Current status of idiopathic nonspecific interstitial pneumonia.
Pulmonary pathologists were aware of cases of idiopathic interstitial pneumonia (IIP) that morphologically did not fit Liebow's classification scheme. These cases were labeled as "cellular interstitial pneumonia" or "chronic interstitial pneumonia not otherwise specified." The term nonspecific interstitial pneumonia (NSIP) was first used in relation to a pattern of lung interstitial inflammation seen in association with human immunodeficiency virus (HIV) infection. In 1994 NSIP was used to indicate a group of subacute or chronic interstitial pneumonias characterized morphologically by interstitial inflammation or fibrosis or both, with preservation of the lung architecture and the absence of typical findings for any of the other main categories of IIP (mainly usual interstitial pneumonia, desquamative interstitial pneumonia, and bronchiolitis obliterans organizing pneumonia). Although these patients presented with "nonspecific" lung histology (categorized as cellular and fibrotic variants), and with a broad spectrum of associated clinical conditions, such as connective tissue diseases (CTDs), environmental exposure, and previous acute lung injury, they showed some peculiar clinical aspects, including favorable response to corticosteroid treatment and overall good prognosis.The clinical and radiographic profiles were better defined in the last decade. The NSIP pattern is the histological background of a subacute/chronic interstitial pneumonitis that may be observed in many conditions, including CTD, drug-induced lung disease, hypersensitivity pneumonitis, slowly healing diffuse alveolar damage (DAD), relapsing organizing pneumonia, occupational exposure, immunodeficiency (mainly HIV infection), graft versus host disease (GVHD), familial pulmonary fibrosis, immunoglobulin G4 (IgG4)-related sclerosing disease, with or without overlap features with Rosai-Dorfman disease, multicentric Castleman disease, and myelodysplastic syndrome. Rarely, NSIP is the histology recognized in patients with idiopathic interstitial pneumonitis, in whom efforts to find potential causative exposures are futile. This entity occurs mostly in middle-aged, never-smoker women, with a likely association with an autoimmune background. High-resolution computed tomographic (HRCT) scans typically demonstrate ground-glass attenuation with a bibasilar distribution, or in the fibrotic variant, ground-glass attenuation along with reticular lines and traction bronchiectasis. The prognosis is good compared with idiopathic pulmonary fibrosis (IPF), and therapeutic options include mainly corticosteroids and immunosuppressive agents. Recently a more precise definition of clinical profiles and radiographic findings of idiopathic NSIP allows consideration of less invasive diagnostic procedures (bronchoalveolar lavage, transbronchial lung biopsy). Better understanding of pathogenetic mechanisms might widen the therapeutic horizon giving a role to new therapeutic options in more severe cases.
Poletti V
,Romagnoli M
,Piciucchi S
,Chilosi M
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Rare idiopathic interstitial pneumonias: LIP and PPFE and rare histologic patterns of interstitial pneumonias: AFOP and BPIP.
In the 2013 reclassification of the idiopathic interstitial pneumonias (IIPs), two rare IIPs (idiopathic lymphoid interstitial pneumonia (LIP), idiopathic pleuroparenchymal fibroelastosis (IPPFE)) and two rare histologic patterns (acute fibrinous and organizing pneumonia (AFOP), bronchiolocentric pattern of interstitial pneumonia (BPIP)) are described. All these entities are rare with small series published to date, mostly containing primary and secondary forms of disease. LIP is histologically characterized by diffuse polyclonal lymphoid cell infiltrate surrounding the airways and expanding the interstitium. Thin-walled cysts and diffuse ground glass are considered the typical radiologic features. The clinical course is highly variable with corticosteroid responsiveness evident in approximately half of cases. IPPFE is defined histologically by coexisting upper lobe pleural and intra-alveolar fibrosis with elastosis. Dense subpleural irregular fibrosis and consolidation are the cardinal radiologic features. A history of recurrent lower respiratory tract infection is frequent. Responses to immunomodulation have not been reported and the rate of progression appears to be highly variable. AFOP is a rare histologic pattern lying within the spectrum of acute/subacute lung injury, characterized by organizing pneumonia and intra-alveolar fibrin deposition without hyaline membranes. BPIP is characterized histologically by fibrosis and/or inflammation confined to the alveolar interstitium around bronchovascular bundles, overlapping with peribronchial metaplasia and fibrosis in some series. Currently, AFOP and BPIP are both best viewed as histological entities rather than true clinical disorders, in the absence of characteristic associated imaging patterns and clinical features.
Kokosi MA
,Nicholson AG
,Hansell DM
,Wells AU
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