Or 'ILD'. (Fr: PnP subaiguë). A.k.a. pulmonary infiltrates. Generally bilateral and symmetrical. Gradual onset. Consistent with but not specific for an NSIP-c pattern on pathology. Less- dense, severe, acute and diffuse than pattern Ia. Lacks the features of ARDS that may accompany pattern Ia. Can be in the form of disseminated linear, reticulonodular, miliary or patchy opacities. BAL is indicated to separate this pattern from PIE (Ic) or DAH (IIIa). Acute chest pain can be at the forefront. A search for microorganisms including Pneumocystis (stains, PCR) is indicated. On pathology (although not many cases undergo a confirmatory lung biopsy), there is interstitial inflammation and a more or less dense cellular interstitial cellular infiltrate (NSIP-c). Fibrosis, alveolar edema and/or a reactive epithelium denote those cases resulting from with antineoplastic chemotherapy agents. The frontier between patterns Ia and I b can be difficult to draw, so please check drugs under both Ia and Ib. Patients may quickly shift from pattern Ib to Ia particularly if the the causal drug is inappropriately continued. Prompt withdrawal must be considered, underlying disease permitting, and can be therapeutic.