Nonspecific interstitial pneumonia (NSIP) is a distinct clinical entity among idiopathic interstitial pneumonias (IIPs), characterized by uniform involvement of the alveolar septa with interstitial inflammation and variable amounts of fibrosis
. The diagnosis of NSIP involves a combination of clinical, radiological, and histopathological findings.
Clinical presentation
- NSIP predominantly affects middle-aged women who are never-smokers
- Common symptoms include dyspnea and cough
Radiological findings
- High-resolution computed tomography (HRCT) typically shows a reticular pattern with traction bronchiectasis and volume loss, predominantly involving the lower lung zones
- The CT pattern in patients with pathologic NSIP is more uniform than that in patients with pathologic usual interstitial pneumonia (UIP), and CT NSIP pattern is associated with better patient outcomes than is CT UIP pattern
Histopathological findings
- Lung biopsies show uniform thickening of alveolar walls with a spectrum of cellular to fibrosing patterns
- Specimens for histopathological evaluation are best obtained by surgical wedge biopsy to allow accurate recognition of the involvement patterns of these disorders
Differential diagnosis
- NSIP should be differentiated from other IIPs such as UIP, desquamative interstitial pneumonia, respiratory bronchiolitis-associated interstitial lung disease, cryptogenic organizing pneumonia, acute interstitial pneumonia, and lymphoid interstitial pneumonia
- NSIP may also mimic interstitial lung disease related to connective tissue diseases, which may often dominate the clinical picture or precede systemic findings
Association with autoimmune disorders
- Emerging evidence suggests that idiopathic NSIP may be the lung manifestation of undifferentiated connective tissue disease (UCTD)
- In more than 50% of patients diagnosed with idiopathic NSIP, evidence of autoimmune diseases develops within 2 years, suggesting a probable link between the clinical entity of idiopathic NSIP and autoimmune disorders
In conclusion, the diagnosis of NSIP is based on a combination of clinical, radiological, and histopathological findings. It should be differentiated from other IIPs and interstitial lung diseases related to connective tissue diseases. Emerging evidence suggests a possible link between idiopathic NSIP and autoimmune disorders.