What type of disorder is primarily characterized by an enzyme deficiency?

Lactose intolerance is characterized primarily by an enzyme deficiency, specifically a deficiency of lactase. Lactase is the enzyme responsible for breaking down lactose, the sugar found in milk and dairy products. Individuals with lactose intolerance have insufficient levels of lactase, leading to difficulty digesting lactose. This results in gastrointestinal symptoms such as bloating, gas, and diarrhea when lactose-containing foods are consumed.

The condition is distinct from other options like a milk allergy, which is an immune response to proteins in milk rather than a digestive enzyme issue. Celiac disease is an autoimmune disorder triggered by gluten in certain grains, and irritable bowel syndrome is a functional gastrointestinal disorder that involves various symptoms but isn’t specifically tied to an enzyme deficiency. Thus, the defining characteristic of lactose intolerance as an enzyme deficiency makes it the correct response to this question.