Asperger syndrome associated with Steinert's myotonic dystrophy.

Steinert's myotonic dystrophy was diagnosed in a 10-year-old girl with Asperger syndrome. This form of myotonic dystrophy is one of a growing list of genetic diseases that can be diagnosed by analysis of a gene with trinucleotide repeats that may expand. The patient has the largest such expansion known within her pedigree. She has many of the psychological deficits that have been reported in adult-onset myotonic dystrophy. This is the first known report of an association of this disorder with Asperger syndrome. Recently Moebius syndrome has been found in association with disorders of the autistic spectrum; physicians practicing developmental medicine should now also consider Steinert's myotonic dystrophy when evaluating children with facial diplegia.