Obstructive Sleep Apnea in Patients with MPS: Need for Anatomic Evaluation of the Airway

The mucopolysaccharidoses are a group of inherited, progressive disorders caused by mutations in the genes coding for lysosomal enzymes required to break down glycosaminoglycans (GAGs). GAGs are long-chain complex carbohydrates that are key components to the ground substance of connective tissue, nuclear, and cell membranes. This leads to a multitude of signs and symptoms that worsen with age. Respiratory involvement is common, and is usually manifested by recurrent respiratory infections, upper and lower airway obstruction, restrictive lung disease, sleep disordered breathing (SDB) and exertional dyspnea. The presence of obstructive sleep apnea (OSA) not easily amenable to non-invasive positive pressure ventilation (NIPPV) should prompt one to perform an airway evaluation to look for external compression versus intrinsic malacia of the airways, as their management is different. We describe two cases that illustrate differences in evaluation depending on mechanism of their airway obstruction. The first patient with Morquio A syndrome (MPS IVA) and OSA was found to have compression of his trachea by his innominate artery and thyroid gland requiring surgical management. The second patient with Hunter’s syndrome (MPS II) and OSA were found to have intrinsic malacia of the airways requiring only bilevel positive pressure ventilation (BiPAP).