- Cerebellar vermis hypoplasia (HP:0001320): Underdevelopment of the vermis of cerebellum. Evidence: TAS. Frequency: Frequent (HP:0040282). (ORPHA:370997)
- Absent speech (HP:0001344): Complete lack of development of speech and language abilities. Evidence: TAS. Frequency: Frequent (HP:0040282). (ORPHA:370997)
- Hypoplasia of the corpus callosum (HP:0002079): Underdevelopment of the corpus callosum. Evidence: TAS. Frequency: Frequent (HP:0040282). (ORPHA:370997)
- Ventriculomegaly (HP:0002119): An increase in size of the ventricular system of the brain. Evidence: TAS. Frequency: Frequent (HP:0040282). (ORPHA:370997)
- Polymicrogyria (HP:0002126): Polymicrogyria is a congenital malformation of the cerebral cortex characterized by abnormal cortical layering (lamination) and an excessive number of small gyri (folds). Evidence: TAS. Frequency: Frequent (HP:0040282). (ORPHA:370997)
- Cerebellar cyst (HP:0002350). Evidence: TAS. Frequency: Frequent (HP:0040282). (ORPHA:370997)
- Abnormal brainstem morphology (HP:0002363): An anomaly of the brainstem. Evidence: TAS. Frequency: Frequent (HP:0040282). (ORPHA:370997)
- Leukodystrophy (HP:0002415): Leukodystrophy refers to deterioration of white matter of the brain resulting from degeneration of myelin sheaths in the CNS. Their basic defect is directly related to the synthesis and maintenance of myelin membranes. Symmetric white matter involvement at MRI is a typical finding in patients with leukodystrophies. Evidence: TAS. Frequency: Frequent (HP:0040282). (ORPHA:370997)
- Poor head control (HP:0002421): Difficulty to maintain correct position of the head while standing or sitting. Infant head lag is observed when the head seems to flop around or lags posteriorly behind the trunk. Several articles have maintained that head lag should be absent by age 3 to 4 months. Evidence: TAS. Frequency: Frequent (HP:0040282). (ORPHA:370997)
- 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: Frequent (HP:0040282). (ORPHA:370997)
- Abnormal pons morphology (HP:0007361): A structural abnormality of the pons. Evidence: TAS. Frequency: Frequent (HP:0040282). (ORPHA:370997)
- 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:370997)
- Severe intellectual disability (HP:0010864): Severe intellectual disability (ID) is defined as a type of ID characterized by severely sub-average adaptive functioning and intellectual functioning, with an intelligence quotient (IQ) the range of 20-34. Evidence: TAS. Frequency: Frequent (HP:0040282). (ORPHA:370997)
- EEG with focal spike waves (HP:0011197): EEG with focal sharp transient waves of a duration less than 80 msec followed by a slow wave. Evidence: TAS. Frequency: Frequent (HP:0040282). (ORPHA:370997)
- Severe global developmental delay (HP:0011344): A severe delay in the achievement of motor or mental milestones in the domains of development of a child. Evidence: TAS. Frequency: Frequent (HP:0040282). (ORPHA:370997)
- Delayed ability to sit (HP:0025336): A failure to achieve the ability to sit at an appropriate developmental stage. Most children sit with support at 6 months of age and sit steadily without support at 9 months of age. Evidence: TAS. Frequency: Frequent (HP:0040282). (ORPHA:370997)
- Hypoglycosylation of alpha-dystroglycan (HP:0030046): A reduction in the degree of glycosylation of alpha-dystroglycan in muscle tissue. Evidence: TAS. Frequency: Frequent (HP:0040282). (ORPHA:370997)
- Agyria (HP:0031882): A congenital abnormality of the cerebral hemisphere characterized by lack of gyrations (convolutions) of the cerebral cortex. Agyria is defined as cortical regions lacking gyration with sulci great than 3 cm apart and cerebral cortex thicker than 5 mm. Evidence: TAS. Frequency: Frequent (HP:0040282). (ORPHA:370997)
- Delayed ability to walk (HP:0031936): A failure to achieve the ability to walk at an appropriate developmental stage. Most children learn to walk in a series of stages, and learn to walk short distances independently between 12 and 15 months. Evidence: TAS. Frequency: Frequent (HP:0040282). (ORPHA:370997)
- Cataract (HP:0000518): A cataract is an opacity or clouding that develops in the crystalline lens of the eye or in its capsule. Evidence: TAS. Frequency: Occasional (HP:0040283). (ORPHA:370997)
- 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:370997)
- Buphthalmos (HP:0000557): Diffusely large eye (with megalocornea) associated with glaucoma. Evidence: TAS. Frequency: Occasional (HP:0040283). (ORPHA:370997)
- High myopia (HP:0011003): A severe form of myopia with greater than -6.00 diopters. Evidence: TAS. Frequency: Occasional (HP:0040283). (ORPHA:370997)
These phenotypes are associated with the disease Muscle-eye-brain disease with bilateral multicystic leucodystrophy (ORPHA:370997).