Diphyllobothrium latum


Diphyllobothrium latum


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USMLE® Step 1 questions

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Diphyllobothrium latum

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USMLE® Step 1 style questions USMLE

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A 37-year-old woman is hospitalized for small bowel obstruction. Two months ago she traveled around the Baltic Sea and ate several meals consisting of raw fish. Temperature is 38.1°C (100.6°F), blood pressure is 125/77 mmHg, and pulse is 90/min. Laboratory studies reveal a hemoglobin of 9.1 g/dL (reference range: 12.0-16.0 g/dL) and mean corpuscular volume of 109 μm3 (reference range: 80-100 μm3). A stool sample is collected and is found to contain several eggs. Which of the following pathologies is most likely responsible for this patient’s clinical presentation? 

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Diphyllobothrium latum p. , 157

Diphyllobothrium latum

BNaN deficiency p. 428

disease association p. 158

presentation p. 157

vitamin BNaN deficiency p. 67

Megaloblastic anemia p. 425, 428

Diphyllobothrium latum p. , 157

Vitamin BNaN deficiency p. 428

Diphyllobothrium latum p. , 157, 158


Diphyllobothrium latum is a parasitic cestode (flatworm) contracted by ingesting raw freshwater fish, hence its reputation as the fish tapeworm. The parasite attaches to the lining of the intestine and disrupts the absorption of vitamin B12, causing its deficiency. It presents with features of vitamin B12 deficiency, including macrocytic megaloblastic anemia. Symptoms can include abdominal pain, diarrhea, weight loss, and anemia.


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