Sleep abnormalities in untreated patients with mucopolysaccharidosis type VI

Mucopolysaccharidosis type VI (MPS VI) is a lysosomal storage disease that affects an enzyme responsible for the degradation of glycosaminoglycans (GAGs). Partially degraded GAGs accumulate in several tissues, such as the upper airways (UA), which leads to the development of obstructive sleep apnea (OSA). Our objective was to determine the prevalence of OSA in a group of untreated patients with MPS VI and the association of OSA with clinical and echocardiographic findings. Patients aged 4 years or older with a biochemical diagnosis of MPS VI were included. Data about clinical history, physical examination, Doppler echocardiogram, and overnight polysomnography (PSG) were collected. Our results showed that of the 28 participants, 14 were boys; mean age was 98.5 months, and mean age at MPS VI diagnosis was 48.4 months. Snoring, witnessed apnea, pectus carinatum, and macroglossia were the main clinical findings. PSG results showed that 23:27 patients (85.1%) had OSA which was mild in 4, moderate in 5, and severe in 14 patients. Echocardiograms showed evidence of pulmonary hypertension (PH) in 14 patients. Lower (P = 0.037) and nadir SpO(2) (P = 0.007) were positively associated with PH. Clinical signs suggestive of respiratory abnormalities during sleep were not significantly correlated with the results of PSG. We conclude that the prevalence of OSA in patients with MPS VI was high, and the level of desaturation was positively correlated with PH. Symptoms during sleep were not associated with PSG findings, which suggests that this population should undergo routine PSG as earlier as possible. This study provides baseline data to estimate the potential impact of specific treatments in the sleep abnormalities presented by patients with MPS VI.