Ectopic paragonimiasis presenting as massive pericardial effusion in a child: A rare diagnostic challenge

To report a rare pediatric case of ectopic paragonimiasis presenting as isolated massive pericardial effusion and to emphasize key diagnostic clues for early recognition in endemic regions.

We describe a 10-year-old boy from an endemic area in China who presented with acute gastrointestinal symptoms and recurrent massive pericardial effusion without respiratory manifestations. Diagnostic evaluation included pericardial fluid analysis, microbiological testing, echocardiography, cardiac magnetic resonance imaging(MRI), serological testing for Paragonimus IgG, therapeutic response assessment, and histopathological examination following surgery.

Despite repeated pericardiocenteses and empirical anti-infective therapy, the effusion persisted. Laboratory testing revealed exudative pericardial fluid with negative cytology, acid-fast staining, and metagenomic next-generation sequencing(mNGS), while peripheral eosinophilia and stool ova were absent. Echocardiography showed a characteristic "cocoon-like" pericardial pattern, and serology was positive for Paragonimus IgG.The patient improved after praziquantel and corticosteroids, but progressive pericardial thickening required pericardiectomy, which confirmed necrotizing granulomatous inflammation. The patient recovered with no recurrence during follow-up.

Paragonimiasis should be considered in children from endemic areas with unexplained or recurrent pericardial effusion, even in the absence of pulmonary involvement or eosinophilia. Epidemiological exposure, characteristic echocardiographic findings, and serology are critical for diagnosis, and timely anti-parasitic therapy with surgical intervention when necessary may prevent constrictive pericarditis.