Introduction: NSIP is one of the better variants of Interstitial lung disease in terms of outcomes. Recent ATS/ERS guidelines has classified idiopathic NSIP (iNSIP) as distinct entity among all interstitial pneumonias. Often associated with connective tissue diseases (CTD) and less frequently with drug toxicity, infection and smoking. Majority of cases still remain idiopathic which forms the major fraction of NSIP pool. Timely diagnosis with early treatment has excellent 5-year survival figures.

Epidemiology: With a prevalence of  around 1 to 9 per 100000 population NSIP is more commonly seen in females and non-smokers in their fifth decade of life. 15% of patients diagnosed with NSIP are found to have an underlying CTD. Almost all the studies from north India described male preponderance of ILD with CTD as predominant cause.

Clinial Features and Diagnosis: NSIP patients are usually middle age nonsmoking females. Typical symptoms of chronic cough, weight loss and breathlessness are almost universal. Fine basal inspiratory crepitations with restrictive type defect due to reduced FVC and DLCO in Spirometry. Multimodality approach involving serological, radiological and histopathological tests are required to rule out CTD, ocular, renovascular, occupational and drug exposure related factors.

Radiological diagnosis based of chest X-ray alone is difficult as it can mimic conditions such as pneumonia or pulmonary oedema and ARDS. However, HRCT shows pretty straightforward changes of classical bilateral subpleural reticular opacities with traction bronchiectasis and fibrosis without honeycombing. Lung biopsy predominantly shows diffuse homogenous interstitial inflammation and fibrosis with relatively preserved alveolar architecture.

Management: There is no clear consensus regarding treatment guidelines. Treatment with corticosteroids is most effective in cellular NSIP or organizing pneumonia, but not so in fibrotic pattern. Milder disease can be followed up with serial monitoring. Cyclophosphamide has been most frequently studied drug with promising results as steroid sparing therapy. Recent literature also supports use of rituximab for   treatment resistant and non responsive patients. Overall prognosis of idiopathic NSIP is favourable as compared to its counterparts with a 5-year mortality  rate of 20%

Keywords: Idiopathic NSIP, Connective tissue Disease(CTD), Ground glassing