Elevated serum IgG4 levels in two cases of paragonimiasis.

Paragonimiasis is a parasitic pleuropulmonary infection caused by eating raw crustaceans and wild boar meat and this infection is endemic in Asia. We herein report two cases of pulmonary P aragonimus westermani infection associated with elevated levels of serum immunoglobulin (Ig) G4 and dense infiltration of IgG4-positive plasma cells in the lung lesions. Treatment with praziquantel resolved the pulmonary lesions and decreased the serum levels of IgG4. IgG4-related disease is a systemic disease occasionally involving the lungs and leads to increased serum levels of IgG4. Our findings suggest that P. westermani infection requires a differential diagnosis from IgG4-related diseases and the serum IgG4 level may be a potentially useful marker of P. westermani infection.