- 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: IEA. (OMIM:261630)
- Progressive neurologic deterioration (HP:0002344). Evidence: IEA. (OMIM:261630)
- Microcephaly (HP:0000252): Head circumference below 2 standard deviations below the mean for age and gender. Evidence: IEA. (OMIM:261630)
- Dysphagia (HP:0002015): Difficulty in swallowing. Evidence: IEA. (OMIM:261630)
- Choreoathetosis (HP:0001266): Involuntary movements characterized by both athetosis (inability to sustain muscles in a fixed position) and chorea (widespread jerky arrhythmic movements). Evidence: IEA. (OMIM:261630)
- 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: IEA. (OMIM:261630)
- 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: IEA. (OMIM:261630)
- Excessive salivation (HP:0003781): Excessive production of saliva. Evidence: TAS. (OMIM:261630)
- 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: IEA. (OMIM:261630)
- 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: IEA. Frequency: 20/20. (OMIM:261630)
- Infantile onset (HP:0003593): Onset of signs or symptoms of disease between 28 days to one year of life. Evidence: IEA. (OMIM:261630)
- Diminished tissue dihydropteridine reductase activity (HP:6000966): Concentration or activity of dihydropteridine reductase (EC 1.6.99.7) below the lower limit of normal. This enzyme can be measured in multiple tissues including leukocytes and erythrocytes. Evidence: PCS. Frequency: 2/2. (PMID:7110817)
- 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:261630)
- Variable expressivity (HP:0003828): A variable severity of phenotypic features. Evidence: IEA. (OMIM:261630)
- 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: IEA. (OMIM:261630)
- Recurrent fever (HP:0001954): Periodic (episodic or recurrent) bouts of fever. Evidence: IEA. (OMIM:261630)
- Hyperphenylalaninemia (HP:0004923): The concentration of L-phenylalanine in the blood circulation is above the upper limit of normal. Evidence: IEA. (OMIM:261630)
- Cerebral calcification (HP:0002514): The presence of calcium deposition within the cerebrum. Evidence: IEA. (OMIM:261630)
- 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:261630)
- Tremor (HP:0001337): An unintentional, oscillating to-and-fro muscle movement about a joint axis. Evidence: IEA. (OMIM:261630)
- Myoclonus (HP:0001336): Very brief, involuntary random muscular contractions occurring at rest, in response to sensory stimuli, or accompanying voluntary movements. Evidence: IEA. (OMIM:261630)
These phenotypes are associated with the disease dihydropteridine reductase deficiency (OMIM:261630).