Smith-Magenis Syndrome (SMS) is a complex rare genetic condition characterized by multiple congenital anomalies and behavior problems, including abnormal sleep patterns. The frequent nighttime awakenings and daytime sleepiness in SMS can significantly impact the individual and those caring for them. SMS is most commonly caused by a deletion on part of chromosome 17. As a result, individuals with SMS may have a disruption to their circadian rhythm, which is responsible for regulating several physiologic functions, including sleep.
The nighttime sleep disturbance in SMS is most commonly the result of a hormone, melatonin, being elevated during the daytime instead of the nighttime. The secretion of melatonin is inverted in many of those with SMS. Not all people with SMS who have sleep disturbance have this inverted melatonin release, suggesting it is not the only cause of sleep difficulties and therefore, it is also likely that environment and routine have a significant impact on sleep for people with SMS.
While SMS is a genetic condition, it rarely passed on from parent to child and most cases are due to a spontaneous genetic change occurring for unknown reasons. Misdiagnosis is unfortunately common due to similarities with other genetic conditions and SMS being a highly variable disorder.