Nonspecific Interstitial Pneumonia
Nonspecific interstitial pneumonia (NSIP) is an idiopathic interstitial pneumonia. It is much less common than idiopathic pulmonary fibrosis (IPF). 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 autoimmune myositis), in some forms of drug-induced pulmonary disease, and in patients with hypersensitivity pneumonitis.
Clinical presentation of NSIP 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 of nonspecific interstitial pneumonia 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 dilation (traction bronchiectasis), generally with a lower lung zone distribution. Subpleural sparing is possible. Honeycombing is rare.
Bronchoalveolar lavage fluid has an increased percentage of lymphocytes in more than half of patients, but this finding is nonspecific.
Surgical lung biopsy is required for a diagnosis of NSIP. 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 with nonspecific interstitial pneumonia 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 years. However, with increasing fibrosis, survival worsens and in some series median survival for fibrotic NSIP is 3 to 5 years.
Nonspecific interstitial pneumonia is uncommon; most patients are women, are between the ages of 40 and 50, and have no known risk.
Exclude connective tissue disorders (particularly systemic sclerosis and autoimmune myositis), drug-induced lung injury, and hypersensitivity pneumonitis and do surgical lung biopsy.
Treat with corticosteroids, with or without immunosuppressive drugs (eg, azathioprine, mycophenolate mofetil, cyclophosphamide).
Prognosis is worse if biopsy shows more fibrosis.