LEP and obesity due to melanocortin 4 receptor deficiency: Obesity is a risk factor for OSAS because (i) it induces enlargement of structures surrounding the airway, contributing to upper airway narrowing; (ii) an excess of fat deposition is also observed under the mandible and in the tongue, soft palate and uvula; (iii) lung volumes are reduced in obese patients, further decreasing longitudinal tracheal traction forces and pharyngeal wall tension thus leading to the narrowing of the airway; (iv) obesity-related increase in leptin and leptin resistance might contribute itself to the genesis of OSAS (20, 21).