What hematologic abnormality is commonly associated with Diphyllobothrium latum infection?

• A. Megaloblastic anemia due to vitamin B12 deficiency
• B. Iron-deficiency anemia
• C. Sickle cell anemia
• D. Leukopenia

Answer: (A)

Diphyllobothrium latum infection commonly causes vitamin B12 deficiency because the tapeworm absorbs substantial amounts of vitamin B12 in the small intestine. Vitamin B12 is essential for DNA synthesis in red blood cell precursors, so its deficiency leads to impaired DNA replication, resulting in megaloblastic (macrocytic) anemia with large, immature red cells and often hypersegmented neutrophils. Clinically this presents as fatigue and pallor, and labs show macrocytosis with elevated methylmalonic acid and homocysteine. While other anemias can occur for different reasons, the distinctive hematologic change here is megaloblastic anemia due to B12 deficiency from the tapeworm.