- Tetraparesis (HP:0002273): Weakness of all four limbs. Evidence: TAS. Frequency: Frequent (HP:0040282). (ORPHA:225154)
- Developmental regression (HP:0002376): Loss of developmental skills, as manifested by loss of developmental milestones. Evidence: TAS. Frequency: Frequent (HP:0040282). (ORPHA:225154)
- Babinski sign (HP:0003487): Upturning of the big toe (and sometimes fanning of the other toes) in response to stimulation of the sole of the foot. If the Babinski sign is present it can indicate damage to the corticospinal tract. Evidence: TAS. Frequency: Frequent (HP:0040282). (ORPHA:225154)
- Basal ganglia gliosis (HP:0006999): Focal proliferation of glial cells in the basal ganglia. Evidence: TAS. Frequency: Frequent (HP:0040282). (ORPHA:225154)
- Atrophy/Degeneration involving the caudate nucleus (HP:0007374). Evidence: TAS. Frequency: Frequent (HP:0040282). (ORPHA:225154)
- Horizontal pendular nystagmus (HP:0007811): Nystagmus consisting of horizontal to-and-fro eye movements of equal velocity. Evidence: TAS. Frequency: Frequent (HP:0040282). (ORPHA:225154)
- 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: Frequent (HP:0040282). (ORPHA:225154)
- 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:225154)
- 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:225154)
- Myoclonus (HP:0001336): Very brief, involuntary random muscular contractions occurring at rest, in response to sensory stimuli, or accompanying voluntary movements. Evidence: TAS. Frequency: Occasional (HP:0040283). (ORPHA:225154)
- Gastroesophageal reflux (HP:0002020): A condition in which the stomach contents leak backwards from the stomach into the esophagus through the lower esophageal sphincter. Evidence: TAS. Frequency: Occasional (HP:0040283). (ORPHA:225154)
- 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: TAS. Frequency: Occasional (HP:0040283). (ORPHA:225154)
- Frequent falls (HP:0002359). Evidence: TAS. Frequency: Occasional (HP:0040283). (ORPHA:225154)
- Cogwheel rigidity (HP:0002396): A type of rigidity in which a muscle responds with cogwheellike jerks to the use of constant force in bending the limb (i.e., it gives way in little, repeated jerks when the muscle is passively stretched). Evidence: TAS. Frequency: Occasional (HP:0040283). (ORPHA:225154)
- Astrocytosis (HP:0002446): Proliferation of astrocytes in the area of a lesion of the central nervous system. Evidence: TAS. Frequency: Occasional (HP:0040283). (ORPHA:225154)
- Loss of ambulation (HP:0002505): Inability to walk in a person who previous had the ability to walk. Evidence: TAS. Frequency: Occasional (HP:0040283). (ORPHA:225154)
- Upper limb muscle weakness (HP:0003484): Weakness of the muscles of the arms. Evidence: TAS. Frequency: Occasional (HP:0040283). (ORPHA:225154)
- Basal ganglia cysts (HP:0006799). Evidence: TAS. Frequency: Occasional (HP:0040283). (ORPHA:225154)
- Lower limb muscle weakness (HP:0007340): Weakness of the muscles of the legs. Evidence: TAS. Frequency: Occasional (HP:0040283). (ORPHA:225154)
- Undetectable light- and dark-adapted electroretinogram (HP:0007688): Absence of the combined rod-and-cone response on electroretinogram. Evidence: TAS. Frequency: Occasional (HP:0040283). (ORPHA:225154)
- Small basal ganglia (HP:0012697): Decreased size of the basal ganglia. Evidence: TAS. Frequency: Occasional (HP:0040283). (ORPHA:225154)
- Optic atrophy (HP:0000648): Atrophy of the optic nerve. Optic atrophy results from the death of the retinal ganglion cell axons that comprise the optic nerve and manifesting as a pale optic nerve on fundoscopy. Evidence: TAS. Frequency: Frequent (HP:0040282). (ORPHA:225154)
- 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: Frequent (HP:0040282). (ORPHA:225154)
- Ataxia (HP:0001251): Ataxia refers to impaired coordination of voluntary muscle movement. Cerebellar ataxia refers to ataxia due to dysfunction of the cerebellum. This causes a variety of elementary neurological deficits including asynergy (lack of coordination between muscles, limbs and joints), dysmetria (lack of ability to judge distances that can lead to under- or overshoot in grasping movements), and dysdiadochokinesia (inability to perform rapid movements requiring antagonizing muscle groups to be switched on and off repeatedly). Evidence: TAS. Frequency: Frequent (HP:0040282). (ORPHA:225154)
- Mild intellectual disability (HP:0001256): Mild intellectual disability (ID) is defined as a type of ID characterized by mildly sub-average adaptive functioning and intellectual functioning, with an intelligence quotient (IQ) the range of 50-69. Evidence: TAS. Frequency: Frequent (HP:0040282). (ORPHA:225154)
- Spasticity (HP:0001257): A motor disorder characterized by a velocity-dependent increase in tonic stretch reflexes with increased muscle tone, exaggerated (hyperexcitable) tendon reflexes. Evidence: TAS. Frequency: Frequent (HP:0040282). (ORPHA:225154)
- Dysarthria (HP:0001260): Dysarthric speech is a general description referring to a neurological speech disorder characterized by poor articulation. Depending on the involved neurological structures, dysarthria may be further classified as spastic, flaccid, ataxic, hyperkinetic and hypokinetic, or mixed. Evidence: TAS. Frequency: Frequent (HP:0040282). (ORPHA:225154)
- Choreoathetosis (HP:0001266): Involuntary movements characterized by both athetosis (inability to sustain muscles in a fixed position) and chorea (widespread jerky arrhythmic movements). Evidence: TAS. Frequency: Frequent (HP:0040282). (ORPHA:225154)
- Spastic tetraparesis (HP:0001285): Spastic weakness affecting all four limbs. Evidence: TAS. Frequency: Frequent (HP:0040282). (ORPHA:225154)
- 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:225154)
- 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:225154)
- Hyperreflexia (HP:0001347): Hyperreflexia is the presence of hyperactive stretch reflexes of the muscles. Evidence: TAS. Frequency: Frequent (HP:0040282). (ORPHA:225154)
- 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:225154)
- Dysphagia (HP:0002015): Difficulty in swallowing. Evidence: TAS. Frequency: Frequent (HP:0040282). (ORPHA:225154)
- Gait ataxia (HP:0002066): A type of ataxia characterized by the impairment of the ability to coordinate the movements required for normal walking. Gait ataxia is characteirzed by a wide-based staggering gait with a tendency to fall. Evidence: TAS. Frequency: Frequent (HP:0040282). (ORPHA:225154)
- Abnormal speech pattern (HP:0002167): An abnormality in the sound (volume) or cadence (rate) of speech. Evidence: TAS. Frequency: Frequent (HP:0040282). (ORPHA:225154)
These phenotypes are associated with the disease Familial infantile bilateral striatal necrosis (ORPHA:225154).