- Spastic tetraplegia (HP:0002510, a Human Phenotype Ontology term): Spastic paralysis affecting all four limbs. Evidence: PCS. Frequency: 7/7. (PMID:19465911)
- Developmental regression (HP:0002376, a Human Phenotype Ontology term): Loss of developmental skills, as manifested by loss of developmental milestones. Evidence: PCS. Frequency: 7/7. (PMID:19465911)
- Irritability (HP:0000737, a Human Phenotype Ontology term): An emotional state characterized by negative feelings of heightened frustration, annoyance, or feeling upset, often triggered by internal factors (e.g., fatigue, hunger, unfulfilled desires) or external factors (e.g., social or environmental challenges). Irritability may be unpredictable, and is accompanied by a lowered threshold for emotional reactivity and observable features (speech, facial expressions, or psychomotor activity). Evidence: PCS. Frequency: 3/7. (PMID:19465911)
- Leukoencephalopathy (HP:0002352, a Human Phenotype Ontology term): This term describes abnormality of the white matter of the cerebrum resulting from damage to the myelin sheaths of nerve cells. Evidence: PCS. Frequency: 6/6. (PMID:19465911)
- Infantile onset (HP:0003593, a Human Phenotype Ontology term): Onset of signs or symptoms of disease between 28 days to one year of life. Evidence: PCS. Frequency: 7/7. (PMID:19465911)
- Reduced brain N-acetyl aspartate level by MRS (HP:0012708, a Human Phenotype Ontology term): A decrease in the level of N-acetyl aspartate in the brain identified by magnetic resonance spectroscopy (MRS). Evidence: PCS. (PMID:19465911)
- Autosomal recessive inheritance (HP:0000007, a Human Phenotype Ontology term): 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:19465911)
- Growth delay (HP:0001510, a Human Phenotype Ontology term): A deficiency or slowing down of growth pre- and postnatally. Evidence: PCS. Frequency: 6/7. (PMID:19465911)
These phenotypes are associated with the disease mitochondrial complex 2 deficiency, nuclear type 2 (OMIM:619166, an entry in Online Mendelian Inheritance in Man).