Objectives: To observe the immunohistochemical staining of IgG4 in nonspecific interstitial pneumonia (NSIP) and to study the clinicopathological features of IgG4-related NSIP.
Methods: Retrospective analysis was carried out for 32 patients with NSIP who had been admitted into Peking Union Medical College Hospital from November 2002 to October 2010. The diagnosis of NSIP was established by surgical lung biopsy and all specimens were fixed in neutral formalin and embedded in paraffin. Sections were cut for HE and immunohistochemical stain. According to the diagnostic criteria for IgG4-related disease, 4 cases were confirmed to be IgG4-related NSIP. The clinicopathological features including clinical history, laboratory examination, and pathologic evaluation were studied.
Results: The 4 patients with IgG4-related NSIP included 1 man and 3 women, with a median age of 48 years (range, 44 - 56 years). The presenting symptoms were dry cough or shortness of breath. One patient (1/4, 25.0%) was found to have a positive autoantibody but no cases showed positive RF in serum. The histological finding of the 4 cases was characterized by inflammatory cell infiltration in interstitium with fibrosis, and 1 case showed obliterative arteritis. The numbers of IgG4-positive plasma cells in the 4 cases were 42/hpf, 22/hpf, 11/hpf, and 33/hpf respectively, while the percentages of IgG4-positive to IgG-positive plasma cells were 70%, 71%, 57%, 43% respectively.
Conclusions: IgG4-related interstitial pulmonary disease can be characterized as the NSIP pattern. The pathological features of IgG4-related NSIP include infiltration of lympho-plasmacytes and eosinophils in interstitium with fibrosis, and lymphoid follicles are frequently identified in the area of lymphocyte aggregation, but obliterative arteritis is infrequently identified in the lesion. Immunohistochemical staining of IgG and IgG4 is very helpful for a definite diagnosis of IgG4-related disease.