[IgG4-related lung disease: a case report and review of the literature].

Objective: To describe the clinical features of IgG4-related lung disease.

Method: The clinical symptoms, laboratory tests, radiographic patterns, histopathological features and therapeutic management of a patient with IgG4-related lung disease were described and the literatures were reviewed.

Results: A 41-year-old male without significant symptoms was admitted to our department because of diffuse opacities on regular X-ray examination. Chest HRCT revealed diffuse ground-glass opacities (GGOs) and reticular opacities in both lungs, predominantly in the middle fields. Thoracoscopic lung biopsy was performed, and pathological examination of the lung tissues found massive lympho-plasma cell infiltration and collagen deposition along the alveolar septa and bronchovascular bundles on HE staining. Obliterative phlebitis and thickening of alveolar septa were observed. IgG4 immunostaining revealed predominant IgG4(+) plasma cells. IgG4-related lung disease was diagnosed combined with elevation of serum IgG4 concentration (3.07 g/L). The patient received oral prednisone at the dose of 30 mg per day for one month and then the dose was tapered. Four months later a CT scan revealed that the GGOs disappeared and only some reticular opacities and honeycombing changes remained. The serum IgG4 concentration decreased to 1.99 g/L. Twenty-one articles with 65 cases of IgG4-related lung disease were collected through PubMed search engine. Extrapulmonary organs were involved in 38 cases, especially the pancreas. Serum IgG4 concentrations were assessed in 36 cases and elevated in 34. Four radiographic patterns were identified: solid nodule type (55.4%), alveolar interstitial type (26.2%), bronchovascular type (13.8%) and round-shaped GGO type (4.6%). Glucocorticoids were prescribed to 23 patients with a favorable response except one treatment failure.

Conclusion: IgG4-related lung disease is a rare disorder and easily overlooked in clinical practice. The lung maybe the only target organ, but extrapulmonary organ involvement is the most common discoveries. The diagnosis of IgG4-related lung disease depends on the elevation of serum IgG4 and characteristic histopathological features. Glucocorticoid therapy is very effective and most patients have a good prognosis.