavior. Autism begins in childhood. It is marked by the presence of markedly abnormal or impaired development in social interaction and communication and a markedly restricted repertoire of activity and interest. Manifestations of the disorder vary greatly depending on the developmental level and chronological age of the individual (DSM-IV). Evidence: TAS. (OMIM:608049)
- Reduced ability to form peer relationships (HP:0000728): Difficulty to establish relations with others in a comparable social group (peers) that may be manifested in pehnomena such as not being able to initiative a conversation, understand social cues, or to discuss shared interests. This feature is associated with poor integration within a community or group. Evidence: IEA. (OMIM:608049)
- Restrictive behavior (HP:0000723): Behavior characterized by an abnormal limitation to a few interests and activities. Evidence: TAS. (OMIM:608049)
- Non-Mendelian inheritance (HP:0001426): A mode of inheritance that depends on genetic determinants in more than one gene. Evidence: IEA. (OMIM:608049)
- Motor stereotypy (HP:0000733): Use of the same abnormal action in response to certain triggers or at random. They may be used as a way to regulate one's internal state but must otherwise have no apparent functional purpose. Evidence: TAS. (OMIM:608049)
- Abnormal nonverbal communicative behavior (HP:0000758): Abnormalities in eye contact, communicative facial expressions, gesture use, or the use of others' bodies to communicate convey shared meanings within a culture that replace or supplement verbal communication. Evidence: TAS. (OMIM:608049)
- Sporadic (HP:0003745): Cases of the disease in question occur without a previous family history, i.e., as isolated cases without being transmitted from a parent and without other siblings being affected. Evidence: IEA. (OMIM:608049)
- Inflexible adherence to routines (HP:0000732): A need to strictly adhere to repetitive routines or patterns of behavior which are created by the environment. One becomes upset or distressed when their routines are disrupted or altered. Evidence: IEA. (OMIM:608049)
- 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: IEA. (OMIM:608049)
- Lack of spontaneous play (HP:0000721). Evidence: IEA. (OMIM:608049)
These phenotypes are associated with the disease autism, susceptibility to, 3 (OMIM:608049).