Paragonimiasis — DTM&H MCQ

Correct answer: E — Paragonimiasis

The correct answer is E, Paragonimiasis. This man has the classic triad for pulmonary paragonimiasis: chronic cough with pleuritic pain and intermittent haemoptysis mimicking tuberculosis, repeatedly negative sputum for TB, and a history of eating raw freshwater crab, which is the recognised route of infection with Paragonimus species endemic to Southeast Asia including Laos. Metacercariae in undercooked or pickled freshwater crab and crayfish are ingested, migrate through the diaphragm into the pleural space and lung parenchyma, and provoke an eosinophilic inflammatory response with peribronchial fibrosis, explaining the eosinophilia and TB-like radiological and clinical picture. Diagnosis is confirmed by finding operculate eggs in sputum or stool (swallowed sputum) or by serology, and praziquantel is the treatment of choice, though it remains an unlicensed drug in the UK and is used on a named-patient basis. Why the other options are wrong: C. Pulmonary tuberculosis: Sputum for TB is repeatedly negative and eosinophilia is not a feature of TB, which instead causes lymphocytic or neutrophilic inflammation. B. Chronic pulmonary aspergillosis: This typically occurs in patients with pre-existing cavitary lung disease or immunocompromise and is associated with Aspergillus IgG serology, not a dietary crab exposure history or marked eosinophilia. D. Strongyloides hyperinfection: This occurs in immunosuppressed hosts (notably on corticosteroids) via autoinfection from skin or gut, presenting with gram-negative sepsis and diffuse pulmonary infiltrates, not a chronic TB-mimicking picture linked to crab ingestion. A. Melioidosis: Caused by Burkholderia pseudomallei via soil or water contact in endemic Southeast Asia, it can mimic TB but is not linked to raw crab ingestion and does not typically cause marked eosinophilia. Key point: A TB-negative chronic cough with haemoptysis, eosinophilia and a history of raw freshwater crab ingestion in a Southeast Asian patient should trigger consideration of pulmonary paragonimiasis.

Reference: BNF (NICE), Praziquantel drug monograph (unlicensed status in UK), https://bnf.nice.org.uk/drug/praziquantel.html