Case report

Acquired immunodeficiency syndrome may present as severe restrictive lung disease

Idiopathic interstitial pneumonias represent an important group of interstitial lung diseases, encompassing seven entities: (1) usual interstitial pneumonia (UIP)/idiopathic pulmonary fibrosis; (2) non-specific interstitial pneumonia (NSIP); (3) organizing pneumonia/cryptogenic organizing pneumonia (COP); (4) diffuse alveolar damage (DAD)/acute interstitial pneumonia (AIP); (5) respiratory bronchiolitis (RB)/respiratory bronchiolitis–interstitial lung disease (RB–ILD); (6) desquamative interstitial pneumonia (DIP); and (7) lymphocytic interstitial pneumonia (LIP). The term idiopathic means that the cause is not certain at the time of diagnosis, but each of these patterns of interstitial pneumonia can occur in the setting of known causes as well.

This review will highlight the pathological features and differential diagnosis of interstitial pneumonias, along with the high-resolution computed tomography (HRCT) scan and clinical features, emphasizing the importance of clinical, radiological and pathological correlation to establish the correct diagnosis. Familiarity with the histological patterns of lung injury in these disorders will aid pathologists in recognizing the correct diagnosis. It is also important for pathologists and clinicians to understand the settings in which HRCT can overrule pathological findings. In particular, if an HRCT scan shows classical features of UIP, despite surgical biopsy findings of NSIP, the clinical–radiological–pathological diagnosis would be UIP.

Lymphocytic interstitial pneumonitis (LIP) and nonspecific interstitial pneumonitis (NIP) are pulmonary complications of human immunodeficiency virus (HIV) infection that occur in the absence of a detectable opportunistic infection or neoplasm. We reviewed lung biopsy specimens from 50 adult HIV-infected patients, of whom four had LIP and 46 had NIP. The majority (47 of 50) of specimens from patients with NIP showed mild chronic interstitial pneumonitis ($\text{CIP}\text{NIP}$), with three showing features of diffuse alveolar damage, organizing phase. In contrast to $\text{CIP}\text{NIP}$, the five specimens from four patients with LIP demonstrated more extensive lymphocytic interstitial infiltrates that extended into the alveolar septal interstitium. The majority of the interstitial lymphocytes in both NIP and LIP were of T-cell origin and stained for UCHL-1. The etiologies of NIP and LIP remain unknown. Since the common opportunistic infections were excluded by routine methods, we sought, with special techniques, to investigate whether HIV, Epstein-Barr virus (EBV), or cytomegalovirus (CMV) could be identified in lung biopsy specimens from these patients. By in situ hybridization, we found one LIP specimen with expression of large amounts of HIV RNA primarily within macrophages in germinal centers; in the remaining specimens, occasional cells expressing HIV RNA were found (two LIP and four NIP). Neither CMV nor EBV was found by in situ hybridization in seven specimens; in these same specimens EBV was detected using the polymerase chain reaction in only one case of NIP, similar to results in control specimens. These results, together with the knowledge that lymphocytic pulmonary lesions may be caused by lentiviruses in humans and animals, suggest that HIV plays a significant role in the pathogenesis of both NIP and LIP in adult HIV-infected patients; in contrast, our data do not demonstrate a direct role for either EBV or CMV.

We retrospectively studied the acute toxicity of corticosteroid therapy in 23 episodes of PCP occurring in the setting of AIDS and determined the incidence of HIV-related complications following these and 16 other contemporaneous episodes of AIDS-related PCP treated with antimicrobials alone. The mean duration of corticosteroid therapy was 5.4 days and the mean total dose was 660 mg of methylprednisolone. Cryptococcus neoformans and Listeria monocytogenes infection each occurred once within one month of therapy in corticosteroid-treated patients; no other noteworthy acute corticosteroid toxicity was noted. Since all patients with imminently lethal PCP received corticosteroids, we could not assess the effect of these agents on acute mortality. After six months the rates of new AIDS-related diagnoses and of post-hospitalization mortality were equivalent in the two groups. We also have critically reviewed the available literature regarding this use of corticosteroids.