- Hypsarrhythmia (HP:0002521): Hypsarrhythmia is abnormal interictal high amplitude waves and a background of irregular spikes. There is continuous (during wakefulness), high-amplitude (>200 Hz), generalized polymorphic slowing with no organized background and multifocal spikes demonstrated by electroencephalography (EEG). Evidence: PCS. Frequency: 3/3. Onset: Infantile onset (HP:0003593). (PMID:29410512)
- Sloping forehead (HP:0000340): Inclination of the anterior surface of the forehead from the vertical more than two standard deviations above the mean (objective); or apparently excessive posterior sloping of the forehead in a lateral view. Evidence: PCS. (PMID:29410512)
- Upslanted palpebral fissure (HP:0000582): The palpebral fissure inclination is more than two standard deviations above the mean for age (objective); or, the inclination of the palpebral fissure is greater than typical for age. Evidence: PCS. (PMID:29410512)
- Decreased liver function (HP:0001410): Reduced ability of the liver to perform its functions. Evidence: IEA. Frequency: Very rare (HP:0040284). (OMIM:618437)
- Anteverted nares (HP:0000463): Anteriorly-facing nostrils viewed with the head in the Frankfurt horizontal and the eyes of the observer level with the eyes of the subject. This gives the appearance of an upturned nose (upturned nasal tip). Evidence: PCS. (PMID:29410512)
- 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: 3/3. (PMID:29410512)
- Cerebral cortical atrophy (HP:0002120): Atrophy of the cortex of the cerebrum. Evidence: PCS. (PMID:29410512)
- 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: PCS. (PMID:29410512)
- Cerebral visual impairment (HP:0100704): A form of loss of vision caused by damage to the visual cortex rather than a defect in the eye. Evidence: IEA. (OMIM:618437)
- Hypertelorism (HP:0000316): Interpupillary distance more than 2 SD above the mean (alternatively, the appearance of an increased interpupillary distance or widely spaced eyes). Evidence: PCS. (PMID:29410512)
- 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: PCS. Frequency: 3/3. (PMID:29410512)
- CNS hypomyelination (HP:0003429): Reduced amount of myelin in the central nervous system resulting from defective myelinogenesis. Evidence: PCS. (PMID:29410512)
- Prolonged neonatal jaundice (HP:0006579): Neonatal jaundice refers to a yellowing of the skin and other tissues of a newborn infant as a result of increased concentrations of bilirubin in the blood. Neonatal jaundice affects over half of all newborns to some extent in the first week of life. Prolonged neonatal jaundice is said to be present if the jaundice persists for longer than 14 days in term infants and 21 days in preterm infants. Evidence: PCS. Frequency: 2/3. Onset: Neonatal onset (HP:0003623). (PMID:29410512)
- Hyperreflexia (HP:0001347): Hyperreflexia is the presence of hyperactive stretch reflexes of the muscles. Evidence: IEA. (OMIM:618437)
- Axial hypotonia (HP:0008936): Muscular hypotonia (abnormally low muscle tone) affecting the musculature of the trunk. Evidence: IEA. (OMIM:618437)
- Absent speech (HP:0001344): Complete lack of development of speech and language abilities. Evidence: PCS. Frequency: 3/3. (PMID:29410512)
- Wide nasal bridge (HP:0000431): Increased breadth of the nasal bridge (and with it, the nasal root). Evidence: PCS. (PMID:29410512)
- Frontal cortical atrophy (HP:0006913): Atrophy of the frontal cortex. Evidence: PCS. (PMID:29410512)
- Babinski sign (HP:0003487): Upturning of the big toe (and sometimes fanning of the other toes) in response to stimulation of the sole of the foot. If the Babinski sign is present it can indicate damage to the corticospinal tract. Evidence: PCS. (PMID:29410512)
- Short chin (HP:0000331): Decreased vertical distance from the vermilion border of the lower lip to the inferior-most point of the chin. Evidence: PCS. (PMID:29410512)
- Hypoplasia of the corpus callosum (HP:0002079): Underdevelopment of the corpus callosum. Evidence: PCS. (PMID:29410512)
- Open mouth (HP:0000194): A facial appearance characterized by a permanently or nearly permanently opened mouth. Evidence: PCS. (PMID:29410512)
- 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: PCS. Frequency: 3/3. (PMID:29410512)
- Secondary microcephaly (HP:0005484): Head circumference which falls below 2 standard deviations below the mean for age and gender because of insufficient head growth after birth. Evidence: PCS. Frequency: 3/3. (PMID:29410512)
- 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: IEA. (OMIM:618437)
- 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:29410512)
- Cardiomyopathy (HP:0001638): A myocardial disorder in which the heart muscle is structurally and functionally abnormal, in the absence of coronary artery disease, hypertension, valvular disease and congenital heart disease sufficient to cause the observed myocardial abnormality. Evidence: IEA. Frequency: Very rare (HP:0040284). (OMIM:618437)
- Optic atrophy (HP:0000648): Atrophy of the optic nerve. Optic atrophy results from the death of the retinal ganglion cell axons that comprise the optic nerve and manifesting as a pale optic nerve on fundoscopy. Evidence: IEA. (OMIM:618437)
- 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:618437)
- Optic disc pallor (HP:0000543): A pale yellow discoloration of the optic disc (the area of the optic nerve head in the retina). The optic disc normally has a pinkish hue with a central yellowish depression. Evidence: PCS. (PMID:29410512)
- Proptosis (HP:0000520): An eye that is protruding anterior to the plane of the face to a greater extent than is typical. Evidence: PCS. (PMID:29410512)
- Short philtrum (HP:0000322): Distance between nasal base and midline upper lip vermilion border more than 2 SD below the mean. Alternatively, an apparently decreased distance between nasal base and midline upper lip vermilion border. Evidence: PCS. (PMID:29410512)
- Spasticity (HP:0001257): A motor disorder characterized by a velocity-dependent increase in tonic stretch reflexes with increased muscle tone, exaggerated (hyperexcitable) tendon reflexes. Evidence: IEA. (OMIM:618437)
These phenotypes are associated with the disease developmental and epileptic encephalopathy, 75 (OMIM:618437).