Noonan syndrome: an update on growth and development.

Abstract

To provide an update on recent developments on Noonan syndrome with a special focus on endocrinology, bone, and metabolism aspects. The key issues still to be resolved and the future therapeutic perspectives will be discussed. The discovery of the molecular genetic causes of Noonan syndrome and Noonan-syndrome-related disorders has permitted us to better understand the mechanisms underlying the different symptoms of these diseases and to establish genotype-phenotype correlations (in growth patterns for example). In addition to the classical clinical hallmarks of Noonan syndrome, new important aspects include decreased fertility in men, lean phenotype with increased energy expenditure and possible impact on carbohydrate metabolism/insulin sensitivity, and impaired bone health. Further clinical studies are needed to investigate the long-term impact of these findings and their possible interconnections. Finally, the understanding of the crucial role of RAS/mitogen-activated protein kinases dysregulation in the pathophysiology of Noonan syndrome allows us to devise new therapeutic approaches. Some agents are currently undergoing clinical trials in Noonan syndrome patients. On the last 10 years, our knowledge of the molecular basis and the pathophysiology of Noonan syndrome has greatly advanced allowing us to gain insight in all the aspects of this disease and to devise new specific therapeutic strategies.