Mikulicz's disease (MD) is a unique IgG4-related systemic disease indicated by enlargement of the lachrymal and salivary glands and which differs substantially from Sjögren's syndrome. A male patient with pleural effusion, swelling of the submandibular glands, and swelling of the paraaortic, mediastinal, and pararenal lymph nodes was diagnosed with MD. Analysis of peripheral CD4+ T cells from the patient revealed deviation of the Th1/Th2 balance to Th2. Prednisolone therapy ameliorated the disease and corrected the Th1/Th2 imbalance.