• autism
• mental retardation
• subtelomeric deletions
• duplication 15q11-13

• PPAR, peroxisome proliferator activated receptor
• PPRE, PPAR response elements
• BMI, body mass index
• HDL, high density lipoprotein
• LDL, low density lipoprotein
• AT, ataxia-telangiectasia
• LOH, loss of heterozygosity
• PWS, Prader-Willi syndrome
• NARP, neuropathy ataxia and retinitis pigmentosa
• BFNC, benign familial neonatal convulsions
• BFIC, benign familial infantile convulsions

Autism is a chronic and severe neuropsychiatric disorder with an early onset, characterised by qualitative impairments of social interaction, deviant development of language and other communicative skills, delayed cognitive development, and restricted repetitive and stereotyped interests and behaviours.^1,2 The prevalence in the general population was estimated at 5.5/10 000 but more recent investigations report higher rates.³ Males are affected more often than females, with a predominance of 3 to 1.⁴ Mental retardation is present in about 75 to 85% of patients with autism,^1,5,6 and almost half of all autistic patients are functionally mute.⁵

The causes and mechanisms underlying autism are heterogeneous, varying from genetic causes, that is, chromosome abnormalities and conditions with Mendelian inheritance such as metabolic disturbances, to infectious causes and teratogenic influences.^7–9 The prevailing view is that autism is caused by a pathophysiological process arising from the interaction of an early environmental insult and a genetic predisposition.¹⁰ However, the aetiology often remains obscure and earlier studies reported that causal medical conditions were detectable in a relatively small percentage of autistic patients.^11,12 There is increasing evidence that genetic factors may well play a major role in the remaining idiopathic cases.¹³ In support of this hypothesis is the recent identification of deletions in the short arm of the X chromosome,¹⁴ duplications of the Prader-Willi/Angelman critical region on chromosome 15q,^15,16 linkage to 7q31 and 2q,^17,18 as well as the high monozygotic twin concordance rates,^19,20 and high recurrence risk among sibs of patients with idiopathic autism.²¹

Autism poses an extremely heavy burden for affected subjects, their families, and society. Research focusing on biological causes and on guidelines for these studies in each specific person is important, both in diagnostics, management, …