Interstitial Lung Diseases

Interstitial lung diseases are a heterogeneous group of disorders characterized by the inflammation Inflammation Inflammation is a complex set of responses to infection and injury involving leukocytes as the principal cellular mediators in the body's defense against pathogenic organisms. Inflammation is also seen as a response to tissue injury in the process of wound healing. The 5 cardinal signs of inflammation are pain, heat, redness, swelling, and loss of function. Inflammation and fibrosis of lung parenchyma, especially the pulmonary connective tissue Connective tissue Connective tissues originate from embryonic mesenchyme and are present throughout the body except inside the brain and spinal cord. The main function of connective tissues is to provide structural support to organs. Connective tissues consist of cells and an extracellular matrix. Connective Tissue in the alveolar walls. It may be idiopathic (e.g., idiopathic pulmonary fibrosis Pulmonary Fibrosis 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. Pulmonary Fibrosis) or secondary to connective tissue Connective tissue Connective tissues originate from embryonic mesenchyme and are present throughout the body except inside the brain and spinal cord. The main function of connective tissues is to provide structural support to organs. Connective tissues consist of cells and an extracellular matrix. Connective Tissue diseases, medications, malignancies, occupational exposure, or allergens. Interstitial lung diseases commonly present with progressive exertional dyspnea Dyspnea Dyspnea is the subjective sensation of breathing discomfort. Dyspnea is a normal manifestation of heavy physical or psychological exertion, but also may be caused by underlying conditions (both pulmonary and extrapulmonary). 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.

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Overview

Definition

  • Interstitial lung disease (ILD) comprises a heterogeneous group of disorders that cause varying degrees of inflammation Inflammation Inflammation is a complex set of responses to infection and injury involving leukocytes as the principal cellular mediators in the body's defense against pathogenic organisms. Inflammation is also seen as a response to tissue injury in the process of wound healing. The 5 cardinal signs of inflammation are pain, heat, redness, swelling, and loss of function. Inflammation and fibrosis of the lung interstitium, the space between the capillary endothelium and the alveolar epithelium Epithelium The epithelium is a complex of specialized cellular organizations arranged into sheets and lining cavities and covering the surfaces of the body. The cells exhibit polarity, having an apical and a basal pole. Structures important for the epithelial integrity and function involve the basement membrane, the semipermeable sheet on which the cells rest, and interdigitations, as well as cellular junctions. Surface Epithelium.
  • Clinically, affected patients will show restrictive lung disease by pulmonary function studies.

Epidemiology

Idiopathic pulmonary fibrosis Pulmonary Fibrosis 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. Pulmonary Fibrosis, sarcoidosis Sarcoidosis 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. Sarcoidosis, and ILD associated with connective tissue Connective tissue Connective tissues originate from embryonic mesenchyme and are present throughout the body except inside the brain and spinal cord. The main function of connective tissues is to provide structural support to organs. Connective tissues consist of cells and an extracellular matrix. Connective Tissue diseases are the most common types of ILD.

Classification

It is useful to categorize ILDs into those with and without a known cause.

