Fragile X Syndrome | Landau-Kleffner Syndrome (Acquired Epileptic Aphasia) | Tuberous Sclerosis Complex | Multiple Complex Developmental Disorder
The cause of fragile X syndrome is a mutation in FMR1 (including
the occurrence of a greatly expanded trinucleotide repeat) at Xq27.3.
The diagnosis is now easily made using Southern blotting and polymerase
chain reaction testing of persons suspected of having the syndrome.
Studies indicate that approximately 3%–5% of
persons diagnosed as autistic have the FMR1 mutation
(Farzin et al. 2006; Fombonne et al. 1997; Wassink et al. 2001). While small, this prevalence rate is sufficient
to warrant testing of all autistic persons for the mutation, if
only because of the implication for family genetic counseling. Study
of persons who have fragile X syndrome has revealed social and communicative
handicaps that resemble the symptoms of autism (Loesch et al. 2007; Rogers et al. 2001). FMR1 is known
to play a role in many neurodevelopmental processes, and some of
these may involve systems that are defective in autism (Feinstein and Reiss 1998).