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5. Retreat with prednisone followed by azathioprine
The patient has idiopathic nonspecific interstitial pneumonia (NSIP) which is a distinct form of idiopathic interstitial pneumonia (1,2). It is clinically, radiologically and histologically distinct from idiopathic pulmonary fibrosis(IPF)/usual interstitial pneumonia(UIP). A diagnosis of NSIP requires exclusion of other causes of NSIP patterns (drugs, CVD). NSIP exhibits a uniform alveolar septal infiltrate of lymphocytes and plasma cells (1,2). Neutrophils, eosinophils, and histiocytes are inconspicuous and granulomas are rare in NSIP and, if present, should raise other considerations. Most important is that the character of the inflammatory process in NSIP is the same throughout the affected areas, without the temporal heterogeneity inherent in UIP (Figure 3).
Figure 3. Typical low power biopsy of NSIP (left) and UIP (right). Note the uniform alveolar septal infiltrates of lymphocytes and plasma cells in NSIP. In UIP fibrosis predominates over inflammation. “Fibroblast foci” represent microscopic zones of acute lung injury set against a backdrop of chronic scarring, thus contributing to the variegated appearance or temporal heterogeneity of UIP.
On thoracic CT NSIP usually shows ground glass opacities in a patchy distribution with subpleural sparing. IPF/UIP usually shows honeycombing with basilar predominance and subpleural disease.
Importantly, prognosis and treatment are different for NSIP. Prognosis is considerably better with NSIP which usually responds to corticosteroids, azathioprine or mycophenolate.
Our patient was restarted on prednisone 40 mg/day and transitioned from azathioprine to mycophenolate. His breathing subjectively improved and a taper of prednisone was started. However, after 2 months when his prednisone had been tapered to 20 mg/day and he became much shorter of breath and returned for a follow up visit. His SpO2 was 91% on 6 lpm continuous flow. His chest exam revealed bilateral crackles.
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