Comparative analysis of autistic traits and behavioral disorders in Prader-Willi syndrome and Asperger disorder.

Prader-Willi syndrome (PWS) is a neuro-genetic disorder caused by the absence/loss of expression of one or more paternally expressed genes on chromosome 15 (q11-13). In this study, a comparative analysis of intelligence level and autistic traits was conducted between children with PWS (n = 30; 18 males, 12 females; age = 10.6 ± 2.8 years) and those with Asperger disorder (AD; n = 31; 24 males, 7 females; age = 10.5 ± 3.1 years). The children were compared by age group: lower elementary school age (6-8 years), upper elementary school age (9-12 years), and middle school age (13-15 years). As results, the intelligence levels of children with PWS were significantly lower than those with AD across all age groups. Autistic traits, assessed using the Pervasive Developmental Disorders Autism Society Japan Rating Scale (PARS), revealed that among elementary school age children, those with PWS had less prominent autistic traits than those with AD, however, among middle school age children, those with PWS and AD showed similar prominence. An analysis of the PARS subscale scores by age group showed that while the profiles of autistic traits for children with PWS differed from those of children with AD at elementary school age, the profiles showed no significant differences between the groups at middle school age. The findings suggest that autistic traits in PWS become gradually more prominent with increasing of age and that these autistic traits differ in their fundamental nature from those observed in AD.