- Hypertonia (HP:0001276): A condition in which there is increased muscle tone so that arms or legs, for example, are stiff and difficult to move. Evidence: PCS. Frequency: 1/1. (PMID:37468577)
- Poor head control (HP:0002421): Difficulty to maintain correct position of the head while standing or sitting. Infant head lag is observed when the head seems to flop around or lags posteriorly behind the trunk. Several articles have maintained that head lag should be absent by age 3 to 4 months. Evidence: PCS. Frequency: 1/1. (PMID:37468577)
- Dysphagia (HP:0002015): Difficulty in swallowing. Evidence: PCS. Frequency: 1/1. (PMID:37468577)
- Abnormal reflex (HP:0031826): Any anomaly of a reflex, i.e., of an automatic response mediated by the nervous system (a reflex does not need the intervention of conscious thought to occur). Evidence: PCS. Frequency: 0/1. (PMID:37468577)
- Increased circulating pyruvate concentration (HP:0003542): The concentration of pyruvate in the blood circulation is above the upper limit of normal. Evidence: PCS. Frequency: 1/1. (PMID:37468577)
- Poor suck (HP:0002033): An inadequate sucking reflex, resulting in the difficult of newborns to be breast-fed. Evidence: PCS. Frequency: 1/1. (PMID:37468577)
- Polyneuropathy (HP:0001271): A generalized disorder of peripheral nerves. Evidence: PCS. Frequency: 1/1. (PMID:37468577)
- 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: 1/1. (PMID:37468577)
- 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: 1/1. (PMID:37468577)
- Generalized hypotonia (HP:0001290): Generalized muscular hypotonia (abnormally low muscle tone). Evidence: PCS. Frequency: 1/1. (PMID:37468577)
- 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:37468577)
- Elevated urine fumaric acid level (HP:0034648): The concentration of fumaric acid in the urine, normalized for urine concentration, is above the upper limit of normal. Evidence: PCS. Frequency: 1/1. (PMID:37468577)
- Third trimester onset (HP:0034197): This term refers to a phenotypic feature that was first observed prior to birth during the third trimester, which is defined as 28 weeks and zero days (28+0) of gestation and beyond. Evidence: PCS. Frequency: 1/1. (PMID:37468577)
- Wolff-Parkinson-White syndrome (HP:0001716): A disorder of the cardiac conduction system of the heart characterized by ventricular preexcitation due to the presence of an abnormal accessory atrioventricular electrical conduction pathway. Evidence: PCS. Frequency: 1/1. (PMID:37468577)
- Hypertrophic cardiomyopathy (HP:0001639): Hypertrophic cardiomyopathy (HCM) is defined by the presence of increased ventricular wall thickness or mass in the absence of loading conditions (hypertension, valve disease) sufficient to cause the observed abnormality. Evidence: PCS. Frequency: 1/1. (PMID:37468577)
- Nasogastric tube feeding (HP:0040288): The condition of inability to eat normally treated by placement of a thin tube through the nose into the stomach that is then used to carry food. Evidence: PCS. Frequency: 1/1. (PMID:37468577)
- Decreased amplitude of sensory action potentials (HP:0007078): A reduction in the amplitude of sensory nerve action potential. This feature is measured by nerve conduction studies. Evidence: PCS. Frequency: 1/1. (PMID:37468577)
- Left ventricular hypertrophy (HP:0001712): Enlargement or increased size of the heart left ventricle. Evidence: PCS. Frequency: 1/1. (PMID:37468577)
- 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:37468577)
- Decreased activity of mitochondrial complex IV (HP:0008347): A reduction in the activity of the mitochondrial respiratory chain complex IV, which is part of the electron transport chain in mitochondria. Evidence: PCS. Frequency: 1/1. (PMID:37468577)
- Postnatal growth retardation (HP:0008897): Slow or limited growth after birth. Evidence: PCS. Frequency: 1/1. (PMID:37468577)
- Delayed ability to sit (HP:0025336): A failure to achieve the ability to sit at an appropriate developmental stage. Most children sit with support at 6 months of age and sit steadily without support at 9 months of age. Evidence: PCS. Frequency: 1/1. (PMID:37468577)
- Cytochrome C oxidase-negative muscle fibers (HP:0003688): An abnormally reduced activity of the enzyme cytochrome C oxidase in muscle tissue. Evidence: PCS. Frequency: 1/1. (PMID:37468577)
- Hyperalaninemia (HP:0003348): An increased concentration of alanine in the blood. Evidence: PCS. Frequency: 1/1. (PMID:37468577)
These phenotypes are associated with the disease mitochondrial complex 4 deficiency, nuclear type 25 (OMIM:621487).