- Progressive microcephaly (HP:0000253): Progressive microcephaly is diagnosed when the head circumference falls progressively behind age- and gender-dependent norms. Evidence: PCS. Frequency: 4/4. (PMID:31422819)
- Cerebellar vermis hypoplasia (HP:0001320): Underdevelopment of the vermis of cerebellum. Evidence: PCS. Frequency: 3/4. (PMID:31422819)
- Decreased body weight (HP:0004325): Abnormally low body weight. Evidence: PCS. Frequency: 3/4. (PMID:31422819)
- Cerebral atrophy (HP:0002059): Atrophy (wasting, decrease in size of cells or tissue) affecting the cerebrum. Evidence: PCS. Frequency: 3/4. (PMID:31422819)
- Spastic tetraplegia (HP:0002510): Spastic paralysis affecting all four limbs. Evidence: PCS. Frequency: 2/4. (PMID:31422819)
- Absent speech (HP:0001344): Complete lack of development of speech and language abilities. Evidence: PCS. Frequency: 3/4. (PMID:31422819)
- 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: PCS. Frequency: 4/4. (PMID:31422819)
- Inability to walk (HP:0002540): Incapability to ambulate. Evidence: PCS. Frequency: 3/4. (PMID:31422819)
- Hypoplasia of the corpus callosum (HP:0002079): Underdevelopment of the corpus callosum. Evidence: PCS. Frequency: 3/4. (PMID:31422819)
- Short stature (HP:0004322): A height below that which is expected according to age and gender norms. Although there is no universally accepted definition of short stature, many refer to "short stature" as height more than 2 standard deviations below the mean for age and gender (or below the 3rd percentile for age and gender dependent norms). Evidence: PCS. Frequency: 3/4. (PMID:31422819)
- 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: 4/4. Onset: Infantile onset (HP:0003593). (PMID:31422819)
- Increased circulating lactate concentration (HP:0002151): Abnormally increased level of blood lactate (2-hydroxypropanoic acid). Lactate is produced from pyruvate by lactate dehydrogenase during normal metabolism. The terms lactate and lactic acid are often used interchangeably but lactate (the component measured in blood) is strictly a weak base whereas lactic acid is the corresponding acid. Lactic acidosis is often used clinically to describe elevated lactate but should be reserved for cases where there is a corresponding acidosis (pH below 7.35). Evidence: PCS. Frequency: 4/4. (PMID:31422819)
- 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: PCS. Frequency: 4/4. (PMID:31422819)
- Recurrent infections (HP:0002719): Increased susceptibility to infections as manifested by repeated bouts of infection. Evidence: PCS. Frequency: 4/4. (PMID:31422819)
- 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:31422819)
- 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: 4/4. (PMID:31422819)
- Hyperammonemia (HP:0001987): An increased concentration of ammonia in the blood. Evidence: PCS. Frequency: 4/4. (PMID:31422819)
- Neonatal hypotonia (HP:0001319): Muscular hypotonia (abnormally low muscle tone) manifesting in the neonatal period. Evidence: PCS. Frequency: 4/4. (PMID:31422819)
- Spastic paraparesis (HP:0002313): Partial loss of the ability to move the lower limbs accompanied by spasticity of the lower limbs. Evidence: PCS. Frequency: 2/4. (PMID:31422819)
These phenotypes are associated with the disease developmental and epileptic encephalopathy, 82 (OMIM:618721).