Non-specific Interstitial Pneumonia [1]

Clinical features: Patients with NSIP tend to be younger than those with UIP (mean age 46-57 [2-5]). The ratio of patients with NSIP to those with UIP was 14 to 63 in one series, in which those with connective tissue diseases or environmental exposures were excluded from NSIP cases [2]. Females predominate 1.4:1 [1]. Symptoms and PFTs are similar to those of UIP [2]. As with UIP, some cases have associated conditions such as connective tissue disease or may represent hypersensitivity pneumonia, drug reaction, or slowly resolving acute lung injury; others are idiopathic [1].

Radiographic Changes

The CT shows subpleural and patchy, bilateral lower lung zone opacities with ground-glass and irregular lines.

Contrast this CT with that of UIP.

In a study of 7 patients with biopsy confirmed, untreated NSIP, radiographs showed patchy, bilateral opacities involving the mid and lower lung zones preferentially. CT showed ground-glass ± consolidation ± irregular lines, which, after treatment with steroids, resolved (3), improved (3), or persisted (1) [5].

Histologic Features

Part of this biopsy shows normal alveolar walls next to walls that are widened (arrows), have increased numbers of chronic inflammatory cells, and type II cell hyperplasia. There are increased numbers of alveolar macrophages. Fibrosis is minimal. A respiratory bronchiole is at the lower left (RB).

In another area from the same biopsy, a cellular alveolitis (left) blends with a more fibrotic region to the right. Although alveolar collapse is marked here, architectural distortion (honeycombing) is rare, and resolution is still possible.

Bronchiolitis obliterans organizing pneumonia--fibroblast focus

Rare fibroblast foci (F) were found in this biopsy. This one fills a respiratory bronchiole (note the respiratory epithelium) and spreads into adjacent alveoli near the top in a pattern resembling BOOP. However, the major pattern was an interstitial pneumonia with little airspace organization.

Summary of histologic features of NSIP [1,3]


The disease usually responds to steroids. In one series 10% (5/48) died but 44% recovered completely, 38% remained stable or improved, and 8% died of other causes [3]. In another study, the median survival was 13 y [2]. When the cases of NSIP were divided into cellular (N=7) and fibrotic (N=22) types, it was found that those with the cellular type all survived 10 years, but that those with the fibrotic type had a 90% survival at 5 years and a 35% survival at 10 years [6].


1. Katzenstein A-L, Myers J. Idiopathic pulmonary fibrosis. Clinical relevance of pathologic classification. Am J Respir Crit Care Med 1998; 157:1301-1315.

2. Bjoraker J, Ryu J, Edwin M, Myers J, Tazelaar H, Schroeder D, Offord K. Prognostic significance of histopathologic subsets in idiopathic pulmonary fibrosis. Am J Respir Crit Care Med 1998; 157:199-203.

3. Katzenstein A-L, Fiorelli R. Nonspecific interstitial pneumonia/fibrosis. Histologic features and clinical significance. Am J Surg Pathol 1994; 18:136-147.

4. Cottin V, Donsbeck A-V, Revel D, Loire R, Cordier J-F. Nonspecific interstitial pneumonia. Individualization of a clinicopathologic entity in a series of 12 patients. Am J Respir Crit Care Med 1998; 158:1286-1293.

5. Park J, Lee K, Kim J, Park C, Suh Y, Choi D, Kim K. Nonspecific interstitial pneumonia with fibrosis: radiographic and CT findings in seven patients. Radiology 1995; 195:645-648.

6. Travis W, Matsui K, Moss J, Ferrans V. Idiopathic nonspecific interstitial pneumonia: prognostic significance of cellular and fibrosing patterns: survival comparison with usual interstitial pneumonia and desquamative interstitial pneumonia. Am J Surg Pathol 2000; 24:19-33.

Clinical summary Discussion

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