Table: Types of interstitial lung disease
Cause unknown Cause known
Idiopathic interstitial pneumonias (IIP):
  • Idiopathic pulmonary fibrosis Pulmonary Fibrosis 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. Pulmonary Fibrosis (IPF)
  • Nonspecific interstitial pneumonia Pneumonia Pneumonia or pulmonary inflammation is an acute or chronic inflammation of lung tissue. Causes include infection with bacteria, viruses, or fungi. In more rare cases, pneumonia can also be caused through toxic triggers through inhalation of toxic substances, immunological processes, or in the course of radiotherapy. Pneumonia (NSIP)
  • Cryptogenic organizing pneumonia Pneumonia Pneumonia or pulmonary inflammation is an acute or chronic inflammation of lung tissue. Causes include infection with bacteria, viruses, or fungi. In more rare cases, pneumonia can also be caused through toxic triggers through inhalation of toxic substances, immunological processes, or in the course of radiotherapy. Pneumonia (COP)
  • Acute interstitial pneumonia Pneumonia Pneumonia or pulmonary inflammation is an acute or chronic inflammation of lung tissue. Causes include infection with bacteria, viruses, or fungi. In more rare cases, pneumonia can also be caused through toxic triggers through inhalation of toxic substances, immunological processes, or in the course of radiotherapy. Pneumonia (AIP)
Smoking-related ILD:
  • Respiratory bronchiolitis-associated interstitial pneumonia Pneumonia Pneumonia or pulmonary inflammation is an acute or chronic inflammation of lung tissue. Causes include infection with bacteria, viruses, or fungi. In more rare cases, pneumonia can also be caused through toxic triggers through inhalation of toxic substances, immunological processes, or in the course of radiotherapy. Pneumonia (RB-AIP)
  • Desquamative interstitial pneumonia Pneumonia Pneumonia or pulmonary inflammation is an acute or chronic inflammation of lung tissue. Causes include infection with bacteria, viruses, or fungi. In more rare cases, pneumonia can also be caused through toxic triggers through inhalation of toxic substances, immunological processes, or in the course of radiotherapy. Pneumonia (DIP)
Other:
  • Lymphangioleiomyomatosis (LAM)
Systemic diseases
  • Connective tissue diseases (CTD)
    • Rheumatoid arthritis Rheumatoid arthritis Rheumatoid arthritis (RA) is a symmetric, inflammatory polyarthritis and chronic, progressive, autoimmune disorder. Presentation occurs most commonly in middle-aged women with joint swelling, pain, and morning stiffness (often in the hands). Rheumatoid Arthritis (RA)
    • Systemic lupus erythematosus Systemic lupus erythematosus Systemic lupus erythematosus (SLE) is a chronic autoimmune, inflammatory condition that causes immune-complex deposition in organs, resulting in systemic manifestations. Women, particularly those of African American descent, are more commonly affected. Systemic Lupus Erythematosus
    • Systemic sclerosis Systemic sclerosis Scleroderma (systemic sclerosis) is an autoimmune condition characterized by diffuse collagen deposition and fibrosis. The clinical presentation varies from limited skin involvement to diffuse involvement of internal organs. Scleroderma
    • Sjogren’s disease
    • Dermatomyositis/ polymyositis Polymyositis Polymyositis (PM) is an autoimmune inflammatory myopathy caused by T cell-mediated muscle injury. The etiology of PM is unclear, but there are several genetic and environmental associations. Polymyositis is most common in middle-aged women and rarely affects children. Polymyositis
  • Granulomatous disease
    • Granulomatosis with polyangiitis Granulomatosis with Polyangiitis Granulomatosis with polyangiitis (GPA) is a rare autoimmune disease of unknown etiology. It leads to a necrotizing granulomatous inflammation of small and medium-sized blood vessels of the nose, sinuses, throat, lungs, and kidneys. Granulomatosis with Polyangiitis
    • Churg-Strauss disease
    • Pulmonary Langerhans cell histiocytosis (PLCH)
    • Sarcoidosis
    • Hypersensitivity pneumonitis Hypersensitivity Pneumonitis 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. Hypersensitivity Pneumonitis (HP)
Exposure-related
  • Occupational
    • Asbestosis
    • Silicosis
    • Gases/fumes
  • Pharmacologic:
    Radiation, methotrexate, azathioprine, rituximab, tumor-necrosis factor blockers, amiodarone, nitrofurantoin, chemotherapeutics

