Adaptive skills, cognitive, and behavioral characteristics of Costello syndrome

Costello syndrome is a rare congenital disorder whose diagnosis is based on clinical findings. The underlying genetic cause has not been identified. Common characteristics include failure to thrive, feeding problems, short stature, coarsening of facial features, developmental delay, mental retardation, skeletal problems, cardiac complications, and increased risk for solid tumors. Given its rarity, existing literature is limited regarding its natural course. Developmental milestones and intellectual functioning have never been systematically studied in this population, therefore this study focused on defining developmental and intellectual attributes. Data was obtained through solicited participation at the 3rd International Costello Syndrome Meeting. A total of 18 children (age 3-20 years) were administered the Leiter-R brief-IQ and the Peabody picture vocabulary test (PPVT)-III to assess nonverbal cognitive functioning and receptive vocabulary. Parents/guardians completed the child behavior checklist (CBCL) and participated in an interview process to complete the survey form of the Vineland adaptive behavior scales to assess emotional/behavioral issues and adaptive behavior. Results indicated that nonverbal cognitive functioning ranged from 1.5 to 4.3 SD below the age mean. Receptive vocabulary skills ranged from average functioning to 4 SD below the age mean. Adaptive behavior composites were all in the low range (2.0 to >5.0 SD below age mean), however there was significant variability in the range of domain scores. CBCL results ranged from normal to clinically significant across various clinical parameters. These data support a generalized descriptive pattern of developmental delay and mental retardation, with noted variability in receptive language, level of adaptive behavior functioning, and emotional/behavioral aspects. Skills and behavior are compared to existing literature of children with various syndromes.