Four members of a family, a mother, her two sons, and the mother's second cousin, presented with a history of isolated cataplexy without excessive daytime sleepiness or other symptoms typical of narcolepsy. They were polygraphically monitored during one night followed by a day of multiple nap tests. No subject manifested objective daytime sleepiness as measured by short latencies to sleep onset during daytime naps, and no subject exhibited periods of sleep onset rapid eye movement sleep in either the night or nap recordings. The incidence of isolated cataplexy in this family was traced by history through six generations. We conclude that isolated cataplexy in this family is a genetically transmitted dominant trait with incomplete penetrance which occurs independently of daytime sleepiness and the full-blown narcolepsy syndrome.
Hartse, Kristyna M.; Zorick, Frank J.; Sicklesteel, Jeanne M.; and Roth, Thomas
"Isolated Cataplexy: A Familial Study,"
Henry Ford Hospital Medical Journal
: Vol. 36
Available at: https://scholarlycommons.henryford.com/hfhmedjournal/vol36/iss1/7