Diagnosis

History

Age
  • IPF is rare in patients < 50 years
  • Sarcoidosis, CTD-associated ILD, and LAM are common between the ages of 20 and 40 years
Sex
  • LAM and CTD-associated ILD, except rheumatoid arthritis-associated ILD, are frequently found in women
  • IPF and occupational ILDs are more common in men
Clinical presentation
  • Acute onset (days to weeks): eosinophilic pneumonia Pneumonia Pneumonia or pulmonary inflammation is an acute or chronic inflammation of lung tissue. Causes include infection with bacteria, viruses, or fungi. In more rare cases, pneumonia can also be caused through toxic triggers through inhalation of toxic substances, immunological processes, or in the course of radiotherapy. Pneumonia, acute interstitial pneumonia Pneumonia Pneumonia or pulmonary inflammation is an acute or chronic inflammation of lung tissue. Causes include infection with bacteria, viruses, or fungi. In more rare cases, pneumonia can also be caused through toxic triggers through inhalation of toxic substances, immunological processes, or in the course of radiotherapy. Pneumonia, hypersensitivity pneumonitis, granulomatosis with polyangiitis, acute exacerbation of IPF
  • Subacute onset (weeks to months) and especially chronic onset (months to years): most other ILDs, especially IPF
Symptoms
  • Progressive exertional dyspnea Dyspnea Dyspnea is the subjective sensation of breathing discomfort. Dyspnea is a normal manifestation of heavy physical or psychological exertion, but also may be caused by underlying conditions (both pulmonary and extrapulmonary). Dyspnea (most common)
  • Dry cough (very common)
  • Fatigue (common)
  • Chest pain Chest Pain Chest pain is one of the most common and challenging complaints that may present in an inpatient and outpatient setting. The differential diagnosis of chest pain is large and includes cardiac, gastrointestinal, pulmonary, musculoskeletal, and psychiatric etiologies. Chest Pain (uncommon; suggests sarcoidosis Sarcoidosis 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. Sarcoidosis)
  • Hemoptysis Hemoptysis Hemoptysis is defined as the expectoration of blood originating in the lower respiratory tract. Hemoptysis is a consequence of another disease process and can be classified as either life threatening or non-life threatening. Hemoptysis can result in significant morbidity and mortality due to both drowning (reduced gas exchange as the lungs fill with blood) and hemorrhagic shock. Hemoptysis (rare; suggests vasculitis, LAM)
Past medical history
  • CTD or symptoms of CTD such as Raynaud’s phenomena
  • Malignancy, which may indicate dermatomyositis-associated ILD
  • Asthma Asthma Asthma is a chronic inflammatory respiratory condition characterized by bronchial hyperresponsiveness and airflow obstruction. The disease is believed to result from the complex interaction of host and environmental factors that increase disease predisposition, with inflammation causing symptoms and structural changes. Patients typically present with wheezing, cough, and dyspnea. Asthma may suggest eosinophilic granulomatosis with polyangiitis (also known as Churg-Strauss)
Drug history Methotrexate, azathioprine, rituximab, tumor-necrosis factor blockers, amiodarone, nitrofurantoin, chemotherapeutics
Family history Having a close relative with IIP is a strong risk factor for ILD, especially IPF.
Social history
  • Smoking history is present in almost all cases of DIP and the majority of IPF patients.
  • Exposure history such as to asbestos or birds (HP)

Physical examination

  • End-inspiratory fine crackles in lung bases (common finding, especially in IPF)
  • Wheezing Wheezing Wheezing is an abnormal breath sound characterized by a whistling noise that can be relatively high-pitched and shrill (more common) or coarse. Wheezing is produced by the movement of air through narrowed or compressed small (intrathoracic) airways. Wheezing is uncommon (may be found in HP, Churg-Strauss disease, sarcoidosis Sarcoidosis 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. Sarcoidosis)
  • Severe disease findings: cyanosis, digital clubbing, cor pulmonale Cor Pulmonale Cor pulmonale is right ventricular (RV) dysfunction caused by lung disease that results in pulmonary artery hypertension. The most common cause of cor pulmonale is chronic obstructive pulmonary disease. Dyspnea is the usual presenting symptom. Cor Pulmonale

Laboratory studies

Autoantibody detection may help with the diagnosis of some CTDs.

Pulmonary function testing

  • The diffusing capacity for carbon monoxide (DLCO) shows reduction.
  • Most show a restrictive pattern.

Imaging

  • Chest X-ray may be suggestive of a type of ILD:
    • Peripheral reticular pattern in lower lung zones and small cystic spaces suggests IPF.
    • Central nodular pattern in mid-to-upper lung zones and hilar lymph node enlargement suggests sarcoidosis Sarcoidosis 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. Sarcoidosis.
  • Chest computed tomography (CT):
    • Standard initial test
    • May confirm the diagnosis of IPF in the right setting and obviate the need for lung biopsy
    • Better defines disease extent and features (e.g., honeycombing)
    • Helps exclude comorbidities (e.g., pneumothorax Pneumothorax A pneumothorax is a life-threatening condition in which air collects in the pleural space, causing partial or full collapse of the lung. A pneumothorax can be traumatic or spontaneous. Patients present with a sudden onset of sharp chest pain, dyspnea, and diminished breath sounds on exam. Pneumothorax) or differential diagnosis (e.g., malignancy)
    • Helps determine the best location for biopsy

