Co-occurrence of 16p13.11 microdeletion and ring chromosome 20 syndrome.

A previously healthy 16-year-old girl of Jamaican descent presented with a 1-year history of progressive daytime somnolence, sleep attacks (sudden irresistible episodes of sleep), and paroxysms of altered level of consciousness. Her parents also reported irritability, mood lability, and hyperphagia. Her history was notable for a mild learning disability diagnosed at 9 years of age. Before symptom onset, she attended regular class at school with average academic performance and was independent in instrumental activities of daily living. On examination, she was normocephalic and nondysmorphic and had no focal neurologic deficits.