ESPE Abstracts

Background/Aims: Schaaf-Yang syndrome (SYS) is a rare disorder caused by a truncating mutation in the gene MAGEL2, located in the Prader-Willi critical region on chromosome 15. SYS is characterized as a Prader-Willi-like (PWL) disorder, with neonatal hypotonia, feeding problems in early infancy and intellectual disability, obesity and behavioral problems throughout childhood. In this case report we describe a 15-year-old girl, receiving GH treatment since age 6 because of partial GH deficiency. She was diagnosed with SYS at 12 years of age.

Methods: Medical records were retrospectively reviewed. Data on height, weight and BMI were available for the entire eight years of GH treatment. Data on body composition were only available for the most recent four years since she was diagnosed with SYS.

Results: The patient was extensively evaluated by the Dept. of Clinical Genetics and Pediatric Neurology, because of psychomotor delay. Whole exome sequencing (WES) eventually showed a frameshift, de novo mutation in the MAGEL2 gene. After 8 years of GH treatment, height SDS had increased from -3.95 to -1.11. BMI improved from +1.53 SDS to -0.09 SDS. After being diagnosed with SYS, she received multidisciplinary care by the Dutch PWS team. In these 4 years, fat mass percentage (fat%) improved from 44% to 31.2%, a decrease of 1.21 SDS and lean body mass (LBM) increased from -2.96 SDS to -2.06 SDS.

Conclusion: This patient with SYS shows a normalization of height SDS, a significant decrease in fat% SDS and increase of LBM SDS during 8 years of GH treatment. Further studies need to confirm the effectiveness of GH treatment in patients with SYS.