Lung biopsy

  • Establishes the diagnosis
  • Performed via fiberoptic bronchoscopy or surgery
  • Biopsy is not needed if:
    • High-resolution CT (HRCT) shows classic usual interstitial pneumonia Pneumonia Pneumonia or pulmonary inflammation is an acute or chronic inflammation of lung tissue. Causes include infection with bacteria, viruses, or fungi. In more rare cases, pneumonia can also be caused through toxic triggers through inhalation of toxic substances, immunological processes, or in the course of radiotherapy. Pneumonia and the patient has no systemic diseases suggestive of an another disorder.
    • Patient has minimal signs or symptoms and a stable/nonprogressive disease.
  • Indicated in cases of comorbidities or rapidly progressive symptoms

Individual Forms

Idiopathic pulmonary fibrosis Pulmonary Fibrosis 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. Pulmonary Fibrosis

  • Most common ILD of unknown cause
  • Commonly diagnosed in 5th or 6th decade
  • Affects men more than women
  • Frequently associated with smoking
  • 35-year survival rate is 50%.
  • May be associated with acute exacerbations
  • Lung HRCT shows a pattern of UIP: subpleural reticular pattern with posterior-basal predominance with more advanced fibrotic features such as honeycombing and traction bronchiectasis Bronchiectasis Bronchiectasis is a chronic disease of the airways that results from permanent bronchial distortion. This results from a continuous cycle of inflammation, bronchial damage and dilation, impaired clearance of secretions, and recurrent infections. Bronchiectasis.
  • Histopathology shows a pattern of UIP: subpleural reticulation, honeycombing, fibroblasts, skipped lesions with preserved architecture (temporal and spatial heterogeneity).
  • Treatment: physical therapy and supplemental oxygen, antifibrotic therapy (pirfenidone), and lung transplantation if patient meets criteria

Non-specific interstitial pneumonia Pneumonia Pneumonia or pulmonary inflammation is an acute or chronic inflammation of lung tissue. Causes include infection with bacteria, viruses, or fungi. In more rare cases, pneumonia can also be caused through toxic triggers through inhalation of toxic substances, immunological processes, or in the course of radiotherapy. Pneumonia

  • May be idiopathic or commonly associated with CTDs
  • Commonly diagnosed in non-smoking women in their 5th decade
  • 5-year survival rate is 80%.
  • Lung HRCT shows diffuse and symmetric subpleural ground-glass and reticular opacities; traction bronchiectasis Bronchiectasis Bronchiectasis is a chronic disease of the airways that results from permanent bronchial distortion. This results from a continuous cycle of inflammation, bronchial damage and dilation, impaired clearance of secretions, and recurrent infections. Bronchiectasis may be seen; honeycombing and peribronchial thickening is uncommon.
  • Histopathology shows uniform interstitial inflammation Inflammation Inflammation is a complex set of responses to infection and injury involving leukocytes as the principal cellular mediators in the body's defense against pathogenic organisms. Inflammation is also seen as a response to tissue injury in the process of wound healing. The 5 cardinal signs of inflammation are pain, heat, redness, swelling, and loss of function. Inflammation and fibrosis without honeycombing.
  • Treatment: physical therapy, supplemental oxygen, steroids, immunosuppressive therapy, and lung transplantation if patient meets criteria

Cryptogenic organizing pneumonia Pneumonia Pneumonia or pulmonary inflammation is an acute or chronic inflammation of lung tissue. Causes include infection with bacteria, viruses, or fungi. In more rare cases, pneumonia can also be caused through toxic triggers through inhalation of toxic substances, immunological processes, or in the course of radiotherapy. Pneumonia

  • May be idiopathic or secondary to polymyositis Polymyositis Polymyositis (PM) is an autoimmune inflammatory myopathy caused by T cell-mediated muscle injury. The etiology of PM is unclear, but there are several genetic and environmental associations. Polymyositis is most common in middle-aged women and rarely affects children. Polymyositis, medications, or malignancy
  • Commonly diagnosed in 6th or 7th decade
  • Lung HRCT shows migratory, patchy, subpleural consolidations and ground-glass opacities with or without a rim of subpleural sparing known as the halo sign (characteristic).
  • Treatment: steroids and immunosuppressives

