Nonspecific interstitial pneumonia is an idiopathic interstitial pneumonia that occurs mainly in women, nonsmokers, and patients < 50 yr.
Compared to idiopathic pulmonary fibrosis (IPF), nonspecific interstitial pneumonia (NSIP) is an uncommon idiopathic interstitial pneumonia (see Overview of Idiopathic Interstitial Pneumonias). Most patients are women, are between the ages of 40 and 50, and have no known cause or association. However, a similar pathologic process can occur in patients with a connective tissue disorder (in particular, systemic sclerosis or polymyositis/dermatomyositis), in some forms of drug-induced lung injury, and in patients with hypersensitivity pneumonitis.
Clinical presentation is similar to that of IPF. Cough and dyspnea are present for months to years. Constitutional symptoms are unusual, although a low-grade fever and malaise are possible.
The diagnosis should be considered in patients with unexplained subacute or chronic cough and dyspnea. Diagnosis requires HRCT and always requires confirmation by surgical lung biopsy. NSIP is a diagnosis of exclusion that requires careful clinical review for possible alternative disorders, in particular connective tissue disorders, hypersensitivity pneumonitis, and drug toxicity.
Chest x-ray primarily shows lower-zone reticular opacities. Bilateral patchy opacities are also possible. HRCT findings include bilateral patchy ground-glass attenuation, irregular lines, and bronchial dilatation (traction bronchiectasis), generally with a lower lung zone distribution. Subpleural sparing is possible. Honeycombing is rare. More than half of patients have an increased percentage of lymphocytes in bronchoalveolar lavage fluid, but this finding is nonspecific.
Histologically, most patients have some degree of fibrosis. The main feature of NSIP is temporally homogenous inflammation and fibrosis, as opposed to the heterogeneity in usual interstitial pneumonia. Although the changes are temporally uniform, the process may be patchy, with intervening areas of unaffected lung.
Many patients respond to treatment with corticosteroids, with or without immunosuppressive drugs (eg, azathioprine, mycophenolate mofetil, cyclophosphamide). Prognosis seems to depend most on the degree of fibrosis found during surgical lung biopsy. In patients with primarily cellular disease, almost all patients survive at least 10 yr. However, with increasing fibrosis, survival worsens and in some series median survival for fibrotic NSIP is 3 to 5 yr.
Last full review/revision April 2013 by Harold R. Collard, MD
Content last modified November 2013