ABSTRACT
Interstitial lung diseases encompass a heterogeneous group of disease processes
characterized by a variety of clinical, radiographical, and histopathological mani-
festations. The term ‘‘diffuse parenchymal lung diseases’’ may be preferred as it
reflects more accurately the wide range of changes that can be observed histolog-
ically. Considerable efforts have been made to develop a coherent and organized
classification of these disorders, but as our understanding of the various pathogenic
mechanisms broadens, more unanswered questions appear both for clinicians and
their patients. A new diagnosis of diffuse parenchymal lung disease triggers a
battery of laboratory, microbiological, and histological investigations, which
sometimes point to a defined etiological agent that can guide therapy. In virtually all
cases of diffuse parenchymal lung disease, the possibility of drug-induced pulmo-
nary toxicity should be systematically entertained and appropriate history obtained
from the patient, including not only prescription medications, but also over-the-
counter and herbal medications. This may represent a time-consuming task for the
clinician as these histories are notoriously incomplete or unreliable, and as the use of
some agents, such as illicit drugs, may not be easily volunteered. It is, however, a
crucial step in the evaluation of a patient as it may preclude other onerous and
lengthy investigations, and will lead to necessary therapeutic measures including
discontinuation of the drug, and occasionally, the administration of corticosteroids.
