Abstract and Introduction
Abstract
Drug-induced interstitial lung disease (DILD) is not uncommon and has many clinical patterns, ranging from benign infiltrates to life-threatening acute respiratory distress syndrome. There are two mechanisms involved in DILD, which are probably interdependent: one is direct, dose-dependent toxicity and the other is immune-mediated. Cytotoxic lung injury may result from direct injury to pneumocytes or the alveolar capillary endothelium. Drugs can induce all types of immunological reactions described by Gell and Coombs; however, most reactions in immune-mediated DILD may be T cell-mediated.
DILD can be difficult to diagnose; diagnosis is often possible by exclusion alone. Identifying the causative drug that induces an allergy or cytotoxicity is essential for preventing secondary reactions.
One method to confirm the diagnosis of a drug-induced disease is re-exposure or re-test of the drug. However, clinicians are reluctant to place patients at further risk of illness, particularly in cases with severe drug-induced diseases. Assessment of cell-mediated immunity has recently increased, because verifying the presence or absence of drug-sensitized lymphocytes can aid in confirmation of drug-induced disease. Using peripheral blood samples from drug-allergic patients, the drug-induced lymphocyte stimulation test (DLST) and the leukocyte migration test (LMT) can detect the presence of drug-sensitized T cells. However, these tests do not have a definite role in the diagnosis of DILD. This study explores the potential of these new tests and other similar tests in the diagnosis of DILD and provides a review of the relevant literature on this topic.
Introduction
Several types of drugs can cause drug-induced interstitial lung disease (DILD). The incidence of DILD for each individual drug is variable. DILD may be mild to progressive. In its more severe manifestation, DILD may result in respiratory failure and acute respiratory distress syndrome. DILD may develop within the first few days of treatment or may not until several years after treatment. DILD is generally described in terms of its clinical/histopathological features. The mechanisms involved in drug-induced lung injuries are unclear; therefore, DILD cannot be classified in terms of pathogenesis.
Diagnosis of DILD generally depends on a definite temporal association between an exposure to the causative agent and the development of respiratory signs and symptoms. The most important for accurate diagnosis is the exclusion of other causes of lung damage. Specific markers, histological findings, and diagnostic clinical features are generally unremarkable in DILD. Difficulties arise when signs and symptoms develop after the drug is discontinued rather than during treatment or when no improvement follows discontinuation of the drug. Making a timely and accurate diagnosis of DILD is very important to ensure a favorable outcome.