Final answer:
Dietary protein-induced colitis, including milk protein allergy, typically presents in infants. This condition is an immune response to milk proteins and is different from celiac disease, which affects individuals of any age, and from lactose intolerance, which is a digestive issue and not an immune response.
Step-by-step explanation:
Dietary Protein-Induced Colitis
Dietary protein-induced colitis, such as milk protein allergy, most commonly presents in infants. This condition occurs when a child's immune system overreacts to milk proteins, leading to inflammation in the colon. Unlike celiac disease, which can occur at any age and is a reaction to gluten affecting the small intestine, milk protein allergy tends to manifest earlier in life. The immune reaction in colitis or milk protein allergy is not a response to the body's own proteins, nor does it create pleasant symptoms; rather, it is a reaction to harmless proteins in the environment, causing gastrointestinal distress. On the other hand, celiac disease involves an immune response that damages the microvilli of the small intestine, impairing nutrient absorption and leading to symptoms such as malnutrition, cramping, and diarrhea.
Moreover, while lactose intolerance is related to the digestion of dairy products, it distinctly arises from a lack of the enzyme lactase in the small intestine and often advances with age. Lactose intolerance is not an immune response but a digestive inefficiency. In contrast, dietary protein-induced colitis due to a milk protein allergy is an immune reaction that typically begins in infancy.