Autism spectrum disorders in Prader-Willi and Angelman syndromes: a systematic review.

Autism spectrum disorders (ASDs) have been linked with maternally derived duplications/triplications of chromosome 15q11-13 and therefore might occur more frequently in people with Prader-Willi syndrome (PWS) when due to uniparental disomy (UPD), than in other forms of chromosomal abnormality involving this region [i.e. deletion (DEL) forms of PWS and DEL+UPD forms of Angelman's syndrome -(AS)]. Twelve studies regarding ASD in PWS and AS were reviewed. It was noteworthy that among the genetically confirmed UPD and DEL cases of PWS and AS, the rate of ASD was 25.3% (38/150; range 0-36.5%) in PWS and 1.9% in AS (2/104; range 0-100%) (Fisher's exact P<0.0001). Among the subset of cases with confirmed UPD or DEL, the rate of ASD in the UPD cases of PWS was significantly higher (20/53) than in the remaining combined samples (i.e. DEL PWS+UPD AS+DEL AS cases; 20/201) (Fisher's exact P<0.0001). ASD in UPD PWS cases (20/53) compared with DEL PWS cases (18/97) was also statistically significant (Fisher's exact P=0.0176). Thus, the limited available evidence supported the prediction that overexpression of maternally imprinted genes in 15q11-13 confers a risk for ASD. Further research will be required to confirm these findings.