A 65-year-old client with a history of Crohn's disease presents to the clinic with complaints of fatigue and diarrhea. Which laboratory finding should the nurse anticipate as most characteristic of the expected nutritional deficiency?

Vitamin B12 deficiency in Crohn's disease causes megaloblastic anemia with pale conjunctiva and glossitis. Other options are associated with iron, vitamin A, or calcium deficiencies.

Understanding the Pathophysiology
In Crohn's disease, chronic inflammation can affect any part of the gastrointestinal tract, but it has a particular predilection for the terminal ileum. The terminal ileum is the specific site where vitamin B12 (cobalamin) is absorbed, a process that requires intrinsic factor. When this area is damaged by inflammation or surgically resected, the enterohepatic pathway for B12 absorption is disrupted. This leads to a progressive depletion of hepatic B12 stores and, eventually, a functional deficiency. The resulting condition is pernicious anemia, a megaloblastic anemia characterized by impaired DNA synthesis in rapidly dividing cells, including the hematopoietic cells in the bone marrow and the epithelial cells of the gastrointestinal tract ^[1].

Connecting the Deficiency to the Clinical Presentation
The question asks for the laboratory finding most characteristic of the expected nutritional deficiency. While the client's symptoms of fatigue and diarrhea are general, the correct answer points to the classic clinical signs of pernicious anemia. A deficiency in vitamin B12 leads to ineffective erythropoiesis and the production of abnormally large, oval-shaped red blood cells (macrocytes). The anemia causes tissue hypoxia, which manifests as pallor, readily visible in the conjunctiva. Simultaneously, the defective DNA synthesis affects the rapidly dividing epithelial cells of the tongue, leading to atrophic glossitis. The lingual papillae atrophy, giving the tongue a smooth, glossy, and beefy-red appearance. These two findings—pale conjunctiva and a smooth, red tongue—are hallmark clinical indicators of vitamin B12 deficiency anemia ^[1].

Why Other Options Are Less Characteristic
The other options represent deficiencies of different micronutrients, which are not the primary and most characteristic deficiency expected from terminal ileum pathology.
- Option 1 (Brittle nails and hair loss) is classically associated with iron deficiency anemia, which can also occur in Crohn's disease due to chronic blood loss or duodenal involvement, but it is not the most specific deficiency linked to ileal dysfunction.
- Option 3 (Dry, scaly skin and night blindness) points to a deficiency of fat-soluble vitamins, specifically vitamin A. While malabsorption of fat-soluble vitamins can occur in extensive small bowel disease, B12 deficiency is the most direct and predictable consequence of terminal ileal involvement or resection.
- Option 4 (Muscle cramps and bone pain) is suggestive of calcium and/or vitamin D deficiency, which is a long-term complication of malabsorption and corticosteroid use in Crohn's disease, but it is not the immediate and most characteristic finding related to B12 malabsorption at the terminal ileum.

For a client with Crohn's disease and a history suggesting ileal involvement, the nurse should anticipate laboratory findings consistent with pernicious anemia. The clinical assessment would reveal a pale conjunctiva and a smooth, red tongue, prompting further diagnostic evaluation of serum vitamin B12 levels, complete blood count, and possibly methylmalonic acid and homocysteine levels. The study by Calafat et al. confirms that patients with Crohn's disease and ileocolic resection are at significant risk for B12 deficiency, underscoring the need for routine monitoring and consideration of supplementation strategies in this population ^[1].