A professor is talking about a sleep-related disease in which a person stops sleeping in middle age, despite having slept normally in the earlier years. The professor says that this disease occurs when a person inherits a defect in the gene for the prion protein. Which of the following diseases is most likely being discussed in this scenario?
a. REM behavior disorder
b. Sleep apnea
c. Narcolepsy
d. Fatal familial insomnia