Nonspecific Interstitial Pneumonia

Abstract

Nonspecific interstitial pneumonia (NSIP) represents a less common idiopathic interstitial pneumonia than usual interstitial pneumonia (UIP) with a much better prognosis. Most cases of NSIP are secondary to collagen vascular disease, hypersensitivity or drug toxicity. These secondary forms of NSIP help to explain why it is more often seen on CT than UIP. Unlike UIP, NSIP is characterized by a paucity of honeycombing on CT and greater ground-glass opacity and reticulation. Subpleural sparing when present may suggest the diagnosis. Unlike UIP, NSIP tends to exhibit histologic spatial and temporal homogeneity. When extensive bronchiectasis is seen in association with an NSIP pattern, collagen vascular disease must be considered. When air trapping is encountered, hypersensitivity pneumonitis must be excluded. Biopsy is usually reserved for those patients with an NSIP pattern who do not have a known underlying condition. If the diagnosis of NSIP can be made, immunotherapy may prevent progression and may even reverse some CT findings.