- Hyperkinetic movements (HP:0002487): Motor hyperactivity with excessive movement of muscles of the body as a whole. Evidence: TAS. (OMIM:233910)
- Lethargy (HP:0001254): A state of fatigue, either physical or mental slowness and sluggishness, with difficulties in initiating or performing simple tasks. Distinguished from apathy which implies indifference and a lack of desire or interest in the task. A person with lethargy may have the desire, but not the energy to engage in personal or socially relevant tasks. Evidence: IEA. (OMIM:233910)
- Progressive neurologic deterioration (HP:0002344). Evidence: IEA. (OMIM:233910)
- Dystonia (HP:0001332): An abnormally increased muscular tone that causes fixed abnormal postures. There is a slow, intermittent twisting motion that leads to exaggerated turning and posture of the extremities and trunk. Evidence: PCS. Frequency: 1/1. (PMID:7869202)
- Seizure (HP:0001250): A seizure is an intermittent abnormality of nervous system physiology characterized by a transient occurrence of signs and/or symptoms due to abnormal excessive or synchronous neuronal activity in the brain. Evidence: PCS. Frequency: 1/1. (PMID:7730309)
- 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: 1/1. (PMID:7730309)
- 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: IEA. (OMIM:233910)
- Severe muscular hypotonia (HP:0006829): A severe degree of muscular hypotonia characterized by markedly reduced muscle tone. Evidence: IEA. (OMIM:233910)
- Infantile onset (HP:0003593): Onset of signs or symptoms of disease between 28 days to one year of life. Evidence: PCS. Frequency: 1/1. (PMID:7869202)
- Generalized hypotonia (HP:0001290): Generalized muscular hypotonia (abnormally low muscle tone). Evidence: PCS. Frequency: 1/1. (PMID:7869202)
- Irritability (HP:0000737): 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: IEA. (OMIM:233910)
- Decreased urinary biopterin level (HP:0040417): The amount of biopterin in the urine, normalized for urine concentration, is below the lower limit of normal. Evidence: PCS. Frequency: 1/1. (PMID:7730309)
- Increased CSF phenylalanine concentration (HP:0500223): Abnormally increased levels of phenylalanine in cerebrospinal fluid. Evidence: PCS. Frequency: 1/1. (PMID:7869202)
- Intellectual disability (HP:0001249): The term intellectual disability or intellectual developmental disorder is used to describe significantly sub-average intellectual and adaptive functioning based on clinical assessment and as measured by individually administered, appropriately normed, standardized and validated tests of intellectual functioning and adaptive behavior, with onset during the developmental period from infancy through adolescence. Evidence: IEA. (OMIM:233910)
- Neonatal onset (HP:0003623): Onset of signs or symptoms of disease within the first 28 days of life. Evidence: PCS. Frequency: 1/1. (PMID:7730309)
- Elevated urinary sulfatide level (HP:6000120): The amount of sulfatides in the urine, normalized for urine concentration, is above the upper limit of normal. Sulfatides are derived from GalCer via esterification of a sulfate group to 3-hydroxyl of the galactose moiety. Evidence: TAS. (OMIM:233910)
- Dysphagia (HP:0002015): Difficulty in swallowing. Evidence: IEA. (OMIM:233910)
- Abnormality of eye movement (HP:0000496): An abnormality in voluntary or involuntary eye movements or their control. Evidence: IEA. (OMIM:233910)
- Choreoathetosis (HP:0001266): Involuntary movements characterized by both athetosis (inability to sustain muscles in a fixed position) and chorea (widespread jerky arrhythmic movements). Evidence: PCS. Frequency: 1/1. (PMID:7730309)
- Excessive salivation (HP:0003781): Excessive production of saliva. Evidence: TAS. (OMIM:233910)
- 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:7730309)
- Poor suck (HP:0002033): An inadequate sucking reflex, resulting in the difficult of newborns to be breast-fed. Evidence: PCS. Frequency: 1/1. (PMID:7730309)
- 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: 2/2. (PMID:7869202;PMID:7730309)
- Decreased urinary neopterin level (HP:0040420): The amount of neopterin in the urine, normalized for urine concentration, is below the lower limit of normal. Evidence: PCS. Frequency: 1/1. (PMID:7730309)
- Limb hypertonia (HP:0002509). Evidence: IEA. (OMIM:233910)
- 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:7869202)
- Recurrent fever (HP:0001954): Periodic (episodic or recurrent) bouts of fever. Evidence: IEA. (OMIM:233910)
- Hyperphenylalaninemia (HP:0004923): The concentration of L-phenylalanine in the blood circulation is above the upper limit of normal. Evidence: PCS. Frequency: 2/2. (PMID:7869202;PMID:7730309)
- Tremor (HP:0001337): An unintentional, oscillating to-and-fro muscle movement about a joint axis. Evidence: PCS. Frequency: 1/1. (PMID:7869202)
These phenotypes are associated with the disease GTP cyclohydrolase I deficiency with hyperphenylalaninemia (OMIM:233910).