 Although Tourette syndrome is the most common cause of tic disorders, other sporadic, genetic, and neurodegenerative disorders may also exhibit tics.Conditions that may manifest tics or stereotyped movements include developmental disorders; autism spectrum disorders and stereotypic movement disorder; Sydenham's chorea; idiopathic dystonia; and genetic conditions such as Huntington's disease, neuroacanthocytosis, pantothenate kinase-associated neurodegeneration, Duchenne muscular dystrophy, Wilson's disease, and tuberous sclerosis.Other possibilities include chromosomal disorders such as Down syndrome, Klinefelter syndrome, XYY syndrome and fragile X syndrome.