Nonspecific interstitial pneumonia (NSIP).

Nonspecific interstitial pneumonia (NSIP) represents one histologic subtype of idiopathic interstitial pneumonia (IIP). NSIP is typified by temporal homogeneity and less profusion of fibroblastic foci than is seen with usual interstitial pneumonia (UIP), the most common IIP. Clinically patients with NSIP present with similar symptoms (cough and dyspnea) when compared to patients with UIP. The duration of these symptoms prior to presentation is variable. The finding of fever may be more common in NSIP and clubbing may be more common in UIP; however, both findings can be seen in either UIP or NSIP. Physiological findings typically demonstrate a restrictive ventilatory defect with decreased gas transfer; little difference exists between UIP and NSIP. High resolution computed tomography (HRCT) scans are more likely to show honeycombing with UIP and a ground-glass pattern with NSIP, however, either of these findings can be seen with UIP or NSIP. The most striking differential feature between NSIP and UIP is the markedly better prognosis for patients with NSIP, a finding that cannot be explained by baseline differences in physiology or radiographic features. In this article we explore the clinical, physiological, and radiographic features of NSIP. We also review available information regarding response to therapy and prognosis.