Paragonimiasis — DTM&H MCQ
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Correct answer: D — Paragonimiasis
The correct answer is D, Paragonimiasis. This man has the classic triad of chronic cough or abdominal symptoms with eosinophilia, a history of eating raw freshwater crabs (the intermediate host of Paragonimus westermani metacercariae), and pleural effusion on imaging, with large golden-brown operculated eggs seen on sputum microscopy. Ingested metacercariae migrate from the gut through the diaphragm into the pleural space and lungs, where adult flukes deposit these characteristic eggs, which are coughed up or swallowed and passed in stool. This exposure history and egg morphology are pathognomonic and distinguish paragonimiasis from other eosinophilic lung syndromes; treatment is praziquantel. Why the other options are wrong: E. Pulmonary tuberculosis: TB can cause pleural effusion and is a common misdiagnosis radiologically, but it does not cause peripheral eosinophilia or golden-brown operculated eggs in sputum, and there is no crab-eating link. B. Strongyloides pulmonary migration: causes transient Loeffler-like pneumonitis during larval migration with larvae (not operculated eggs) potentially seen in sputum, and is acquired by skin penetration from soil, not crab ingestion. A. Tropical pulmonary eosinophilia: results from hypersensitivity to lymphatic filarial antigens, producing diffuse reticulonodular changes and very high eosinophilia, but no eggs are found in sputum since it is an immune reaction, not direct infection. C. Ascaris pulmonary migration: larvae transiently migrate through lungs causing eosinophilic pneumonitis, but Ascaris eggs are non-operculated (barrel-shaped, mammillated) and found in stool once adults mature in the intestine, not golden-brown operculated eggs in sputum. Key point: Golden-brown operculated eggs in sputum with pleural effusion and a raw freshwater crab-eating history clinches paragonimiasis, treated with praziquantel.
Reference: BNF (NICE), Praziquantel: indications and dose, https://bnf.nice.org.uk/drugs/praziquantel/