Mallory-Weiss syndrome, often referred to on the show as a Mallory-Weiss tear is physical damage to the mucous membranes found at the junction of the esophagus and the stomach. In a normal patient, this junction is protected by a flap that keeps out stomach acid, which can damage the junction, but not the lining of the stomach. However, if the junction is constantly exposed to stomach acid, it can lead to open tears which result in bleeding and coughing up blood.
The condition can be caused by many types of gastrointestinal problems, but is more common in alcoholics, conditions that cause or induce vomitting (such as undergoing chemotherapy or in bulimia) or in patients with severe lung diseases such as tuberculosis. It is a rare complication of the abuse of NSAIDs such as aspirin.