- 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:22040219)
- Axial hypotonia (HP:0008936): Muscular hypotonia (abnormally low muscle tone) affecting the musculature of the trunk. Evidence: PCS. Frequency: 1/1. (PMID:22040219)
- 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: 4/4. (PMID:11095995;PMID:22040219)
- Bilateral tonic-clonic seizure (HP:0002069): A bilateral tonic-clonic seizure is a seizure defined by a tonic (bilateral increased tone, lasting seconds to minutes) and then a clonic (bilateral sustained rhythmic jerking) phase. Evidence: PCS. Frequency: 3/3. (PMID:11095995)
- Sulfite oxidase deficiency (HP:0003643): Abnormally reduced sulfite oxidase level. Evidence: PCS. Frequency: 1/1. (PMID:22040219)
- Generalized myoclonic seizure (HP:0002123): A generalized myoclonic seizure is a type of generalized motor seizure characterized by bilateral, sudden, brief (<100 ms) involuntary single or multiple contraction of muscles or muscle groups of variable topography (axial, proximal limb, distal). Myoclonus is less regularly repetitive and less sustained than is clonus. Evidence: PCS. Frequency: 1/1. (PMID:22040219)
- Cerebellar hypoplasia (HP:0001321): Cerebellar hypoplasia is a descriptive term implying a cerebellum with a reduced volume, but a normal shape and is stable over time. Evidence: PCS. Frequency: 1/1. (PMID:22040219)
- Generalized-onset seizure (HP:0002197): A generalized-onset seizure is a type of seizure originating at some point within, and rapidly engaging, bilaterally distributed networks. The networks may include cortical and subcortical structures but not necessarily the entire cortex. Evidence: PCS. Frequency: 1/1. (PMID:22040219)
- 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: 1/1. (PMID:22040219)
- Increased urinary taurine (HP:0003166): Increased concentration of taurine in the urine. Evidence: PCS. Frequency: 1/1. (PMID:22040219)
- Molybdenum cofactor deficiency (HP:0003570): Absence of molybdenum cofactor(2-), a cofactor for enzymes including sulfite oxidase, xanthine oxidoreductase, and aldehyde oxidase. Evidence: PCS. Frequency: 1/1. (PMID:11095995)
- Generalized hypotonia (HP:0001290): Generalized muscular hypotonia (abnormally low muscle tone). Evidence: PCS. Frequency: 1/1. (PMID:22040219)
- Severe global developmental delay (HP:0011344): A severe delay in the achievement of motor or mental milestones in the domains of development of a child. Evidence: PCS. Frequency: 3/3. (PMID:11095995)
- Hypoplasia of the pons (HP:0012110): Underdevelopment of the pons. Evidence: PCS. Frequency: 1/1. (PMID:22040219)
- Hypocystinemia (HP:0500152): A decreased amount of cystine in the blood. Evidence: PCS. Frequency: 1/1. (PMID:22040219)
- Reduced eye contact (HP:0000817): A reduced frequency or duration of eye contact. Evidence: PCS. Frequency: 1/1. (PMID:22040219)
- Limb hypertonia (HP:0002509). Evidence: PCS. Frequency: 1/1. (PMID:22040219)
- Hypertaurinemia (HP:0500181): An increased amount of taurine in the blood. Evidence: PCS. Frequency: 1/1. (PMID:22040219)
- 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:11095995)
- Neonatal death (HP:0003811): Death within the first 28 days of life. Evidence: PCS. Frequency: 3/3. (PMID:11095995)
- Hypouricemia (HP:0003537): The concentration of uric acid in the blood circulation is below the lower limit of normal. Evidence: PCS. Frequency: 1/1. (PMID:22040219)
- Polymicrogyria (HP:0002126): Polymicrogyria is a congenital malformation of the cerebral cortex characterized by abnormal cortical layering (lamination) and an excessive number of small gyri (folds). Evidence: PCS. Frequency: 1/1. (PMID:22040219)
- Neonatal onset (HP:0003623): Onset of signs or symptoms of disease within the first 28 days of life. Evidence: PCS. Frequency: 4/4. (PMID:11095995;PMID:22040219)
- Hyperreflexia (HP:0001347): Hyperreflexia is the presence of hyperactive stretch reflexes of the muscles. Evidence: PCS. Frequency: 3/3. (PMID:11095995)
These phenotypes are associated with the disease sulfite oxidase deficiency due to molybdenum cofactor deficiency type C (OMIM:615501).