- Bilateral tonic-clonic seizure (HP:0002069): A bilateral tonic-clonic seizure is a seizure defined by a tonic (bilateral increased tone, lasting seconds to minutes) and then a clonic (bilateral sustained rhythmic jerking) phase. Evidence: PCS. Frequency: 1/2. (PMID:26467484)
- Narrow forehead (HP:0000341): Width of the forehead or distance between the frontotemporales is more than two standard deviations below the mean (objective); or apparently narrow intertemporal region (subjective). Evidence: PCS. Frequency: 1/1. (PMID:30985297)
- Action tremor (HP:0002345): A tremor present when the limbs are active, either when outstretched in a certain position or throughout a voluntary movement. Evidence: PCS. Frequency: 1/2. (PMID:26467484)
- Bradykinesia (HP:0002067): Bradykinesia literally means slow movement, and is used clinically to denote a slowness in the execution of movement (in contrast to hypokinesia, which is used to refer to slowness in the initiation of movement). Evidence: PCS. Frequency: 2/2. (PMID:26467484)
- Delayed CNS myelination (HP:0002188): Delayed myelination in the central nervous system. Evidence: PCS. Frequency: 1/1. (PMID:30985297)
- Astereognosis (HP:0010527): Tactile agnosia refers to the inability to recognize objects by touch, while the inability to discriminate shape and size by touch is also a related condition. Evidence: PCS. Frequency: 2/2. (PMID:26467484)
- Apraxia (HP:0002186): A defect in the understanding of complex motor commands and in the execution of certain learned movements, i.e., deficits in the cognitive components of learned movements. Evidence: PCS. Frequency: 2/2. (PMID:26467484)
- 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: 1/2. (PMID:26467484)
- Impaired tandem gait (HP:0031629): Reduced ability to walk in a straight line while placing the feet heel to toe. Evidence: PCS. Frequency: 1/2. (PMID:26467484)
- Seizure (HP:0001250): A seizure is an intermittent abnormality of nervous system physiology characterized by a transient occurrence of signs and/or symptoms due to abnormal excessive or synchronous neuronal activity in the brain. Evidence: PCS. Frequency: 1/1. (PMID:30985297)
- 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: PCS. Frequency: 1/2. (PMID:26467484)
- Infantile onset (HP:0003593): Onset of signs or symptoms of disease between 28 days to one year of life. Evidence: PCS. (PMID:26467484)
- Slurred speech (HP:0001350): Abnormal coordination of muscles involved in speech. Evidence: PCS. Frequency: 1/2. (PMID:26467484)
- Agraphesthesia (HP:0011812): Impaired ability to recognize letters or numbers drawn by an examiner's fingertip on the patient's skin (the patients eyes are closed or covered throughout this examination). Evidence: PCS. Frequency: 2/2. (PMID:26467484)
- Motor delay (HP:0001270): A type of Developmental delay characterized by a delay in acquiring motor skills. Evidence: PCS. (PMID:15746149)
- Thin corpus callosum (HP:0033725): An abnormally thin corpus callous, due to atrophy, hypoplasia or agenesis. This term is intended to be used in situations where it is not known if thinning of the corpus callosum (for instance, as visualized by magnetic resonance tomography) is due to abnormal development (e.g. a leukodystrophy) or atrophy following normal development (e.g. neurodegeneration). Evidence: PCS. Frequency: 1/1. (PMID:30985297)
- Hypomimic face (HP:0000338): A reduced degree of motion of the muscles beneath the skin of the face, often associated with reduced facial crease formation. Evidence: PCS. Frequency: 1/2. (PMID:26467484)
- 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: 2/2. (PMID:26467484)
- Neonatal onset (HP:0003623): Onset of signs or symptoms of disease within the first 28 days of life. Evidence: PCS. Frequency: 1/1. (PMID:30985297)
- Hyporeflexia (HP:0001265): Reduction of neurologic reflexes such as the knee-jerk reaction. Evidence: PCS. Frequency: 2/2. (PMID:26467484)
- Cerebral atrophy (HP:0002059): Atrophy (wasting, decrease in size of cells or tissue) affecting the cerebrum. Evidence: PCS. Frequency: 3/3. (PMID:26467484;PMID:30985297)
- 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: PCS. (PMID:15746149)
- 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: PCS. Frequency: 2/2. (PMID:26467484)
- 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: PCS. Frequency: 1/2. (PMID:26467484)
- Gait disturbance (HP:0001288): The term gait disturbance can refer to any disruption of the ability to walk. Evidence: PCS. Frequency: 1/2. (PMID:26467484)
- Hypoplasia of the corpus callosum (HP:0002079): Underdevelopment of the corpus callosum. Evidence: PCS. Frequency: 1/2. (PMID:26467484)
- 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: 2/2. (PMID:26467484)
- X-linked recessive inheritance (HP:0001419): A mode of inheritance that is observed for recessive traits related to a gene encoded on the X chromosome. In the context of medical genetics, X-linked recessive disorders manifest in males (who have one copy of the X chromosome and are thus hemizygotes), but generally not in female heterozygotes who have one mutant and one normal allele. Evidence: PCS. (PMID:26467484)
- Drooling (HP:0002307): Habitual flow of saliva out of the mouth. Evidence: PCS. Frequency: 1/2. (PMID:26467484)
- Falls (HP:0002527). Evidence: PCS. Frequency: 1/2. (PMID:26467484)
- 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: PCS. Frequency: 1/1. (PMID:30985297)
These phenotypes are associated with the disease syndromic X-linked intellectual disability Hedera type (OMIM:300423).