ESPE Abstracts

Context: Infants and toddlers with Prader-Willi Syndrome (PWS) have a mental and motor developmental delay. Short-term data suggest a positive effect of growth hormone (GH) on mental and motor development in infants and children with PWS. There are, however, no longer-term results about the effects of GH treatment on mental and motor development.

Objective: To investigate the longer-term effects of GH on psychomotor development in infants and toddlers with PWS and the effect of age at start of GH treatment on psychomotor development.

Methods: Prospective cohort study in 63 young children with PWS. All patients were naïve to GH treatment at time of enrolment and started GH in a dose of 1 mg/m²/day (≈0.035 mg/kg/day). Main outcome measures were mental and motor developmental age assessed with Bayleys Scales of Infant Development II (BSID-II) and expressed as % of the expected development (100%).

Results: Thirthy-five boys and 28 girls participated in the evaluation of psychomotor development. GH treatment was started at a median (IQR) age of 1.0 year (0.7-1.6). During 3 years of GH, mean (SEM) mental development increased from 58.1% (2.8) at baseline to 79.6% (3.7), and motor development from 41.9% (2.9) to 78.2% (3.9; both P<0.01). In spite of this improvement, the average mental and motor development after 3 years of GH was still significantly lower compared to healthy references (both P<0.001). A lower baseline psychomotor development and a younger age at start of GH treatment were associated with a higher increase in mental and motor development (all P<0.01).

Conclusion: Mental and motor development increased significantly during 3 years of GH treatment, reducing the gap between infants with PWS and healthy peers. Infants with a lower baseline psychomotor development advanced more than infants with a higher baseline psychomotor development. Currently, the increased awareness of PWS and the improved genetic tests have made it possible to diagnose PWS during early infancy. As starting GH treatment at a younger age results in a better psychomotor development, we nowadays start GH treatment in very young infants with PWS.