We describe a twentieth month old infant who had a pycnodysostosis syndrome. This malformation shows a loss of the normal mandible angle with generalized bone hyperdensification. The first produced and airway obstruction, with special relevance during sleeping hours. A polysomnography revealed an obstructive sleep apnea syndrome. The respiratory picture deteriorated with worsening of the airway obstruction, hypoxemia and finally pulmonary hypertension and cor pulmonale. A tracheostomy was performed, with resolution of the sleep apnea and pulmonary hypertension. The etiology, pathophysiologic consequences and surgical treatment of obstructive sleep apnea syndrome is reviewed.