Maladaptive behaviors and cognitive impairment can be main problems in patients with Prader-Willi Syndrome. Understanding difficulties underlying the maladaptive behavior through early diagnosis and management allow tremendous improvement in the whole clinical picture.

To study the psychobehavioral deviations in a sample of Egyptian children with Prader-Willi syndrome and possible relation to genotype.

We included 15 out of 72 patients of both sexes, aged from 5–15 years old from the National Research Centre. All patient were fulfilling the diagnostic threshold of modified list of Prader-Willi criteria. Detailed cytogenetic analysis was done using: conventional cytogenetic analysis of peripheral blood lymphocytes and Fluorescent in Situ Hybridization. Cognitive and psychological profile of Patients were assessed using

1. (a) standard and semi structured psychiatric sheet and interview

2. (b) Wechsler Intelligence Scale for Children,

3. (c) Child Behavior Checklist for ages 4–18years,

4. (d) Conner’s’ Parent Rating Scale-Revised; long version,

5. (e) Childhood Autism Rating Scale.

66.7 % of the patients were deletion positive and 33.3% were negative. 100% of the sample were mentally subnormal. 26.3% had autistic symptoms ranging from features to severe form, all were deletion negative. High prevalence of inattention, hyperactivity, anxiety, social, cognitive and behavioral problems were evident in the patients, manifested in more frequency and severity in non-deletion patients.

Cognitive and psychological challenges were evident in PWS patients’. There were some clinical differences according to different genotypes.