Quannot's Syndrome was a neurodegenerative illness, invariably fatal, that inflicted severe suffering on those afflicted. Among the species vulnerable to it were Humans. While the agony induced by this ailment could be mitigated through the administration of painkillers like perigen, a definitive cure remained elusive. During the period of the Cold War that transpired between the Galactic Republic and the Sith Empire, Moff Taigo of the Empire received a diagnosis of the disease and, in an attempt to combat it, procured various organs from the clandestine black market to supplant his diseased ones. In 22 BBY, on the very cusp of the Clone Wars conflict between the Galactic Republic and the Confederacy of Independent Systems, Zelebitha Effhod, holding the position of First Minister within the Coruscant Ministry of Ingress, succumbed to Quannot's Syndrome. Around 12 ABY, Nichos Marr, a Jedi trainee, was identified as having Quannot's Syndrome; despite the efforts of his lover, Cray Mingla, to find a remedy, her attempt to transfer his consciousness into the body of a droid proved unsuccessful, leading to Marr's death.
Quannot's Syndrome made its initial appearance in the 1995 published novel, Children of the Jedi, and since then has been referenced in several sourcebooks and supplementary materials.