- Gait disturbance (HP:0001288): The term gait disturbance can refer to any disruption of the ability to walk. Evidence: TAS. Frequency: Frequent (HP:0040282). (ORPHA:778)
- Progressive microcephaly (HP:0000253): Progressive microcephaly is diagnosed when the head circumference falls progressively behind age- and gender-dependent norms. Evidence: TAS. Frequency: Very frequent (HP:0040281). (ORPHA:778)
- Motor stereotypy (HP:0000733): Use of the same abnormal action in response to certain triggers or at random. They may be used as a way to regulate one's internal state but must otherwise have no apparent functional purpose. Evidence: TAS. Frequency: Very frequent (HP:0040281). (ORPHA:778)
- 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: TAS. Frequency: Very frequent (HP:0040281). (ORPHA:778)
- Gait disturbance (HP:0001288): The term gait disturbance can refer to any disruption of the ability to walk. Evidence: TAS. Frequency: Very frequent (HP:0040281). (ORPHA:778)
- Absent speech (HP:0001344): Complete lack of development of speech and language abilities. Evidence: TAS. Frequency: Very frequent (HP:0040281). (ORPHA:778)
- Developmental regression (HP:0002376): Loss of developmental skills, as manifested by loss of developmental milestones. Evidence: TAS. Frequency: Very frequent (HP:0040281). (ORPHA:778)
- Abnormal pattern of respiration (HP:0002793): An anomaly of the rhythm or depth of breathing. Evidence: TAS. Frequency: Very frequent (HP:0040281). (ORPHA:778)
- Progressive language deterioration (HP:0007064): Progressive loss of previously present language abilities. Evidence: TAS. Frequency: Very frequent (HP:0040281). (ORPHA:778)
- Stereotypical hand wringing (HP:0012171): Habitual clasping and wringing of the hands in the middle of the body, similar to a hand-washing movement. Evidence: TAS. Frequency: Very frequent (HP:0040281). (ORPHA:778)
- High-pitched cry (HP:0025430): A type of crying in an abnormally high-pitched voice. Evidence: TAS. Frequency: Very frequent (HP:0040281). (ORPHA:778)
- 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: Frequent (HP:0040282). (ORPHA:778)
- 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: Frequent (HP:0040282). (ORPHA:778)
- Failure to thrive (HP:0001508): Failure to thrive (FTT) refers to a child whose physical growth is substantially below the norm. Evidence: TAS. Frequency: Frequent (HP:0040282). (ORPHA:778)
- Growth delay (HP:0001510): A deficiency or slowing down of growth pre- and postnatally. Evidence: TAS. Frequency: Frequent (HP:0040282). (ORPHA:778)
- Bradykinesia (HP:0002067): Bradykinesia literally means slow movement, and is used clinically to denote a slowness in the execution of movement (in contrast to hypokinesia, which is used to refer to slowness in the initiation of movement). Evidence: TAS. Frequency: Frequent (HP:0040282). (ORPHA:778)
- EEG abnormality (HP:0002353): Abnormality observed by electroencephalogram (EEG), which is used to record of the brain's spontaneous electrical activity from multiple electrodes placed on the scalp. Evidence: TAS. Frequency: Frequent (HP:0040282). (ORPHA:778)
- Skeletal muscle atrophy (HP:0003202): The presence of skeletal muscular atrophy (which is also known as amyotrophy). Evidence: TAS. Frequency: Frequent (HP:0040282). (ORPHA:778)
- Bruxism (HP:0003763): Bruxism is characterized by the grinding of the teeth including the clenching of the jaw and typically occur during sleep. Evidence: TAS. Frequency: Frequent (HP:0040282). (ORPHA:778)
- Abnormal muscle tone (HP:0003808). Evidence: TAS. Frequency: Frequent (HP:0040282). (ORPHA:778)
- Limb apraxia (HP:0030217): Difficulty in performing the correct execution of limbs movements in absence of motor impairment. Evidence: TAS. Frequency: Frequent (HP:0040282). (ORPHA:778)
- Coldness (HP:0033850): Relative coldness of a body part to palpitation, often acccompanied by feelings of coldness. Evidence: TAS. Frequency: Frequent (HP:0040282). (ORPHA:778)
- Agitation (HP:0000713): A state of excessive motor activity that is associated with mental distress or a feeling of substantial unease or inner tension. Distinguished from restlessness by the increased level of emotional distress and negative intensity of the experience. Agitation has a significant level of physical activity that is typically threatening to the self or others. Evidence: TAS. Frequency: Occasional (HP:0040283). (ORPHA:778)
- Cholecystitis (HP:0001082): The presence of inflammatory changes in the gallbladder. Evidence: TAS. Frequency: Occasional (HP:0040283). (ORPHA:778)
- Hyperammonemia (HP:0001987): An increased concentration of ammonia in the blood. Evidence: TAS. Frequency: Occasional (HP:0040283). (ORPHA:778)
- 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: TAS. Frequency: Occasional (HP:0040283). (ORPHA:778)
- Sleep disturbance (HP:0002360): An abnormal pattern in the quality, quantity, or characteristics of sleep. Evidence: TAS. Frequency: Occasional (HP:0040283). (ORPHA:778)
- Increased CSF lactate (HP:0002490): Increased concentration of lactate in the cerebrospinal fluid. Evidence: TAS. Frequency: Occasional (HP:0040283). (ORPHA:778)
- Inability to walk (HP:0002540): Incapability to ambulate. Evidence: TAS. Frequency: Occasional (HP:0040283). (ORPHA:778)
- Scoliosis (HP:0002650): The presence of an abnormal lateral curvature of the spine. Evidence: TAS. Frequency: Occasional (HP:0040283). (ORPHA:778)
- Increased circulating pyruvate concentration (HP:0003542): The concentration of pyruvate in the blood circulation is above the upper limit of normal. Evidence: TAS. Frequency: Occasional (HP:0040283). (ORPHA:778)
- Floppy infant (HP:0008947): Floppiness/hypotonia is defined as reduced resistance to passive movement of joints. Physical examination of floppy/hypotonic infants shows head lag, lack of shoulder and elbow muscle contraction on traction response, inability to tighten the shoulder girdle muscles (or slipping through) when held under the axillae, scarf sign (when the arm is pulled to the opposite side, the arm wraps around the neck with the elbow crossing midline), hyperdorsiflexion of the feet, easy apposition of the thumb against the forearm, feet touching the cheek with ease and without discomfort, frog leg position, and inverted U sign on ventral suspension (head, arms, and legs hanging down without elbow or knee flexion and the trunk rounded in a dome shape). Evidence: TAS. Frequency: Occasional (HP:0040283). (ORPHA:778)
- Abnormal autonomic nervous system physiology (HP:0012332): A functional abnormality of the autonomic nervous system. Evidence: TAS. Frequency: Occasional (HP:0040283). (ORPHA:778)
- Increased serum leptin (HP:0031793): An increased concentration of leptin in the blood. Evidence: TAS. Frequency: Occasional (HP:0040283). (ORPHA:778)
- Abnormal CSF pyruvate family amino acid concentration (HP:0500231): Any deviation from the normal concentration of pyruvate-family amino acids in the cerebrospinal fluid. Evidence: TAS. Frequency: Occasional (HP:0040283). (ORPHA:778)
- Primary microcephaly (HP:0011451): Head circumference below 2 standard deviations below the mean for age and gender at birth. Evidence: TAS. Frequency: Very rare (HP:0040284). (ORPHA:778)
These phenotypes are associated with the disease Rett syndrome (ORPHA:778).