Drug-induced interstitial lung disease

Amiodarone is an iodine-rich class III multichannel antiarrhythmic used for ventricular fibrillation and pulseless ventricular tachycardia in cardiac arrest, sustained ventricular tachycardia, and atrial fibrillation rhythm or rate control when other agents are unsafe. First-line arrest dosing is a 300 mg intravenous push, and long-term use requires monitoring for thyroid, liver, lung, and eye toxicity.

Immune checkpoint inhibitor toxicity is the set of autoimmune-like immune-related adverse events (irAEs) that follow blockade of CTLA-4, PD-1, or PD-L1, most often colitis, hepatitis, pneumonitis, dermatitis, and endocrinopathy. Diagnosis relies on excluding infection and grading severity; first-line treatment for grade 2 or higher toxicity is oral or intravenous corticosteroids with the checkpoint inhibitor held or permanently stopped.

Hodgkin lymphoma is a B-cell malignancy defined by Reed-Sternberg cells that classically presents with painless, contiguously spreading cervical or mediastinal lymphadenopathy in a young adult, and it is confirmed by excisional lymph node biopsy. Ann Arbor/Lugano stage and interim PET response drive risk-adapted ABVD chemotherapy with or without radiation, and most patients are cured.

Interstitial lung disease (ILD), also called diffuse parenchymal lung disease, is a diverse group of nonmalignant disorders causing inflammation and scarring of the alveolar interstitium, presenting as subacute to chronic exertional dyspnea and nonproductive cough. Diagnosis rests on pulmonary function testing plus high-resolution CT pattern recognition; management is exposure removal, glucocorticoids for inflammatory disease, antifibrotic therapy for progressive fibrotic disease, oxygen for hypoxemia, and early transplant referral.

Idiopathic pulmonary fibrosis is a chronic, progressive fibrosing lung disease of unknown cause defined by a usual interstitial pneumonia (UIP) pattern, presenting with progressive dyspnea, dry cough, bibasilar Velcro crackles, and clubbing in older smokers. A definite UIP pattern on high-resolution CT confirms the diagnosis without biopsy; management centers on antifibrotic therapy (pirfenidone or nintedanib), oxygen, and early lung transplant referral, since corticosteroids are not indicated and median survival is 3 to 5 years.

Hypersensitivity pneumonitis is a mixed type III/IV immune reaction to repeated inhalation of an organic antigen in a sensitized host, producing noncaseating granulomas and bronchiolocentric inflammation. Removal of the offending antigen is the essential first step in treatment; glucocorticoids are added for significant hypoxemia or symptom burden, and unremitting exposure can progress to fibrotic lung disease indistinguishable from idiopathic pulmonary fibrosis.

Eosinophilic pneumonia is eosinophil-driven lung injury presenting as two distinct syndromes, acute eosinophilic pneumonia causing rapid hypoxemic respiratory failure and chronic eosinophilic pneumonia causing weeks to months of relapsing symptoms, both confirmed by bronchoalveolar lavage eosinophilia and both dramatically responsive to corticosteroids.

Sarcoidosis is a multisystem granulomatous disease of unknown cause defined by noncaseating granulomas, most commonly involving the lungs and hilar lymph nodes. Most patients are asymptomatic or have a self-limited course staged by chest radiograph; symptomatic organ-threatening disease is treated with systemic glucocorticoids, with methotrexate or another steroid-sparing agent added for glucocorticoid-refractory or glucocorticoid-intolerant disease.

Radiation therapy toxicity is organ injury from therapeutic ionizing radiation given for cancer, split into acute toxicities from direct cytotoxic injury during treatment and late toxicities from progressive fibrosis appearing months to decades later in the treated field. Diagnosis correlates symptom timing and imaging pattern with the radiation field after excluding recurrence and infection; management is organ-specific and supportive, plus lifelong surveillance for secondary malignancy.

ARDS is acute (within 1 week), bilateral, non-cardiogenic hypoxemic respiratory failure from diffuse alveolar damage, diagnosed by the 2012 Berlin criteria and graded by the Pao2/Fio2 ratio. Management is lung-protective ventilation, PEEP titration, early prone positioning for severe disease, conservative fluid strategy, and treatment of the inciting insult.

Pneumocystis jirovecii pneumonia is a subacute, often hypoxic pneumonia in patients with CD4 counts below 200/mcL or comparable immunosuppression, diagnosed by organism visualization on induced sputum or bronchoalveolar lavage and treated with 21 days of high-dose trimethoprim-sulfamethoxazole plus adjunctive steroids when hypoxic.

Connective tissue disease-associated interstitial lung disease (CTD-ILD) is parenchymal lung fibrosis or inflammation driven by an underlying rheumatologic disease, with the causative disease and its serology dictating the radiographic pattern and treatment. Diagnosis proceeds from HRCT pattern to a directed autoantibody panel, since unlike idiopathic pulmonary fibrosis, most CTD-ILD is treated with immunosuppression.

Rheumatoid arthritis is a chronic systemic autoimmune disease causing symmetric small-joint polyarthritis of the hands and feet that spares the distal interphalangeal joints, with morning stiffness over an hour. Diagnosis combines the ACR/EULAR classification criteria with rheumatoid factor, anti-CCP antibody, and radiographs. Treat-to-target management anchors on methotrexate, escalating to a biologic or targeted synthetic disease-modifying antirheumatic drug when remission is not reached.