Prader-Willi Syndrome (PWS) is a rare and complex genetic condition affecting roughly 400,000 people worldwide. PWS is non-inherited, and linked to the deletion or incompleteness of genes on the 15th chromosomes. This chromosomal abnormality leads to neurological changes which cause altered growth patterns and development with associated cognitive disability and obsessive eating patters (hyperphagia).
When recognised at birth a child with PWS will usually present as floppy, have poor muscle tone (hypotonia) and have a weakened sucking reflex, which often leads to poor feeding and failure to thrive. Babies may have a weak cry, often respond poorly to stimulation and can seem tired/have difficulty waking. Lack of eye coordination, such as abnormal alignment (strabismus) or eyes turning towards one side may be present, along with some known facial features including almond shaped eyes, narrowing of the of the head toward the temples and a narrow top lip with turned down mouth.
Meeting of developmental milestones is delayed in most aspects, such as sitting, crawling, walking and talking later than other children. Intellectual disability is present in varying degrees in most cases. Underdeveloped sex organs including undescended testes may be present in males, and both males and females may produce little or no sex hormones resulting in incomplete development at puberty and in most cases infertility.
Classically known symptoms present from early childhood, which stay throughout life, include a constant pre-occupation with food and constant craving and seeking of food. In the brain, the hypothalamus (part of the brain which controls hunger) is affected in people with PWS. This leads to a strong psychological drive to eat, as normal satiety (feeling of fullness) does not exist. This drive to eat results in dangerous behaviours such as eating large quantities of food, food seeking behaviours (eg stealing, hoarding, eating from the garbage), and has potential for rapid weight gain and obesity if not carefully managed.
Behavioural problems may develop including psychological conditions, controlling and manipulative behaviour as well as obsessive-compulsive and repetitive behaviours. Children and adults with PWS may have angry outbursts, particularly when denied food or when unable to handle changes to regular routine. Emotions and behaviour are often erratic and can be very challenging.