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