Besides delivering oxygen through the body's circulatory system, heme is important in metabolism and human physiology. Porphyria is a genetic disease that is caused by an enzyme deficiency in heme production. Heme is synthesized from smaller molecules through several enzyme-catalyzed steps in a biochemical pathway. An enzyme deficiency in any of these steps inhibits heme production, causing porphyrins to accumulate and clog the pathway. The high level of porphyrins is responsible for the physical symptoms, such as port-colored urine, sensitivity to sunlight, and the mental instability that sometimes accompanies this disease.
Attacks occur when porphyrins become elevated, depending on the patient's tolerance.
Alcohol, smoking, or prescription drugs that cause the body to respond by accumulating porphyrins can precipitate attacks. Penton knew that there was no cure for porphyria, because its root cause is a defective gene. He placed Lyon on hematin, which is chemically synthesized heme from human or animal blood. Lyon quickly felt relief from the constant pain, but she did not recover from the extreme weakness for many months. Several laboratories are investigating the mysteries surrounding porphyria.