The hospitalized patient with interstitial lung disease: a hospitalist primer

Interstitial lung disease (ILD) encompasses a diverse group of disorders that cause inflammation and fibrosis of the lung parenchyma. The clinical manifestations, disease course, management and prognosis of ILD vary depending on the underlying subtype, making accurate classification and diagnosis an important initial step. While a comprehensive list of ILD contains dozens of disorders, the majority of patients will fall into 1 of 3 categories: exposure-related ILD, connective tissue disease-related ILD (CT-ILD), and the idiopathic interstitial pneumonias (Table).

An essential first step in the evaluation of every hospitalized patient with ILD is establishing a diagnosis. A common mistake among clinicians who diagnose patients with ILD is not realizing that ILD is a collection of diseases with different etiologies, natural histories, and treatments. A careful evaluation should be performed in every hospitalized patient with ILD to ensure an accurate diagnosis, ideally in the context of a multidisciplinary conference with pulmonary, radiology, pathology, and other specialties, as appropriate. A multidisciplinary panel of the American Thoracic Society/European Respiratory Society recently published a revised classification of ILD based on a combination of clinical, radiologic, and histopathologic findings, which may aid in refining the diagnosis.¹

There are 3 main scenarios in which the hospital physician will encounter patients with ILD.

Acute presentation of new-onset disease. While many ILDs present insidiously, some cases present acutely and require hospitalization. The most common of these are acute hypersensitivity pneumonitis (HP), CT-ILD (in particular, myositis-related and systemic lupus erythematosus-related), drug-induced ILD (eg, amiodarone, nitrofurantoin), cryptogenic organizing pneumonia (COP), acute eosinophilic pneumonia (AEP), and acute interstitial pneumonia (AIP).

Acute presentation of established (chronic) disease. Patients with chronic forms of ILD can present to the hospital with an acute exacerbation of disease. This can be caused by extra-parenchymal complications, including pulmonary embolism, pneumothorax, and pleural effusion; parenchymal complications such as infectious pneumonia, aspiration pneumonitis, and congestive heart failure; or without an identifiable cause. This latter presentation is most commonly seen in idiopathic pulmonary fibrosis (IPF).^2,3

Elective hospitalization for diagnostic surgical lung biopsy. Patients with ILD may be hospitalized electively for a laparoscopic surgical lung biopsy as part of their diagnostic evaluations.

Physicians caring for a hospitalized ILD patient must be familiar with the clinical presentations, diagnostic approach, medical management, and outpatient follow-up recommended in these 3 settings. We will summarize these areas and provide answers to commonly encountered clinical questions in the hospitalized patient with ILD.

Acute onset (or worsening) of dyspnea is the primary presenting symptom in most patients hospitalized for ILD. This symptom should be further characterized by assessing the degree of dyspnea and the extent of exercise limitation, as both impact overall disease severity and prognosis.⁴ Cough is the second most common symptom, and can be nonproductive, as is common in IPF, or be associated with secretions if parenchymal infection or acute bronchitis is present.⁵ Pleuritic chest pain, pleural effusion, and/or the presence of extrapulmonary features, including dysphagia, joint pain and swelling, or cutaneous thickening may suggest the presence of a CT-ILD. Because most forms of ILD present with only nonspecific symptoms, a careful history and physical examination are essential.

History

A comprehensive patient history is the backbone of diagnosing any ILD. History-taking should focus on severity and temporal progression of symptoms, presence of pre-existing systemic conditions associated with ILD, symptoms of extrapulmonary disease, and exposures to substances that can cause pulmonary injury, including a detailed history of occupations and hobbies, medications, smoking, and familial lung disease.^6-9 Physicians must try to exclude other diagnoses that could result in a similar acute presentation, including congestive heart failure and infection. Considering the complex and extensive recommended history-taking, physicians may find it helpful to use a standardized questionnaire, as provided by the American College of Chest Physicians.¹⁰