Qong-Hegh

Qong-Hegh was a hereditary genetic disease that afflicts certain Klingons.

It was commonly associated among the lower classes within the Klingon Empire and was considered a shame by those who were affected by it. As such, there was no cure for the disease. Furthermore, New Klingons suffering from it were quite embarrassed due to the social stigma involved with it despite the fact that they abandoned the class based system.

During the elaborate plot orchestrated by the Klingons regarding the Tholian Incident, it was stated that Kalrind was suffering from the disease in order to explain the medicines she took which were actually drugs that were designed to surpress her violent tendencies and create a second personality as part of the scheme. (TOS novel: Timetrap)