- Inguinal hernia (HP:0000023): Protrusion of the contents of the abdominal cavity through the inguinal canal. Evidence: PCS. Frequency: 1/2. (PMID:36030551)
- Hypotonia (HP:0001252): Hypotonia is an abnormally low muscle tone (the amount of tension or resistance to movement in a muscle). Even when relaxed, muscles have a continuous and passive partial contraction which provides some resistance to passive stretching. Hypotonia thus manifests as diminished resistance to passive stretching. Hypotonia is not the same as muscle weakness, although the two conditions can co-exist. Evidence: PCS. Frequency: 1/2. (PMID:36030551)
- Rigidity (HP:0002063): Continuous involuntary sustained muscle contraction. When an affected muscle is passively stretched, the degree of resistance remains constant regardless of the rate at which the muscle is stretched. This feature helps to distinguish rigidity from muscle spasticity. Evidence: PCS. Frequency: 1/2. (PMID:36030551)
- Elevated brain lactate level by MRS (HP:0012707): An increase in the level of lactate in the brain identified by magnetic resonance spectroscopy (MRS). Evidence: PCS. Frequency: 1/2. (PMID:36030551)
- Gastroesophageal reflux (HP:0002020): A condition in which the stomach contents leak backwards from the stomach into the esophagus through the lower esophageal sphincter. Evidence: PCS. Frequency: 1/2. (PMID:36030551)
- Infantile onset (HP:0003593): Onset of signs or symptoms of disease between 28 days to one year of life. Evidence: PCS. Frequency: 1/2. (PMID:36030551)
- Abdominal distention (HP:0003270): Distention of the abdomen. Evidence: PCS. Frequency: 1/2. (PMID:36030551)
- Percussion myotonia (HP:0010548): A localized myotonic contraction in a muscle in reaction to percussion (tapping with the examiner's finger, a rubber percussion hammer, or a similar object). Evidence: PCS. Frequency: 1/2. (PMID:36030551)
- Brain atrophy (HP:0012444): Partial or complete wasting (loss) of brain tissue that was once present. Evidence: PCS. Frequency: 2/2. (PMID:36030551)
- Hypoglycemia (HP:0001943): A decreased concentration of glucose in the blood. Evidence: PCS. Frequency: 1/2. (PMID:36030551)
- Clonic seizure (HP:0020221): A clonic seizure is a type of motor seizure characterized by sustained rhythmic jerking, that is regularly repetitive. Evidence: PCS. Frequency: 1/2. (PMID:36030551)
- Fetal distress (HP:0025116): An intrauterine state characterized by suboptimal values in the fetal heart rate, oxygenation of fetal blood, or other parameters indicative of compromise of the fetus. Signs of fetal distress include repetitive variable decelerations, fetal tachycardia or bradycardia, late decelerations, or low biophysical profile. Evidence: PCS. Frequency: 1/2. (PMID:36030551)
- Death in infancy (HP:0001522): Death within the first 24 months of life. Evidence: PCS. Frequency: 2/2. (PMID:36030551)
- Brisk reflexes (HP:0001348): Tendon reflexes that are noticeably more active than usual (conventionally denoted 3+ on clinical examination). Brisk reflexes may or may not indicate a neurological lesion. They are distinguished from hyperreflexia by the fact that hyerreflexia is characterized by hyperactive repeating (clonic) reflexes, which are considered to be always abnormal. Evidence: PCS. Frequency: 1/2. (PMID:36030551)
- Neonatal onset (HP:0003623): Onset of signs or symptoms of disease within the first 28 days of life. Evidence: PCS. Frequency: 1/2. (PMID:36030551)
- Microcephaly (HP:0000252): Head circumference below 2 standard deviations below the mean for age and gender. Evidence: PCS. Frequency: 1/2. (PMID:36030551)
- Feeding difficulties (HP:0011968): Impaired ability to eat related to problems gathering food and getting ready to suck, chew, or swallow it. Evidence: PCS. Frequency: 1/2. (PMID:36030551)
- Hypoventilation (HP:0002791): A reduction in the amount of air transported into the pulmonary alveoli by breathing, leading to hypercapnia (increase in the partial pressure of carbon dioxide). Evidence: PCS. Frequency: 1/2. (PMID:36030551)
- 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: 2/2. (PMID:36030551)
- Increased CSF lactate (HP:0002490): Increased concentration of lactate in the cerebrospinal fluid. Evidence: PCS. Frequency: 1/2. (PMID:36030551)
- Dyskinesia (HP:0100660): A movement disorder which consists of effects including diminished voluntary movements and the presence of involuntary movements. Evidence: PCS. Frequency: 1/2. (PMID:36030551)
- Knee contracture (HP:0034671): Lack of full passive range of motion (restrictions in flexion, extension, or other movements) of the knee joint resulting from structural changes of non-bony tissues, such as muscles, tendons, ligaments, joint capsules and/or skin. Evidence: PCS. Frequency: 1/2. (PMID:36030551)
- Sensorineural hearing impairment (HP:0000407): A type of hearing impairment in one or both ears related to an abnormal functionality of the cochlear nerve. Evidence: PCS. Frequency: 1/2. (PMID:36030551)
- Umbilical hernia (HP:0001537): Protrusion of abdominal contents through a defect in the abdominal wall musculature around the umbilicus. Skin and subcutaneous tissue overlie the defect. Evidence: PCS. Frequency: 1/2. (PMID:36030551)
- 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:36030551)
- Visual impairment (HP:0000505): Visual impairment (or vision impairment) is vision loss (of a person) to such a degree as to qualify as an additional support need through a significant limitation of visual capability resulting from either disease, trauma, or congenital or degenerative conditions that cannot be corrected by conventional means, such as refractive correction, medication, or surgery. Evidence: PCS. Frequency: 1/2. (PMID:36030551)
- Intrauterine growth retardation (HP:0001511): An abnormal restriction of fetal growth with fetal weight below the tenth percentile for gestational age. Evidence: PCS. Frequency: 1/2. (PMID:36030551)
- Focal-onset seizure (HP:0007359): A focal-onset seizure is a type of seizure originating within networks limited to one hemisphere. They may be discretely localized or more widely distributed, and may originate in subcortical structures. Evidence: PCS. Frequency: 1/2. (PMID:36030551)
- Nemaline bodies (HP:0003798): Nemaline rods are abnormal bodies that can occur in skeletal muscle fibers. The rods can be observed on histological analysis of muscle biopsy tissue or upon electron microscopy, where they appear either as extensions of sarcomeric Z-lines, in random array without obvious attachment to Z-lines (often in areas devoid of sarcomeres) or in large clusters localized at the sarcolemma or intermyofibrillar spaces. Evidence: PCS. Frequency: 1/2. (PMID:36030551)
- Elbow contracture (HP:0034391): A limitation in the passive range of motion of the elbow resulting from loss of elasticity in the periarticular tissues owing to structural changes of non-bony tissues, such as muscles, tendons, ligaments, joint capsules or skin. Evidence: PCS. Frequency: 1/2. (PMID:36030551)
These phenotypes are associated with the disease mitochondrial complex IV deficiency, nuclear type 23 (OMIM:620275).