Mental Retardation, AD 53
Patient Information
Characteristics
Background and History
This is one of a large number of mental retardation disorders in which a gene change (mutation) is responsible. The mutation leads to widespread neurological dysfunction.
Clinical Correlations
Poor muscle tone is evident early leading to the ‘floppy baby’ designation. Developmental milestones are delayed and many children never learn to walk or speak. Intellectual disabilities range from mild to severe. Seizures occur in many infants and children. Breathing problems, feeding difficulties and slow physical growth are frequently present. Behavioral features including anxiety, hyperactivity, aggression, and signs of autism have been reported.
The lid openings slant downward and the upper lids have a prominent extra fold (epicanthal fold). Visual impairment with poor visual tracking may be present.
The MRI scan of the brain may be normal.
Genetics
Inheritance
A gene change (mutation) has been identified in this condition. The neurologic impairment prevents reproduction but the nature of the mutation suggests that an autosomal dominant inheritance pattern would be expected.
Pedigree
Autosomal dominant
Autosomal dominant disorders require only one mutation for the disease to be expressed. Since an affected parent has two chromosomes, only one of which has the mutant gene, parents can expect that half (50%) of their children will receive that one and inherit the disease. It is common for individuals that inherit the mutation, however, to not have evidence of the disease (nonpenetrance).
Autosomal dominant inheritance leads to a vertical pattern of transmission
Diagnosis and Prognosis
There are no physical or neurologic signs specific to this disorder and a gene study is necessary to the diagnosis. Pediatricians and neurologists are likely to collaborate in the evaluation and care of these patients. No treatment has been reported and nothing is known regarding longevity.
An EEG (electroencephalogram) and a brain MRI may be used but the findings are not specific to this condition.
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