Hypoventilation in REM sleep in a case of 17p11.2 deletion (Smith-Magenis syndrome)

We describe a 2-year-old baby affected by Smith-Magenis syndrome (SMS), due to 17p11.2 deletion, who presented repeated episodes of hemoglobin desaturation during REM sleep. The boy, aged 14 months, presented a phenotype characterized by psychomotor delay, right posterior plagiocephaly, telecanthus, strabismus, upslanting palpebral fissures, broad hypoplastic nasal bridge, short philtrum, deep ring shaped skin creases around the limbs, proximal syndactyly, bilateral hypoacusia. Polysomnographic (PSG) recording showed episodes of REM related hypoventilation (hemoglobin desaturations without apneas or hypopneas). Sleep disorders are present in almost all the cases of SMS, but very few reports describe the sleep-related respiratory patterns. The finding of REM hypoventilation in SMS does not allow an unequivocal interpretation. It could reflect a subclinical restrictive respiratory impairment or, alternatively, an impairment of central respiratory control during REM sleep. In SMS children, respiratory abnormalities during sleep, and in particular during REM sleep, may cause sleep disruption, reduction of time spent in REM sleep, and daytime sleepiness. We therefore suggest that some sleep abnormalities described in SMS could be consequent to Sleep Disordered Breathing, and in particular to REM hypoventilation. Sleep studies in SMS should include the recording of respiratory parameters.