UNDERSTANDING THE EATING DISORDER AFFECTING PEOPLE WITH PRADER-WILLI-SYNDROME

The propensity to severe over-eating, which may lead to life-threateni ng obesity, is characteristic of people born with the Prader Willi Syn drome (PWS). This syndrome is caused by the loss of expression of eith er a specific or a few specific genes on chromosome 15 at q11-13. In t he case of PWS this is due to a deletion affecting chromosome 15 of pa ternal origin and the fact that specific genes at the same locus, but on chromosome 15 of maternal origin, are imprinted and therefore not e xpressed. The characteristic tendency to over-eat is observed from ear ly childhood and, particularly in later life, can lead to severe obesi ty if unsupervised access to food is allowed. The normal satiety respo nse to the intake of calories appears both impaired and delayed and th erefore eating continues. The pathophysiology, which underpins this ab normal eating behaviour, is likely to relate to the functioning of spe cific hypothalamic nuclei. PWS is an example of what has been called a 'behavioural phenotype'. The research task is to link the observed ge netic abnormalities to brain function and in turn to the eating behavi our. This paper examines these links and proposes a conceptual model t o help in the understanding and management of the excessive eating beh aviour.