What condition is characterized by the inability to digest lactose due to a lack of the enzyme lactase?

Lactose intolerance is characterized by the body's inability to properly digest lactose, the sugar found in milk and dairy products. This occurs due to a deficiency of the enzyme lactase, which is necessary for breaking down lactose into glucose and galactose, simpler sugars that can be absorbed by the intestines. When lactose is not adequately digested, it can lead to various gastrointestinal symptoms such as bloating, diarrhea, and gas after consuming dairy products.

In contrast, appendicitis is an inflammation of the appendix and does not relate to lactose digestion. Celiac disease is an autoimmune disorder triggered by the ingestion of gluten, leading to damage in the small intestine, which is a different condition altogether. Gastroesophageal reflux disease (GERD) involves the backflow of stomach acid into the esophagus and is unrelated to the digestive processing of lactose. Therefore, the specific connection of lactose intolerance to the absence of lactase makes it the correct choice for this question.