Genetic testing: expansion of CGG repeat on FMR1 gene on chr. X.
55-200 repeats = premutation range, associated with tremor/ataxia syndrome and premature ovarian failure
>200 repeats = Fragile X syndrome
Findings on investigations:
MRI: T2 white matter hyperintensities in the middle cerebellar peduncles or brain stem. Cereberal white matter hyperintensities and atrophy may occur.
In white matter enlarged astrocytes with inclusions. Inclusion bodies in neurons and astrocytes occur in the CNS and in autonomic neurons.