Furthermore, the autistic-like behaviours and dementia-like stages can be phenotypically dissociated in terms of behavioural patterns (hyperactivity vs hypoactivity; normal learning vs cognitive impairment, etc.)and dopaminergic status (increased TH+ cells vs decreased TH+ cells; increased TH striatal expression vs decreased TH expression, etc.)suggesting that parallel disease mechanisms might concurrently lead to autistic-like and dementia-like symptoms in MPS-IIIA. The gene discussed is TH; the disease is mucopolysaccharidosis type 3A.