- Visual impairment (HP:0000505): Visual impairment (or vision impairment) is vision loss (of a person) to such a degree as to qualify as an additional support need through a significant limitation of visual capability resulting from either disease, trauma, or congenital or degenerative conditions that cannot be corrected by conventional means, such as refractive correction, medication, or surgery. Evidence: TAS. Frequency: Very frequent (HP:0040281). (ORPHA:1187)
- Blindness (HP:0000618): Blindness is the condition of lacking visual perception defined as a profound reduction in visual perception. On the 6m visual acuity scale, blindness is defined as less than 3/60. On the 20ft visual acuity scale, blindness is defined as less than 20/400. On the decimal visual acuity scale, blindness is defined as less than 0.05. Blindness is typically characterized by a visual field of no greater than 10 degrees in radius around central fixation. Evidence: TAS. Frequency: Very frequent (HP:0040281). (ORPHA:1187)
- 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: Very frequent (HP:0040281). (ORPHA:1187)
- Muscle weakness (HP:0001324): Reduced strength of muscles. Evidence: TAS. Frequency: Very frequent (HP:0040281). (ORPHA:1187)
- Mutism (HP:0002300): Complete lack of speech or verbal communication in a person despite attempts to engage in conversation. Mutism as a phenomena assumes the individual has previous capacity for speech and in the pediatric population it assumes that the person is past the age of typical language development. Evidence: TAS. Frequency: Very frequent (HP:0040281). (ORPHA:1187)
- Recurrent infections (HP:0002719): Increased susceptibility to infections as manifested by repeated bouts of infection. Evidence: TAS. Frequency: Very frequent (HP:0040281). (ORPHA:1187)
- Recurrent upper respiratory tract infections (HP:0002788): An increased susceptibility to upper respiratory tract infections as manifested by a history of recurrent upper respiratory tract infections (running ears - otitis, sinusitis, pharyngitis, tonsillitis). Evidence: TAS. Frequency: Very frequent (HP:0040281). (ORPHA:1187)
- Decreased motor nerve conduction velocity (HP:0003431): A type of decreased nerve conduction velocity that affects the motor neuron. Evidence: TAS. Frequency: Very frequent (HP:0040281). (ORPHA:1187)
- EMG: chronic denervation signs (HP:0003444): Evidence of chronic denervation on electromyography. Evidence: TAS. Frequency: Very frequent (HP:0040281). (ORPHA:1187)
- Severe demyelination of the white matter (HP:0007258): A severe loss of myelin from nerve fibers in the central nervous system. Evidence: TAS. Frequency: Very frequent (HP:0040281). (ORPHA:1187)
- Abnormality of somatosensory evoked potentials (HP:0007377): An abnormality of somatosensory evoked potentials (SSEP), i.e., of the electrical signals of sensation going from the body to the brain in response to a defined stimulus. Recording electrodes are placed over the scalp, spine, and peripheral nerves proximal to the stimulation site. Clinical studies generally use electrical stimulation of peripheral nerves to elicit potentials. SSEP testing determines whether peripheral sensory nerves are able to transmit sensory information like pain, temperature, and touch to the brain. Abnormal SSEPs can result from dysfunction at the level of the peripheral nerve, plexus, spinal root, spinal cord, brain stem, thalamocortical projections, or primary somatosensory cortex. Evidence: TAS. Frequency: Very frequent (HP:0040281). (ORPHA:1187)
- Congenital sensorineural hearing impairment (HP:0008527): A type of hearing impairment caused by an abnormal functionality of the cochlear nerve with congenital onset. Evidence: TAS. Frequency: Very frequent (HP:0040281). (ORPHA:1187)
- Abnormal erythrocyte enzyme concentration or activity (HP:0030272): An altered level of any enzyme to act as catalysts within erythrocytes. This term includes changes due to altered activity of an enzyme. Evidence: TAS. Frequency: Very frequent (HP:0040281). (ORPHA:1187)
- Severe infection (HP:0032169): A type of infection that is regarded as a sign of a pathological susceptibility to infection because of unusual severity or intensity of the infection. Evidence: TAS. Frequency: Very frequent (HP:0040281). (ORPHA:1187)
- Neck muscle weakness (HP:0000467): Decreased strength of the neck musculature. Evidence: TAS. Frequency: Frequent (HP:0040282). (ORPHA:1187)
- Nystagmus (HP:0000639): Rhythmic, involuntary oscillations of one or both eyes related to abnormality in fixation, conjugate gaze, or vestibular mechanisms. Evidence: TAS. Frequency: Frequent (HP:0040282). (ORPHA:1187)
- 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:1187)
- 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:1187)
- Motor delay (HP:0001270): A type of Developmental delay characterized by a delay in acquiring motor skills. Evidence: TAS. Frequency: Frequent (HP:0040282). (ORPHA:1187)
- Areflexia (HP:0001284): Absence of neurologic reflexes such as the knee-jerk reaction. Evidence: TAS. Frequency: Frequent (HP:0040282). (ORPHA:1187)
- 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: Frequent (HP:0040282). (ORPHA:1187)
- Tetraplegia (HP:0002445): Paralysis of all four limbs, and trunk of the body below the level of an associated injury to the spinal cord. The etiology of quadriplegia is similar to that of paraplegia except that the lesion is in the cervical spinal cord rather than in the thoracic or lumbar segments of the spinal cord. Evidence: TAS. Frequency: Frequent (HP:0040282). (ORPHA:1187)
- Hypouricemia (HP:0003537): The concentration of uric acid in the blood circulation is below the lower limit of normal. Evidence: TAS. Frequency: Frequent (HP:0040282). (ORPHA:1187)
- Respiratory failure requiring assisted ventilation (HP:0004887): A state of respiratory distress that requires a life saving intervention in the form of gaining airway access and instituting positive pressure ventilation. Evidence: TAS. Frequency: Frequent (HP:0040282). (ORPHA:1187)
- Spinal cord dorsal column hypomyelination (HP:0008311): Lower than normal amount of myelin in the dorsal (posterior) tract of the spinal cord white matter. Evidence: TAS. Frequency: Frequent (HP:0040282). (ORPHA:1187)
- Axial hypotonia (HP:0008936): Muscular hypotonia (abnormally low muscle tone) affecting the musculature of the trunk. Evidence: TAS. Frequency: Frequent (HP:0040282). (ORPHA:1187)
- Peripheral neuropathy (HP:0009830): Peripheral neuropathy is a general term for any disorder of the peripheral nervous system. The main clinical features used to classify peripheral neuropathy are distribution, type (mainly demyelinating versus mainly axonal), duration, and course. Evidence: TAS. Frequency: Frequent (HP:0040282). (ORPHA:1187)
- EEG with focal epileptiform discharges (HP:0011185): EEG discharges recorded in particular areas of a localized (focal) abnormality in cerebral electrical activity recorded along the scalp by electroencephalography (EEG). Evidence: TAS. Frequency: Frequent (HP:0040282). (ORPHA:1187)
- Profound sensorineural hearing impairment (HP:0011476): Complete loss of hearing related to a sensorineural defect. Evidence: TAS. Frequency: Frequent (HP:0040282). (ORPHA:1187)
- Appendicular hypotonia (HP:0012389): Muscular hypotonia of one or more limbs. Evidence: TAS. Frequency: Frequent (HP:0040282). (ORPHA:1187)
These phenotypes are associated with the disease Lethal ataxia with deafness and optic atrophy (ORPHA:1187).