Plak S'ran, also known as Blood Killing, was a medical condition that afflicted the Vulcan race.
Known by its ancient designation, medically this disease was leukokupricytosis which was a progressive disorder where the hemocyanic blood cells became deformed and lost color. The resultant color stripped cells massed in major blood vessels where they blocked the flow of oxygen and caused edema in the lungs. The bone marrow deterioration made any replacement of new cells inadequate and as the deformed cells accumulated in the joints and spinal fluids, the victim's initial shortness of breath as well as chronic fatigue was replaced instead with severe joint pain, debility, wasting and eventually death. The L-Kc was genetically linked though it was undetectable by most sophisticated antigen scan. Any offspring of the victim had a 50% risk factor of carrying the disease. Once a person suffered from plak s'ran, the diseae was always fatal.
During ancient Vulcan history, it was considered a form of retribution for certain transgressions of decorum such as overt emotionalism where rapid breathing and ensuing exhaustion mimicked the disease's symptoms. There were a number of individuals who died some residual credence to this superstition. The vicim was typically not offered empathy as that was not the Way of the Vulcan and no inquiries were made to the individuals health as this was a breach of privacy. The simple sight of Healers who were involved with transfusions at times which offered a temporary reprieve from the pain was enough to inform those that were curious.