Nonspecific interstitial pneumonia (NSIP) is one type of idiopathic interstitial pneumonia (IIP). The other IIPs include usual interstitial pneumonia (UIP)/idiopathic pulmonary fibrosis, (IPF)/cryptogenic fibrosing alveolitis (CFA), desquamative interstitial pneumonia (DIP), respiratory bronchiolitis associated interstitial lung disease (RB-ILD), acute interstitial pneumonia (AIP), lymphocytic interstitial pneumonia (LIP), and cryptogenic organizing pneumonia (COP)/bronchiolitis obliterans organizing pneumonia (BOOP).
NSIP is "nonspecific" in that it presents similarly to other IIPs, but lacks the histopathologic features that characterize the individual disorders. In this review, the etiology, pathogenesis, clinical manifestations, diagnosis, treatment, and prognosis of NSIP are discussed. The pathology of NSIP is described separately. (See "Idiopathic interstitial pneumonias: Clinical manifestations and pathology".)
The term NSIP has been associated with many medical conditions, although a causal link has not been identified. In addition, it may be idiopathic.
HIV infection — NSIP is frequently identified in patients who have AIDS [1-6]. In one observational study of 110 patients with AIDS and interstitial lung disease, NSIP was detected in 38 percent . Nearly half of the patients had normal chest radiographs. A study performed since the introduction of HAART found that 7 percent of HIV patients admitted with ILD had NSIP .
Connective tissue disease — Several connective tissue disorders including polymyositis-dermatomyositis, rheumatoid arthritis, Sjögren’s syndrome, and systemic sclerosis have been associated with NSIP [7-16]. Although not all patients with ILD in the context of a known collagen vascular disease are biopsied, several studies have shown NSIP to be a common pattern.