A Cameron lesion is a linear erosion or ulceration of the mucosal folds lining the stomach where it is constricted by the thoracic diaphragm in persons with large hiatal hernias. The lesions may cause chronic blood loss resulting in iron deficiency anemia; less often they cause acute bleeding. Treatment of anemia with Cameron lesions includes iron supplements and acid suppression by a proton-pump inhibitor (PPI). Surgical hernia repair is sometimes needed. Signs and symptoms Cameron lesions may lead to bleeding, and may be associated with heartburn or other symptoms of reflux. Generally, Cameron lesions do not cause pain. Cause The diaphragm separates the chest from the abdomen. The esophagus (swallowing tube) passes through the hiatal opening in the diaphragm to reach the stomach. With a hiatal hernia, part of the stomach is displaced upwards into the chest (Figure 1). Large hiatal hernias may cause chronic gastrointestinal blood loss leading to iron deficiency anemia. One study in people with hernias showed mean blood loss of 15ml (a tablespoonful) per day in those with anemia, compared to 3 ml per day in those without anemia. In one report 10% of 100 people investigated for iron deficiency anemia had a large hiatal hernia. A 1967 review found that 20% of 1305 individuals having surgery for hiatal hernia were anemic. Cameron in 1976 compared 259 people with large hiatal hernias visible on chest x-ray with 259 controls without hernias. Present or past anemia, usually with proven iron deficiency, was found in 10.4% of those with hernias, significantly more than 0.4% of controls, p<0.001. Surgical hernia repair usually prevents anemia recurrence; in 2 large series, post-operative follow-up showed anemia had resolved in 71-92% of subjects. An isotope study showed correction of blood loss after hernia repair. These findings showed that the hernia was the usual cause of the anemia. Cameron lesions cause blood loss from hiatal hernias Based on their surgical observations, Windsor and Collis in 1967 proposed that blood loss was due to local trauma to the stomach where it rides to and fro in the hiatus on respiration. Boutelier et al. noted on gastroscopy ulcers and erosions at the level of the neck of the hernia in individuals with acute and chronic bleeding, but no detailed description was given. Cameron and Higgins in 1986 described linear gastric erosions, later called "Cameron lesions", in people with x-rays showing one-third or more of the stomach