- Hyperphenylalaninemia (HP:0004923): The concentration of L-phenylalanine in the blood circulation is above the upper limit of normal. Evidence: TAS. Frequency: Very frequent (HP:0040281). (ORPHA:238583)
- Atypical behavior (HP:0000708): Atypical behavior is an abnormality in a person's actions that can be controlled or modulated by the will of the individual. While abnormal behaviors can be difficult to control, they are distinct from other abnormal actions that cannot be affected by the individual's will. Evidence: TAS. Frequency: Frequent (HP:0040282). (ORPHA:238583)
- 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: TAS. Frequency: Frequent (HP:0040282). (ORPHA:238583)
- Excessive salivation (HP:0003781): Excessive production of saliva. Evidence: TAS. Frequency: Frequent (HP:0040282). (ORPHA:238583)
- Decreased CSF homovanillic acid concentration (HP:0003785): Decreased concentration of homovanillic acid (HVA) in the cerebrospinal fluid. HVA is a metabolite of dopamine. Evidence: TAS. Frequency: Frequent (HP:0040282). (ORPHA:238583)
- Neurodevelopmental delay (HP:0012758): Neurodevelopmental delay (NDD) refers to delays in the maturation of the brain and central nervous system; infants and young children with NDD may experience delays in the development of one or more skills including gross motor abilities, fine-motor coordination, language abilities and ability to solve increasingly complex problems. Evidence: TAS. Frequency: Frequent (HP:0040282). (ORPHA:238583)
- Abnormal circulating neopterin concentration (HP:0040206): Any deviation from the normal concentration of neopterin in the blood circulation. Evidence: TAS. Frequency: Frequent (HP:0040282). (ORPHA:238583)
- Abnormal circulating biopterin concentration (HP:0040210): A deviation from the normal concentration of biopterin in the blood circulation. Evidence: TAS. Frequency: Frequent (HP:0040282). (ORPHA:238583)
- Abnormal urinary nitrogen compound level (HP:0040416): The amount of a nitrogen compound in the urine, normalized for urine concentration, is outside of normal limits. Evidence: TAS. Frequency: Frequent (HP:0040282). (ORPHA:238583)
- Microcephaly (HP:0000252): Head circumference below 2 standard deviations below the mean for age and gender. Evidence: TAS. Frequency: Occasional (HP:0040283). (ORPHA:238583)
- Delayed speech and language development (HP:0000750): A degree of language development that is significantly below the norm for a child of a specified age. Evidence: TAS. Frequency: Occasional (HP:0040283). (ORPHA:238583)
- 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: TAS. Frequency: Occasional (HP:0040283). (ORPHA:238583)
- 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: TAS. Frequency: Occasional (HP:0040283). (ORPHA:238583)
- Parkinsonism (HP:0001300): Characteristic neurologic anomaly resulting from degeneration of dopamine-generating cells in the substantia nigra, a region of the midbrain, characterized clinically by shaking, rigidity, slowness of movement and difficulty with walking and gait. Evidence: TAS. Frequency: Occasional (HP:0040283). (ORPHA:238583)
- 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: TAS. Frequency: Occasional (HP:0040283). (ORPHA:238583)
- Basal ganglia calcification (HP:0002135): The presence of calcium deposition affecting one or more structures of the basal ganglia. Evidence: TAS. Frequency: Occasional (HP:0040283). (ORPHA:238583)
- Sleep disturbance (HP:0002360): An abnormal pattern in the quality, quantity, or characteristics of sleep. Evidence: TAS. Frequency: Occasional (HP:0040283). (ORPHA:238583)
- 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: TAS. Frequency: Occasional (HP:0040283). (ORPHA:238583)
- Hypomagnesemia (HP:0002917): The concentration of magnesium in the blood circulation is below the lower limit of normal. Evidence: TAS. Frequency: Occasional (HP:0040283). (ORPHA:238583)
- Maturity-onset diabetes of the young (HP:0004904): The term Maturity-onset diabetes of the young (MODY) was initially used for patients diagnosed with fasting hyperglycemia that could be treated without insulin for more than two years, where the initial diagnosis was made at a young age (under 25 years). Thus, MODY combines characteristics of type 1 diabetes (young age at diagnosis) and type 2 diabetes (less insulin dependence than type 1 diabetes). The term MODY is now most often used to refer to a group of monogenic diseases with these characteristics. Here, the term is used to describe hyperglycemia diagnosed at a young age with no or minor insulin dependency, no evidence of insulin resistance, and lack of evidence of autoimmune destruction of the beta cells. Evidence: TAS. Frequency: Occasional (HP:0040283). (ORPHA:238583)
- Oculogyric crisis (HP:0010553): An acute dystonic reaction with blepharospasm, periorbital twitches, and protracted fixed staring episodes. There may be a maximal upward deviation of the eyes in the sustained fashion. Oculogyric crisis can be triggered by a number of factors including neuroleptic medications. Evidence: TAS. Frequency: Occasional (HP:0040283). (ORPHA:238583)
- Elevated urinary 7-biopterin level (HP:0033594): An abnormally increased amount of 7-biopterin in the urine. Evidence: TAS. Frequency: Occasional (HP:0040283). (ORPHA:238583)
- Cognitive impairment (HP:0100543): Abnormal cognition is characterized by deficits in thinking, reasoning, or remembering. Evidence: TAS. Frequency: Occasional (HP:0040283). (ORPHA:238583)
- Decreased circulating catecholamine concentration (HP:6000482): Concentration of a catecholamine in the blood circulation below the lower limit of normal. Evidence: TAS. Frequency: Occasional (HP:0040283). (ORPHA:238583)
These phenotypes are associated with the disease Hyperphenylalaninemia due to tetrahydrobiopterin deficiency (ORPHA:238583).