Abstract
Smith-Magenis syndrome (SMS) is a rare genetic neurodevelopmental disorder characterised by behavioural disturbances, intellectual disability and early onset obesity. The physical features of this syndrome are well characterised; however, behavioural features, such as sleep disturbance, are less well understood and difficult to manage. Sleep issues in SMS are likely due to a combination of disturbed melatonin cycle, facial anatomy and obesity-related ventilatory problems. Sleep disorders can be very distressing to patients and their families, as exemplified by our patient's experience, and can worsen behavioural issues as well as general health. This case demonstrates the successful use of non-invasive ventilation in treating underlying obesity hypoventilation syndrome and obstructive sleep apnoea. As a consequence of addressing abnormalities in sleep patterns, some behavioural problems improved.