Mental Retardation, Autosomal Recessive 36 (mrt36)

What is Mental Retardation, Autosomal Recessive 36 (mrt36)?

Also known as Intellectual Disability-Strabismus syndrome, this rare genetic syndrome presents with intellectual disability and esotropia (which causes both eyes to turn inward).

Mental retardation is now generally referred to as intellectual disability (intellectual developmental disorder).

This syndrome is also known as:
Intellectual disability - esotropia - ADAT3 mutations

What gene changes cause Mental Retardation, Autosomal Recessive 36?

Changes in the ADAT3 gene are responsible for causing the syndrome.

It is inherited in an autosomal recessive pattern.

What are the main symptoms of Mental Retardation, Autosomal Recessive 36?

Among the main symptoms of the syndrome is moderate to severe intellectual disability. This is also accompanied by behavioral issues, including hyperactivity and aggression.

Esotropia (inward facing eyes) is a main symptom of the syndrome. Other facial and physical features include a small head as well as low muscle tone and a stiffness of the muscles (spasticity). Individuals generally have delayed and restricted growth and are underweight with a short stature.

Some affected individuals also present with cysts and atrophy of parts of the brain.

Possible clinical traits/features:
Autosomal recessive inheritance, Infantile onset, Microcephaly, Failure to thrive, Esotropia, Muscular hypotonia, Intellectual disability

How does someone get tested for Mental Retardation, Autosomal Recessive 36?

The initial testing for Mental Retardation, Autosomal Recessive 36 (mrt36), with or without seizures, can begin with facial analysis screening, through the FDNA Telehealth telegenetics platform, which can identify the key markers of the syndrome and outline the need for further testing. A consultation with a genetic counselor and then a geneticist will follow.

Based on this clinical consultation with a geneticist, the different options for genetic testing will be shared and consent will be sought for further testing.

Medical information on Mental Retardation, Autosomal Recessive 36 (mrt36)

Eight consanguineous families with the main clinical features being intellectual disability and strabismus underwent exome sequencing (Alazami et al., 2013) and mutations were found in the ADAT3 gene encoding adenosine deaminase that acts on transfer RNA. Other features, spasticity, seizures, rocephaly only occurred in a few.
El-Hattab et al. (2016) described additional 15 individuals from 11 families who are homozygous for the same founder mutation as the patients described by Alazami et al. (2013). In addition to intellectual disability and strabismus, the majority of the patients showed microcephaly and growth failure. Additional features reported included dysmorphic features (prominent forehead, upslanted palpebral fissures, epicanthus, depressed nasal bridge; overhanging columella), behavioral problems, recurrent otitis media, and growth hormone deficiency. Brain imaging findings were nonspecific.

* This information is courtesy of the L M D.
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