Smoking-related ILD

  • Occurs in heavy smokers in the 5th or 6th decade
  • Honeycombing is typically absent
  • Biopsy confirms diagnosis
  • Treatment includes smoking cessation and immunosuppressive therapy

Connective tissue disease–associated ILD and granulomatous ILD

Table: Typical features of systemic sclerosis (a common cause of CTD–associated ILD), sarcoidosis Sarcoidosis 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. Sarcoidosis (most common granulomatous ILD), and IPF (most common idiopathic ILD)
IPF Systemic sclerosis Systemic sclerosis Scleroderma (systemic sclerosis) is an autoimmune condition characterized by diffuse collagen deposition and fibrosis. The clinical presentation varies from limited skin involvement to diffuse involvement of internal organs. Scleroderma–associated ILD Sarcoidosis
Symptoms Older adult with gradual shortness of breath and dry cough Gradual shortness of breath and dry cough, fatigue, skin Skin The skin, also referred to as the integumentary system, is the largest organ of the body. The skin is primarily composed of the epidermis (outer layer) and dermis (deep layer). The epidermis is primarily composed of keratinocytes that undergo rapid turnover, while the dermis contains dense layers of connective tissue. Structure and Function of the Skin tightening, Raynaud’s phenomenon, reflux, dysphagia Dysphagia Dysphagia is the subjective sensation of difficulty swallowing. Symptoms can range from a complete inability to swallow, to the sensation of solids or liquids becoming "stuck." Dysphagia is classified as either oropharyngeal or esophageal, with esophageal dysphagia having 2 sub-types: functional and mechanical. Dysphagia Asymptomatic or with gradual shortness of breath and cough, fatigue, palpitations, joint pain Pain Pain has accompanied humans since they first existed, first lamented as the curse of existence and later understood as an adaptive mechanism that ensures survival. Pain is the most common symptomatic complaint and the main reason why people seek medical care. Physiology of Pain, eye and skin Skin The skin, also referred to as the integumentary system, is the largest organ of the body. The skin is primarily composed of the epidermis (outer layer) and dermis (deep layer). The epidermis is primarily composed of keratinocytes that undergo rapid turnover, while the dermis contains dense layers of connective tissue. Structure and Function of the Skin involvement
Signs Crackles at lung bases and digital clubbing Crackles, skin Skin The skin, also referred to as the integumentary system, is the largest organ of the body. The skin is primarily composed of the epidermis (outer layer) and dermis (deep layer). The epidermis is primarily composed of keratinocytes that undergo rapid turnover, while the dermis contains dense layers of connective tissue. Structure and Function of the Skin thickening and joint swelling, telangiectasias None or crackles, skin Skin The skin, also referred to as the integumentary system, is the largest organ of the body. The skin is primarily composed of the epidermis (outer layer) and dermis (deep layer). The epidermis is primarily composed of keratinocytes that undergo rapid turnover, while the dermis contains dense layers of connective tissue. Structure and Function of the Skin findings, joint swelling, lymphadenopathy Lymphadenopathy Lymphadenopathy is lymph node enlargement (> 1 cm) and is benign and self-limited in most patients. Etiologies include malignancy, infection, and autoimmune disorders, as well as iatrogenic causes such as the use of certain medications. Generalized lymphadenopathy often indicates underlying systemic disease. Lymphadenopathy
Exposures Tobacco smoke Mostly unknown Mostly unknown
HRCT
  • Bilateral peripheral reticular pattern in lower posterior lung zones
  • Honeycombing
  • Tractional bronchiectasis Bronchiectasis Bronchiectasis is a chronic disease of the airways that results from permanent bronchial distortion. This results from a continuous cycle of inflammation, bronchial damage and dilation, impaired clearance of secretions, and recurrent infections. Bronchiectasis
  • UIP pattern is diagnostic.
UIP or NSIP pattern, dilated esophagus Esophagus The esophagus is a muscular tube-shaped organ of around 25 centimeters in length that connects the pharynx to the stomach. The organ extends from approximately the 6th cervical vertebra to the 11th thoracic vertebra and can be divided grossly into 3 parts: the cervical part, the thoracic part, and the abdominal part. Esophagus, pulmonary vascular dilation Mediastinal/hilar lymphadenopathy Lymphadenopathy Lymphadenopathy is lymph node enlargement (> 1 cm) and is benign and self-limited in most patients. Etiologies include malignancy, infection, and autoimmune disorders, as well as iatrogenic causes such as the use of certain medications. Generalized lymphadenopathy often indicates underlying systemic disease. Lymphadenopathy, reticulonodular peribronchiovascular involvement
Histopathology UIP pattern (fibroblastic foci, honeycombing, spatial heterogeneity) NSIP pattern with occasional UIP features Non-caseating granuloma
Clinical course 3–5 year survival: 50% 10-year survival: 70%–80% Overall good survival

