A rare inherited condition causing painful sensitivity to sound, carried by the men of the Picard family, whose presence in Shinzon helped confirm that he was Jean-Luc Picard's clone.
Shalaft's syndrome is a very rare congenital disorder in which even quiet sounds can cause severe pain. It can be corrected, and Jean-Luc Picard was treated for it in childhood; by his own account every male member of his family was born with it.
The condition is mentioned in the film Star Trek Nemesis. After the Enterprise-E crew meet Shinzon, the young human who has seized power on Romulus, Doctor Crusher analyses a sample of his blood. Her examination shows not only that he is genetically identical to the captain but that he carries Shalaft's syndrome, a detail that leaves Picard in no doubt about what he is looking at.
The finding supports Shinzon's story that the Romulans grew him from Picard's cells in a plan to replace the captain with an agent, later abandoned, after which the child was sent to the dilithium mines of Remus.