HIVEP2-related intellectual disability
HIVEP2-related intellectual disability is a rare neurological disorder caused by mutations in the HIVEP2 gene, characterized by moderate to severe developmental delay, intellectual disability, and mild physical abnormalities.
Overview
HIVEP2-related intellectual disability is a neurological disorder characterized by moderate to severe developmental delay and intellectual disability, along with mild physical abnormalities (dysmorphic features). This condition is rare, with at least nine individuals described in the medical literature.
Symptoms
Early symptoms of the condition include weak muscle tone (hypotonia) and delayed development of motor skills, such as sitting, standing, and walking. After learning to walk, many affected individuals continue to have difficulty with this activity; their walking style (gait) is often unbalanced and wide-based. Speech is also delayed, and some people with this condition never learn to talk.
Most people with HIVEP2-related intellectual disability exhibit neurodevelopmental disorders, which may include:
- Hyperactivity
- Attention deficit disorder
- Aggression
- Anxiety
- Autism spectrum disorder, a group of developmental disorders characterized by impaired communication and social interaction
Other features of the condition include mild abnormalities in the structure of the brain and an abnormally small brain and head size (microcephaly). Less common health problems include:
- Seizures
- Recurrent ear infections
- Eye disorders, such as eyes that do not look in the same direction (strabismus), "lazy eye" (amblyopia), and farsightedness (hyperopia)
- Gastrointestinal problems, which can include backflow of acidic stomach contents into the esophagus (gastroesophageal reflux) and constipation
Many people with the condition also have unusual physical features, such as widely spaced eyes, although there is no characteristic pattern of such features among affected individuals.
Causes & Risk Factors
HIVEP2-related intellectual disability is caused by mutations in the HIVEP2 gene. The protein produced from this gene is most abundant in the brain, where it controls the activity (expression) of genes involved in brain growth and development.
Mutations in the HIVEP2 gene are thought to lead to a shortage of functional HIVEP2 protein. It is unclear how these genetic changes result in the features associated with the condition, although researchers speculate that a shortage of the HIVEP2 protein alters the expression of several genes involved in brain growth and development. Abnormalities in the growth and development of the brain likely underlie the cognitive problems and other neurological features of HIVEP2-related intellectual disability. It is unclear how HIVEP2 gene mutations contribute to the unusual physical features and health problems that can occur with this condition.
Inheritance
This condition is inherited in an autosomal dominant pattern, which means one copy of the altered gene in each cell is sufficient to cause the disorder.
Most cases of this condition result from new (de novo) mutations in the gene that occur during the formation of reproductive cells (eggs or sperm) in an affected individual’s parent or in early embryonic development. These cases occur in people with no history of the disorder in their family.
Other Names
- Mental retardation, autosomal dominant 43
- MRD43