A disease that is characterized by the creation of an MMORPG account, such as World of Warcraft, Runescape or Tibia, in order to complete all of the quests available even if entails paying a monthly fee.
Mark: "How long has Kyle been playing WOW?"

Joe: "He's not logging out until he finishes the last quest."

Mark: "I'm gonna say that we've lost him to questly syndrome."
by Cedarus September 12, 2011
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