- 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: Very frequent (HP:0040281). (ORPHA:370022)
- Dilated fourth ventricle (HP:0002198): An abnormal dilatation of the fourth cerebral ventricle. Evidence: TAS. Frequency: Very frequent (HP:0040281). (ORPHA:370022)
- Moderate intellectual disability (HP:0002342): Moderate intellectual disability (ID) is defined as a type of ID characterized by moderately sub-average adaptive functioning and intellectual functioning, with an intelligence quotient (IQ) the range of 35-49. Evidence: TAS. Frequency: Very frequent (HP:0040281). (ORPHA:370022)
- Cerebellar cyst (HP:0002350). Evidence: TAS. Frequency: Very frequent (HP:0040281). (ORPHA:370022)
- Cerebellar dysplasia (HP:0007033): Cerebellar dysplasia (abnormal growth or development) is defined by abnormal cerebellar foliation, white matter arborization, and gray-white matter junction. Cerebellar dysplasia is a neuroimaging finding that describes abnormalities of both the cerebellar cortex and white matter and is associated with variable neurodevelopmental outcome. Dysplasia may globally involve the cerebellum or affect only one cerebellar hemisphere. In addition, cerebellar dysplasia may be associated with cortical/subcortical cysts. Evidence: TAS. Frequency: Very frequent (HP:0040281). (ORPHA:370022)
- Cognitive impairment (HP:0100543): Abnormal cognition is characterized by deficits in thinking, reasoning, or remembering. Evidence: TAS. Frequency: Very frequent (HP:0040281). (ORPHA:370022)
- 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: TAS. Frequency: Frequent (HP:0040282). (ORPHA:370022)
- Myopia (HP:0000545): An abnormality of refraction characterized by the ability to see objects nearby clearly, while objects in the distance appear blurry. Evidence: TAS. Frequency: Frequent (HP:0040282). (ORPHA:370022)
- Amblyopia (HP:0000646): Reduced visual acuity that is uncorrectable by lenses in the absence of detectable anatomic defects in the eye or visual pathways. Evidence: TAS. Frequency: Frequent (HP:0040282). (ORPHA:370022)
- Oculomotor apraxia (HP:0000657): Ocular motor apraxia is a deficiency in voluntary, horizontal, lateral, fast eye movements (saccades) with retention of slow pursuit movements. The inability to follow objects visually is often compensated by head movements. There may be decreased smooth pursuit, and cancelation of the vestibulo-ocular reflex. Evidence: TAS. Frequency: Frequent (HP:0040282). (ORPHA:370022)
- Retinal atrophy (HP:0001105): A nonspecific term denoting wasting, especially as a result of degeneration, of the retinal pigment epithelium (RPE) and neurosensory retinal cells. Evidence: TAS. Frequency: Frequent (HP:0040282). (ORPHA:370022)
- 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: Frequent (HP:0040282). (ORPHA:370022)
- Abnormal brainstem morphology (HP:0002363): An anomaly of the brainstem. Evidence: TAS. Frequency: Frequent (HP:0040282). (ORPHA:370022)
- Inferior cerebellar vermis hypoplasia (HP:0007068): Underdevelopment of the inferior portion of the vermis of cerebellum. Evidence: TAS. Frequency: Frequent (HP:0040282). (ORPHA:370022)
- Elongated superior cerebellar peduncle (HP:0011933): Increased length of the superior cerebellar peduncle. Evidence: TAS. Frequency: Frequent (HP:0040282). (ORPHA:370022)
- Hypermetropia (HP:0000540): An abnormality of refraction characterized by the ability to see objects in the distance clearly, while objects nearby appear blurry. Evidence: TAS. Frequency: Occasional (HP:0040283). (ORPHA:370022)
- Retinal dystrophy (HP:0000556): Retinal dystrophy is an abnormality of the retina associated with a hereditary process. Retinal dystrophies are defined by their predominantly monogenic inheritance and they are frequently associated with loss or dysfunction of photoreceptor cells as a primary or secondary event. Evidence: TAS. Frequency: Occasional (HP:0040283). (ORPHA:370022)
- Nystagmus (HP:0000639): Rhythmic, involuntary oscillations of one or both eyes related to abnormality in fixation, conjugate gaze, or vestibular mechanisms. Evidence: TAS. Frequency: Occasional (HP:0040283). (ORPHA:370022)
- 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: Occasional (HP:0040283). (ORPHA:370022)
- Head titubation (HP:0002599): A head tremor of moderate speed (3 to 4 Hz) in the anterior-posterior direction. Evidence: TAS. Frequency: Occasional (HP:0040283). (ORPHA:370022)
- Elevated circulating creatine kinase activity (HP:0003236): The activity of creatine kinase in the blood circulation is above the upper limit of normal. Evidence: TAS. Frequency: Occasional (HP:0040283). (ORPHA:370022)
- 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: Very rare (HP:0040284). (ORPHA:370022)
These phenotypes are associated with the disease Ataxia-intellectual disability-oculomotor apraxia-cerebellar cysts syndrome (ORPHA:370022).