Abstract
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.
Keywords
idiopathic nonspecific interstitial pneumonia - clinical classification - high-resolution
CT scan - bronchoalveolar lavage - transbronchial lung biopsy - cyclophosphamide -
rituximab
