Mental Retardation, Autosomal Recessive 5

Alternative Names

  • MRT5
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WHO-ICD-10 version:2010

Mental and behavioural disorders

Mental retardation

OMIM Number

611091

Mode of Inheritance

Autosomal recessive

Gene Map Locus

5p15.31

Description

MRT5 is a neurodevelopmental disorder encompassing, in addition to delayed speech and psychomotor development, a number of dysmorphic features such as microcephaly, long and narrow face, bushy eyebrows with synophrys, hypotelorism, large nose with long columella, short philtrum, and full upper lip. Many affected individuals have short stature, and some have later onset of muscular hypertonia and spasticity.

Diagnosis is made upon observing the aforementioned symptoms. Some patients can benefit from specific programs aimed at people with developmental disabilities to help them learn basic life skills.

Molecular Genetics

MRT5 was mapped to chromosome 5p15, consequently causative mutations in the NSUN2 gene were uncovered. The latter gene encodes a conserved RNA methyltransferase, and this indicates to the role of RNA methylation in higher cognitive functions. So mutations in the NSUN2 gene leading to total lack of the NSUN2 protein or to a truncated version of it cause MRT5. The NSUN2 protein also interacts with the mitotic spindle and plays an important role in cell division. This connection between NSUN2 mutations and MRT5 highlights both the role of cell proliferation genes in normal brain development and link between abnormal cell cycle and microcephaly phenotypes.

Epidemiology in the Arab World

View Map
Subject IDCountrySexFamily HistoryParental ConsanguinityHPO TermsVariantZygosityMode of InheritanceReferenceRemarks
611091.1.1United Arab EmiratesMaleNoYes Neurodevelopmental delay; Cerebellar at...NM_017755.6:c.1020delHomozygousAutosomal, RecessiveKomara et al. 2015
611091.2.1LebanonMaleYesYes Seizure; Intellectual disability; ...NM_017755.6:c.538-1G>CHomozygousAutosomal, RecessiveMartinez et al. 2012 The novel mutation d...
611091.2.2LebanonFemaleYesYes Intellectual disability; Axial hypotoni...NM_017755.6:c.538-1G>CHomozygousAutosomal, RecessiveMartinez et al. 2012
611091.2.3LebanonFemaleYesYes Intellectual disability; Axial hypotoni...NM_017755.6:c.538-1G>CHomozygousAutosomal, RecessiveMartinez et al. 2012
611091.3Saudi ArabiaMaleNoYes Trigonocephaly; Hypotelorism; Wide mouth...NM_017755.6:c.1478delHomozygousAutosomal, RecessiveShaheen et al. 2019

Other Reports

United Arab Emirates

Al-Gazali et al. 1999 reported on a patient from an inbred UAE family of Baluchi origin with microcephaly, arched eyebrows, prominent eyes, prominent nasal bridge, smooth philtrum, and thin upper lip vermilion. The patient exhibited severe spasticity and developed convlusions at half year of age. History of similarly affected brother with microcephaly and severe intellectual disability. 

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