- Hyporeflexia (HP:0001265): Reduction of neurologic reflexes such as the knee-jerk reaction. Evidence: TAS. Frequency: Occasional (HP:0040283). (OMIM:613402)
- Progressive microcephaly (HP:0000253): Progressive microcephaly is diagnosed when the head circumference falls progressively behind age- and gender-dependent norms. Evidence: PCS. (PMID:23224214)
- Skeletal muscle atrophy (HP:0003202): The presence of skeletal muscular atrophy (which is also known as amyotrophy). Evidence: TAS. (OMIM:613402)
- Microcephaly (HP:0000252): Head circumference below 2 standard deviations below the mean for age and gender. Evidence: PCS. Frequency: 13/13. (PMID:20118933;PMID:23224214)
- Hypoplasia of the corpus callosum (HP:0002079): Underdevelopment of the corpus callosum. Evidence: PCS. (PMID:20118933)
- 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: 11/11. Onset: Infantile onset (HP:0003593). (PMID:20118933)
- 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: 2/2. (PMID:23224214)
- 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: PCS. Onset: Juvenile onset (HP:0003621). (PMID:23224214)
- 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: 13/13. (PMID:20118933;PMID:23224214)
- 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: 2/2. (PMID:23224214)
- Motor delay (HP:0001270): A type of Developmental delay characterized by a delay in acquiring motor skills. Evidence: PCS. (PMID:23224214)
- 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: PCS. (PMID:20118933)
- Autosomal recessive inheritance (HP:0000007): 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 individuals with two pathogenic alleles, either homozygotes (two copies of the same mutant allele) or compound heterozygotes (whereby each copy of a gene has a distinct mutant allele). Evidence: PCS. (PMID:20118933)
- Ventriculomegaly (HP:0002119): An increase in size of the ventricular system of the brain. Evidence: PCS. Frequency: 6/6. (PMID:20118933)
- Hyperactivity (HP:0000752): Hyperactivity is a condition characterized by constant and unusually high levels of activity, even in situations where it is deemed inappropriate. Evidence: PCS. Frequency: 12/12. (PMID:20118933;PMID:23224214)
- Simplified gyral pattern (HP:0009879): An abnormality of the cerebral cortex with fewer gyri but with normal cortical thickness. This pattern is usually often associated with congenital microcephaly. Evidence: TAS. (OMIM:613402)
These phenotypes are associated with the disease microcephaly, seizures, and developmental delay (OMIM:613402).