Interstitial Lung Disease (ILD)

Diagnostic modalities such as chest X-rays provide static images of the thoracic cavity, including the lungs and airways. While providing a wealth of anatomical information necessary for the diagnosis of pulmonary disease, chest X-rays do not give much information about the individual's respiratory function. Pulmonary function tests are a group of diagnostic procedures yielding useful, quantifiable information about the rate of the flow of air through the individual's airways, lung capacity, and the efficiency of gas exchange in relation to time. The most commonly utilized tests include spirometry (before and after bronchodilator use), lung volumes, and quantitation of diffusing capacity for carbon monoxide (CO). The tests can be influenced by the individual's effort/fatigue, disease state, or anatomical malformation.

Idiopathic pulmonary fibrosis is a specific entity of the major idiopathic interstitial pneumonia classification of interstitial lung diseases. As implied by the name, the exact causes are poorly understood. Patients often present in the moderate to advanced stage with progressive dyspnea and nonproductive cough. The diagnosis is made by characteristic imaging findings, pulmonary function testing that indicates restrictive lung disease, and (if necessary) lung biopsy. Options are limited for therapies to slow progression. Lung transplantation is the only curative intervention if the patient is a candidate for one.

Hypersensitivity pneumonitis (HP), previously called extrinsic allergic alveolitis, is an immunologically induced inflammatory disease affecting the alveoli, bronchioles, and lung parenchyma. It is caused by repeated inhalation of an inciting agent in a susceptible host that triggers first a type III (complement-mediated) hypersensitivity reaction in the acute phase and then a type IV (delayed) reaction in the subacute and chronic phases. The clinical presentation of acute HP includes cough, fever, and malaise, while subacute and chronic forms present as insidious onset of a cough and dyspnea over weeks to months. Diagnosis is aided by high-resolution CT scans and bronchoalveolar lavage. Management includes avoiding the inciting agent and administration of steroids in subacute and chronic cases. Early treatment has a good prognosis, but long-term exposure can cause permanent scarring and fibrosis.

Sarcoidosis is a multisystem inflammatory disease that causes noncaseating granulomas. The exact etiology is unknown. Sarcoidosis usually affects the lungs and thoracic lymph nodes, but it can also affect almost every system in the body, including the skin, heart, and eyes, most commonly. Acutely, sarcoidosis presents with lymphadenopathy, fever, malaise, joint pains, a panniculitis on the shins known as erythema nodosum, and occasionally cough and shortness of breath. Chronic pulmonary sarcoidosis presents with an insidious onset of dyspnea, cough, chest pain, and a variety of other symptoms depending on the organ systems involved. Diagnosis often requires a biopsy of the granulomas. Management includes observation, NSAIDs, glucocorticoids, and potentially one of several steroid-sparing agents. Acute sarcoidosis is usually self-limiting with an excellent prognosis, but chronic sarcoidosis can lead to severe pulmonary fibrosis.

Pneumoconiosis is an occupational disease that results from the inhalation and deposition of mineral dusts and other inorganic particles in the lung. It can be categorized according to the type of causative particle involved or by the type of response provoked. Coal, silica, asbestos, and talc are the classic fibrogenic types, while beryllium provokes a granulomatous response, and cobalt is associated with giant cell pneumonia. Iron, tin, and barium are considered benign or inert particle types because they do not cause the same type of reactions as the others. After exposure to the fibrogenic types of particles, macrophages and fibroblasts become activated within the pulmonary parenchyma leading to chronic inflammation and fibrosis, which can progress to respiratory failure and death. Occupational history and chest X-rays are the mainstays of diagnosis and staging. Management is mainly symptomatic.

Interstitial lung diseases are a heterogeneous group of disorders characterized by the inflammation and fibrosis of lung parenchyma, especially the pulmonary connective tissue in the alveolar walls. It may be idiopathic (e.g., idiopathic pulmonary fibrosis) or secondary to connective tissue diseases, medications, malignancies, occupational exposure, or allergens. Interstitial lung diseases commonly present with progressive exertional dyspnea and dry cough. Pulmonary function testing shows a restrictive lung disease pattern. Lung high-resolution computed tomography and biopsy usually establish the diagnosis. Treatment includes steroids and immunosuppressives.