- Scanning speech (HP:0002168): An abnormal pattern of speech in which the words are as if measured or scanned; there is a pause after every syllable, and the syllables themselves are pronounced slowly. Evidence: IEA. (OMIM:607454)
- Strabismus (HP:0000486): A misalignment of the eyes so that the visual axes deviate from bifoveal fixation. The classification of strabismus may be based on a number of features including the relative position of the eyes, whether the deviation is latent or manifest, intermittent or constant, concomitant or otherwise and according to the age of onset and the relevance of any associated refractive error. Evidence: PCS. Frequency: 1/5. (PMID:33851480)
- Middle age onset (HP:0003596): A type of adult onset with onset of symptoms at the age of 40 to 60 years. Evidence: PCS. Frequency: 3/5. (PMID:33851480)
- Delayed CNS myelination (HP:0002188): Delayed myelination in the central nervous system. Evidence: PCS. Frequency: 1/5. (PMID:33851480)
- 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: 1/5. (PMID:33851480)
- Cerebellar atrophy (HP:0001272): Cerebellar atrophy is defined as a cerebellum with initially normal structures, in a posterior fossa with normal size, which displays enlarged fissures (interfolial spaces) in comparison to the foliae secondary to loss of tissue. Cerebellar atrophy implies irreversible loss of tissue and result from an ongoing progressive disease until a final stage is reached or a single injury, e.g. an intoxication or infectious event. Evidence: PCS. Frequency: 3/4. (PMID:33851480)
- 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: PCS. Frequency: 5/5. (PMID:33851480)
- 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: PCS. Frequency: 5/5. (PMID:33851480)
- Opsoclonus (HP:0010543): Bursts of large-amplitude multidirectional saccades without intersaccadic interval. Evidence: PCS. Frequency: 1/5. (PMID:33851480)
- Dysgraphia (HP:0010526): A writing disability in the absence of motor or sensory deficits of the upper extremities, resulting in an impairment in the ability to write regardless of the ability to read and not due to intellectual impairment. Evidence: IEA. (OMIM:607454)
- Intention tremor (HP:0002080): A type of kinetic tremor that occurs during target directed movement is called intention tremor. That is, an oscillatory cerebellar ataxia that tends to be absent when the limbs are inactive and during the first part of voluntary movement but worsening as the movement continues and greater precision is required (e.g., in touching a target such as the patient's nose or a physician's finger). Evidence: PCS. Frequency: 2/5. (PMID:33851480)
- Cognitive impairment (HP:0100543): Abnormal cognition is characterized by deficits in thinking, reasoning, or remembering. Evidence: IEA. (OMIM:607454)
- Nystagmus (HP:0000639): Rhythmic, involuntary oscillations of one or both eyes related to abnormality in fixation, conjugate gaze, or vestibular mechanisms. Evidence: PCS. Frequency: 2/5. (PMID:33851480)
- Childhood onset (HP:0011463): Onset of disease at the age of between 1 and 5 years. Evidence: PCS. Frequency: 1/5. (PMID:33851480)
- Aggressive behavior (HP:0000718): Behavior or an act aimed at harming a person, animal, or physical property (e.g., acts of physical violence; shouting, swearing, and using harsh language; slashing someone's tires). Evidence: TAS. (OMIM:607454)
- Slow saccadic eye movements (HP:0000514): An abnormally slow velocity of the saccadic eye movements. Evidence: TAS. (OMIM:607454)
- Mental deterioration (HP:0001268): Loss of previously present mental abilities, generally in adults. Evidence: PCS. Frequency: 3/5. (PMID:33851480)
- 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: PCS. Frequency: 2/5. (PMID:33851480)
- Neonatal onset (HP:0003623): Onset of signs or symptoms of disease within the first 28 days of life. Evidence: PCS. Frequency: 1/5. (PMID:33851480)
- Hyporeflexia (HP:0001265): Reduction of neurologic reflexes such as the knee-jerk reaction. Evidence: IEA. (OMIM:607454)
- 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. (OMIM:607454)
- 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: IEA. (OMIM:607454)
- 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: PCS. Frequency: 2/5. (PMID:33851480)
- 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: 2/5. (PMID:33851480)
- Postural tremor (HP:0002174): A type of tremors that is triggered by holding a limb in a fixed position. Evidence: PCS. Frequency: 3/5. (PMID:33851480)
- Progressive cerebellar ataxia (HP:0002073). Evidence: IEA. (OMIM:607454)
- Limb ataxia (HP:0002070): A kind of ataxia that affects movements of the extremities. Evidence: IEA. (OMIM:607454)
- Abnormality of extrapyramidal motor function (HP:0002071): A neurological condition related to lesions of the basal ganglia leading to typical abnormalities including akinesia (inability to initiate changes in activity and perform volitional movements rapidly and easily), muscular rigidity (continuous contraction of muscles with constant resistance to passive movement), chorea (widespread arrhythmic movements of a forcible, rapid, jerky, and restless nature), athetosis (inability to sustain the muscles of the fingers, toes, or other group of muscles in a fixed position), and akathisia (inability to remain motionless). Evidence: IEA. (OMIM:607454)
- Impulsivity (HP:0100710): Acting on the spur of the moment or on a momentary basis without consideration of outcomes; having difficulty establishing or following plans; experiencing a sense of urgency and engaging in behavior that is uninhibited, cannot be inhibited, and is uncontrolled. The possibility of repression is inconceivable. Evidence: PCS. Frequency: 1/5. (PMID:33851480)
- Microsaccadic pursuit (HP:0007792). Evidence: IEA. (OMIM:607454)
- Akinesia (HP:0002304): Inability to initiate changes in activity or movement and to perform ordinary volitional movements rapidly and easily. Evidence: IEA. (OMIM:607454)
- Apathy (HP:0000741): Apathy is a quantitative reduction of interest, motivation and the initiation and persistence of goal-directed behavior, where often the accompanying emotions, thoughts, and social interactions are also diminished. The individual is typically non-reactive to provocations, positive or negative, and appears to not care. Distinguished from lethargy which involves lack of physical or mental energy. Evidence: TAS. (OMIM:607454)
- Autosomal dominant inheritance (HP:0000006): 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 heterozygotes. In the context of medical genetics, an autosomal dominant disorder is caused when a single copy of the mutant allele is present. Males and females are affected equally, and can both transmit the disorder with a risk of 50% for each child of inheriting the mutant allele. Evidence: PCS. (PMID:33851480)
- Slowly progressive (HP:0003677): Applies to a disease manifestation that only slowly increases in scope or severity over the course of time. Evidence: IEA. (OMIM:607454)
- Hypermetric saccades (HP:0007338): A saccade that overshoots the target with the dynamic saccade. Evidence: PCS. Frequency: 2/5. (PMID:33851480)
These phenotypes are associated with the disease spinocerebellar ataxia type 21 (OMIM:607454).