- 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:615476)
- Hyporeflexia (HP:0001265): Reduction of neurologic reflexes such as the knee-jerk reaction. Evidence: TAS. (OMIM:615476)
- Oligohydramnios (HP:0001562): Diminished amniotic fluid volume in pregnancy. Evidence: PCS. Frequency: 1/3. (PMID:23932106)
- Downslanted palpebral fissures (HP:0000494): The palpebral fissure inclination is more than two standard deviations below the mean. Evidence: TAS. (OMIM:615476)
- Polyhydramnios (HP:0001561): The presence of excess amniotic fluid in the uterus during pregnancy. Evidence: PCS. Frequency: 1/3. (PMID:23932106)
- 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: TAS. (OMIM:615476)
- Absent speech (HP:0001344): Complete lack of development of speech and language abilities. Evidence: PCS. Frequency: 2/3. (PMID:23932106)
- 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. (OMIM:615476)
- Generalized non-motor (absence) seizure (HP:0002121): A generalized non-motor (absence) seizure is a type of a type of dialeptic seizure that is of electrographically generalized onset. It is a generalized seizure characterized by an interruption of activities, a blank stare, and usually the person will be unresponsive when spoken to. Any ictal motor phenomena are minor in comparison to these non-motor features. Evidence: TAS. (OMIM:615476)
- 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. (OMIM:615476)
- 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: PCS. Frequency: 2/2. Onset: Infantile onset (HP:0003593). (PMID:23932106)
- Infantile onset (HP:0003593): Onset of signs or symptoms of disease between 28 days to one year of life. Evidence: PCS. Frequency: 3/3. (PMID:23932106)
- Profound global developmental delay (HP:0012736): A profound delay in the achievement of motor or mental milestones in the domains of development of a child. Evidence: PCS. Frequency: 3/3. (PMID:23932106)
- Atypical absence seizure (HP:0007270): An atypical absence seizure is a type of generalized non-motor (absence) seizure characterized by interruption of ongoing activities and reduced responsiveness. In comparison to a typical absence seizure, changes in tone may be more pronounced, onset and/or cessation may be less abrupt, and the duration of the ictus and post-ictal recovery may be longer. Although not always available, an EEG often demonstrates slow (<3 Hz), irregular, generalized spike-wave activity. Evidence: PCS. Frequency: 1/3. (PMID:23932106)
- Thick corpus callosum (HP:0007074): Increased vertical dimension of the corpus callosum. This feature can be visualized by sagittal sections on magnetic resonance tomography imaging of the brain. Evidence: TAS. (OMIM:615476)
- Tonic seizure (HP:0032792): A tonic seizure is a type of motor seizure characterized by unilateral or bilateral limb stiffening or elevation, often with neck stiffening. Evidence: PCS. Frequency: 1/3. (PMID:23932106)
- Ptosis (HP:0000508): The upper eyelid margin is positioned 3 mm or more lower than usual and covers the superior portion of the iris (objective); or, the upper lid margin obscures at least part of the pupil (subjective). Evidence: TAS. (OMIM:615476)
- Autosomal recessive inheritance (HP:0000007): A mode of inheritance that is observed for traits related to a gene encoded on one of the autosomes (i.e., the human chromosomes 1-22) in which a trait manifests in individuals with two pathogenic alleles, either homozygotes (two copies of the same mutant allele) or compound heterozygotes (whereby each copy of a gene has a distinct mutant allele). Evidence: PCS. (PMID:23932106)
- High forehead (HP:0000348): An abnormally increased height of the forehead. Evidence: TAS. (OMIM:615476)
- Epileptic encephalopathy (HP:0200134): A condition in which epileptiform abnormalities are believed to contribute to the progressive disturbance in cerebral function. Epileptic encephalaopathy is characterized by (1) electrographic EEG paroxysmal activity that is often aggressive, (2) seizures that are usually multiform and intractable, (3) cognitive, behavioral and neurological deficits that may be relentless, and (4) sometimes early death. Evidence: IEA. (OMIM:615476)
- Bilateral tonic-clonic seizure with focal onset (HP:0007334): A bilateral tonic-clonic seizure with focal onset is a focal-onset seizure which progresses into a bilateral tonic-clonic phase. Evidence: PCS. Frequency: 1/3. (PMID:23932106)
- Aortic regurgitation (HP:0001659): An insufficiency of the aortic valve, leading to regurgitation (backward flow) of blood from the aorta into the left ventricle. Evidence: PCS. Frequency: 1/3. (PMID:23932106)
- Focal-onset seizure (HP:0007359): A focal-onset seizure is a type of seizure originating within networks limited to one hemisphere. They may be discretely localized or more widely distributed, and may originate in subcortical structures. Evidence: TAS. (OMIM:615476)
- Atrial septal defect (HP:0001631): Atrial septal defect (ASD) is a congenital abnormality of the interatrial septum that enables blood flow between the left and right atria via the interatrial septum. Evidence: PCS. Frequency: 1/3. (PMID:23932106)
These phenotypes are associated with the disease developmental and epileptic encephalopathy, 18 (OMIM:615476).