- Clonus (HP:0002169): A series of rhythmic and involuntary muscle contractions (at a frequency of about 5 to 7 Hz) that occur in response to an abruptly applied and sustained stretch. Evidence: PCS. Frequency: 1/1. (PMID:29517768)
- Scoliosis (HP:0002650): The presence of an abnormal lateral curvature of the spine. Evidence: PCS. Frequency: 1/1. (PMID:29517768)
- Distal amyotrophy (HP:0003693): Muscular atrophy affecting muscles in the distal portions of the extremities. Evidence: PCS. Frequency: 1/1. (PMID:29517768)
- Areflexia (HP:0001284): Absence of neurologic reflexes such as the knee-jerk reaction. Evidence: PCS. Frequency: 1/1. (PMID:29517768)
- Distal muscle weakness (HP:0002460): Reduced strength of the musculature of the distal extremities. Evidence: PCS. Frequency: 1/1. Onset: Childhood onset (HP:0011463). (PMID:29517768)
- Elevated urinary quinolinic acid level (HP:6000335): The amount of quinolinic acid in the urine, normalized for urine concentration, is above the upper limit of normal. Quinolinic acids is a pyridinedicarboxylic acid that is pyridine substituted by carboxy groups at positions 2 and 3. It is a metabolite of tryptophan. Evidence: PCS. Frequency: 1/1. (PMID:29517768)
- Weakness of facial musculature (HP:0030319): Reduced strength of one or more muscles innervated by the facial nerve (the seventh cranial nerve). Evidence: PCS. Frequency: 1/1. (PMID:29517768)
- Hand muscle atrophy (HP:0009130): Muscular atrophy involving the muscles of the hand. Evidence: PCS. Frequency: 1/1. (PMID:29517768)
- Failure to thrive (HP:0001508): Failure to thrive (FTT) refers to a child whose physical growth is substantially below the norm. Evidence: PCS. Frequency: 1/1. (PMID:29517768)
- Reduced forced vital capacity (HP:0032341): An abnormal reduction in the amount of air a person can expel following maximal inspiration. Evidence: PCS. Frequency: 1/1. (PMID:29517768)
- Axonal degeneration (HP:0040078). Evidence: PCS. Frequency: 1/1. (PMID:29517768)
- Foot dorsiflexor weakness (HP:0009027): Weakness of the muscles responsible for dorsiflexion of the foot, that is, of the movement of the toes towards the shin. The foot dorsiflexors include the tibialis anterior, the extensor hallucis longus, the extensor digitorum longus, and the peroneus tertius muscles. Evidence: PCS. Frequency: 1/1. (PMID:29517768)
- 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:29517768)
- Lacticaciduria (HP:0003648): An increased concentration of lactic acid in the urine. Evidence: PCS. Frequency: 1/1. (PMID:29517768)
- Microcytic anemia (HP:0001935): A kind of anemia in which the volume of the red blood cells is reduced. Evidence: PCS. Frequency: 1/1. (PMID:29517768)
- Tongue fasciculations (HP:0001308): Fasciculations or fibrillation affecting the tongue muscle. Evidence: PCS. Frequency: 1/1. (PMID:29517768)
- Falls (HP:0002527). Evidence: PCS. Frequency: 1/1. Onset: Childhood onset (HP:0011463). (PMID:29517768)
- Proximal muscle weakness (HP:0003701): A lack of strength of the proximal muscles. Evidence: PCS. Frequency: 1/1. Onset: Juvenile onset (HP:0003621). (PMID:29517768)
These phenotypes are associated with the disease mitochondrial DNA depletion syndrome 18 (OMIM:618811).