Resolution of obstructive sleep apnea in Hurler syndrome after bone marrow transplantation

Hurler syndrome, a lethal inborn error of lysosomal metabolism, results from the systemic accumulation of glycosaminoglycan. The progressive deposition of glycosaminoglycan in tissues of the upper aerodigestive tract has been suspected as the cause of airway obstruction, and many children have required tracheostomy. In a 3-year-old patient with Hurler syndrome, polysomnography confirmed the clinical impression of obstructive sleep apnea. Biopsy of an enlarged tonsil demonstrated that more than half the tissue volume resulted from abnormal lysosomal inclusions in macrophages. Three months after transplantation, repeat testing demonstrated resolution of airway obstruction, and 6 months after transplantation, tonsil biopsy showed complete absence of lysosomal inclusions. Bone marrow transplantation produces effective metabolic correction for Hurler syndrome and may be life-saving for patients with obstructive apnea.