Histopathological Diagnosis of Pulmonary Paragonimiasis: A Case Report from Ecuador

Paragonimiasis is a foodborne trematode infection caused by Paragonimus spp. that primarily affects the lungs and may mimic tuberculosis, pulmonary mycoses, abscess, or malignancy because of its nonspecific clinical and radiological manifestations. Definitive diagnosis relies on the identification of Paragonimus eggs in respiratory specimens or tissue. We report a 17-year-old female from the Ecuadorian Amazon with a 5-year history of chronic cough and recurrent hemoptysis. Repeated examinations of sputum and stool were negative for Paragonimus eggs, and GeneXpert MTB/RIF assays and mycobacterial cultures were negative. Chest computed tomography performed approximately 1 year apart demonstrated a persistent 12 × 13-mm mixed solid-cystic lesion with central necrosis in the left upper lobe. Marked peripheral eosinophilia and elevated serum IgE were present. Bronchoalveolar lavage showed no parasitic structures, and a CT-guided percutaneous lung biopsy was nondiagnostic. Video-assisted thoracoscopic resection was subsequently performed. Histopathological examination revealed eosinophil-rich granulomatous inflammation and multiple thick-shelled, operculated eggs that were morphologically consistent with Paragonimus spp. Species-level identification was not performed. A detailed epidemiological history disclosed frequent consumption of raw freshwater crabs and shrimp. Following surgical resection and praziquantel treatment, respiratory symptoms resolved and eosinophilia markedly decreased; the patient remained asymptomatic during 1 year of follow-up. This case emphasizes that pulmonary paragonimiasis should be considered in patients from endemic areas with chronic hemoptysis, eosinophilia, compatible pulmonary lesions, and relevant dietary exposure, even when conventional parasitological examinations are negative. We highlight the value of histopathological examination of adequately sampled lung tissue when conventional parasitological investigations are repeatedly negative.