Complications

  • Acute exacerbations of IIPs:
    • Accelerated phase of lung injury in a patient with an underlying ILD
    • Acute onset (< 30 days) of respiratory distress and hypoxemia more severe than what was previously experienced by the underlying ILD and not explained by other causes (e.g., pneumonia Pneumonia Pneumonia or pulmonary inflammation is an acute or chronic inflammation of lung tissue. Causes include infection with bacteria, viruses, or fungi. In more rare cases, pneumonia can also be caused through toxic triggers through inhalation of toxic substances, immunological processes, or in the course of radiotherapy. Pneumonia, heart failure)
    • Most commonly described in IPF
    • Lung HRCT shows a change in the pattern previously observed due to the underlying ILD with patchy bilateral ground-glass opacities and consolidation in dependent regions.
    • Histopathology shows diffuse alveolar damage.
    • Treatment is supportive as no proven therapy exists; lung transplantation may provide cure.
    • Mortality rate > 85%
  • Pulmonary hypertension Pulmonary Hypertension Pulmonary hypertension (PH) or pulmonary arterial hypertension (PAH) is characterized by elevated pulmonary arterial pressure, which can lead to chronic progressive right heart failure. Pulmonary hypertension is grouped into 5 categories based on etiology, which include primary PAH, and PH due to cardiac disease, lung or hypoxic disease, chronic thromboembolic disease, and multifactorial or unclear etiologies. Pulmonary Hypertension
  • Pneumonia
  • Ischemic heart disease Ischemic heart disease Coronary heart disease (CHD), or ischemic heart disease, describes a situation in which an inadequate supply of blood to the myocardium exists due to a stenosis of the coronary arteries, typically from atherosclerosis. Coronary Heart Disease
  • Thromboembolic disease
  • Lung cancer

Differential Diagnosis

  • Cardiovascular disease (e.g., heart failure)
  • Diffuse infections (e.g., pneumocystis pneumonia Pneumocystis Pneumonia Pneumocystis jiroveci is a yeast-like fungus causing pneumocystis pneumonia (PCP) in immunocompromised patients. Pneumocystis pneumonia is spread through airborne transmission and classically affects patients with AIDS, functioning as an AIDS-defining illness. Patients may present with insidious onset of fever, chills, dry cough, chest pain, and shortness of breath. Pneumocystis jiroveci/Pneumocystis Pneumonia (PCP))
  • Malignancy (e.g., bronchoalveolar cell carcinoma):
    • Note that ILDs such as COP may occur secondary to dermatomyositis and malignancy; however, lung malignancies such as bronchoalveolar cell carcinoma can mimic the symptoms and signs of ILD.

References

  1. Kasper DL, Fauci AS, Hauser SL, Longo DL, Lameson JL, Loscalzo J. Harrison’s Principles of Internal Medicine. New York, NY: McGraw-Hill Education; 2018.
  2. King TE, Raj R. Role of lung biopsy in the diagnosis of interstitial lung disease, in UpToDate Evidence-Based Medicine. Retrieved on August 18, 2020, from https://www.uptodate.com/contents/role-of-lung-biopsy-in-the-diagnosis-of-interstitial-lung-disease?search=interstitial-lung-disease&topicRef=4310&source=see_link#H4256910517

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