A 58-year-old man comes to the office due to 2 months of exertional shortness of breath and easy fatigability. The patient has no chronic medical problems and takes no medications. He eats a balanced diet. He does not use tobacco, alcohol, or illicit drugs. Vital signs are within normal limits. Physical examination shows conjunctival pallor and areas of depigmentation on the arms suggestive of vitiligo. The tongue appears shiny. The spleen is not palpable. The remainder of the examination is normal. Laboratory results are as follows: Which of the following is the most likely cause of this patient's current symptoms?

Question

A 58-year-old man comes to the office due to 2 months of exertional shortness of breath and easy fatigability.  The patient has no chronic medical problems and takes no medications.  He eats a balanced diet.  He does not use tobacco, alcohol, or illicit drugs.  Vital signs are within normal limits.  Physical examination shows conjunctival pallor and areas of depigmentation on the arms suggestive of vitiligo.  The tongue appears shiny.  The spleen is not palpable.  The remainder of the examination is normal.  Laboratory results are as follows:  Which of the following is the most likely cause of this patient's current symptoms?

Quizplus · Accepted Answer

Explanation: 11ec25c8_d0e5_7c74_bc81_b1d88dc1ea5c_MD0003_00 This patient's macrocytic anemia, mild thrombocytopenia/leukopenia, and glossitis (smooth, shiny tongue) indicate likely vitamin B₁₂ deficiency. The leading cause of vitamin B₁₂ deficiency is pernicious anemia, an autoimmune condition associated with antibodies against intrinsic factor (a protein carrier crucial for vitamin B₁₂ absorption). Most cases occur in older patients who have other autoimmune conditions (eg, vitiligo, autoimmune thyroid disease). ₁₂ ₁₂ Because vitamin B₁₂ serves as a crucial cofactor for DNA synthesis, deficiency often disproportionately affects rapidly dividing cells; common manifestations include: ₁₂ Megaloblastic anemia (eg, macrocytosis, hypersegmented neutrophils, anemia, mild leukopenia/thrombocytopenia) due to impaired hematopoiesis Glossitis due to impaired replication of gastrointestinal epithelium The diagnosis of pernicious anemia can be confirmed by the detection of anti-intrinsic factor antibodies; treatment with vitamin B₁₂ supplementation is generally curative. ₁₂ (Choice B) Patients with hypothyroidism from autoimmune thyroiditis usually develop normocytic, normochromic anemia (due to bone marrow hypoproliferation). Occasionally, mild macrocytic anemia can occur, but no megaloblastic changes or other signs of vitamin B₁₂ deficiency (eg, glossitis) would be present. Most cases arise in young women. ₁₂ (Choice C) Nutritional folate deficiency, which can also cause megaloblastic anemia, is quite rare in developed countries due to the fortification of grain with folate. However, folate body stores are lower than those of vitamin B₁₂ and can be depleted in a few months when nutrition is poor (eg, severe alcohol abuse). This patient eats a balanced diet and is unlikely to have folate deficiency. ₁₂ (Choice D) Dietary vitamin B₁₂ deficiency is uncommon in those who eat a balanced diet because the vitamin is found in a wide range of assessable animal proteins (eg, meat, dairy, eggs) and total body stores are generally sufficient for >1 year (total stores are 2-5 mg and daily requirement is ~2 µg/day). However, patients with long-standing poor nutrition (eg, chronic alcoholic use) or vegan dietary habits may be at risk. ₁₂ (Choice E) Aplastic anemia is associated with the destruction of hematopoietic stem cells, leading to the replacement of bone marrow with fat. Although pancytopenia is common, macrocytosis is rarely seen and glossitis would be atypical. Educational objective: Pernicious anemia, an autoimmune condition associated with antibodies against intrinsic factor, is the most common cause of vitamin B₁₂ deficiency. It occurs most often in older adults with other autoimmune conditions. Patients generally have megaloblastic anemia, atrophic glossitis (smooth, shiny tongue), and/or neurologic abnormalities (eg, lower extremity paresthesia, subacute combined degeneration). ₁₂

A 58-Year-Old Man Comes to the Office Due to 2