[Effects of hypocaloric diet on respiratory manifestations in Willi-Prader syndrome]

Prader-Willi syndrome (PWS) is a multisystem disorder with hyperphagia and obesity. Breathing disorders such as snoring, sleep apnea syndrome, and sleep hypoventilation have also been reported.

Jonathan was born with the typical features of PWS. He developed exercise dyspnea, cyanosis and nocturnal sweating at the age of 3 years. A few months later, a respiratory failure required his admission to the intensive care unit. His weight was then 48 kg (300% ideal body weight (IBW); physical examination showed polypnea (60 breaths/min), cyanosis, fat deposition on the chest wall. Transcutaneous oxygen saturation was 65%, carbon dioxide tension 81 mmHg (capillary sample). Pulmonary hypertension was found (mean arterial pulmonary pressure = 55 mmHg). Polysomnography detected hypoventilation with persistent hypoxemia increasing during the night and transient dips of oxygen saturation with bradycardia. He was treated with oxygen, mechanical ventilation (facial mask) and a low caloric diet (600 cal/day). Four months later, he weighed 33 kg (200% IBW); the respiratory features had resolved and gazometric values and pulmonary pressure returned to the normal ranges. Polysomnography showed only obstruction apnea and hypopnea without oxygen desaturation.

Patients with PWS may develop respiratory symptoms sufficient by severity to be life threatening. They are related to morbid obesity and are influenced by a hypocaloric diet. Follow-up of patients with this syndrome must include repeated respiratory evaluation.