What Is It, Causes, Symptoms, and More

Author: Nikol Natalia Armata, MD

Editors: Alyssa Haag, Emily Miao, PharmD, Kelsey LaFayette, DNP

Illustrator: Jessica Reynolds, MS

Copyeditor: David G. Walker

What is alveolitis?

Alveolitis refers to the inflammation of the alveoli, which are the small air sacs  in the lungs where oxygen and carbon dioxide exchange takes place. This inflammation is typically triggered by the inhalation of various allergens or other irritants, thereby leading to an immune response in the lungs. Alveolitis is the earliest manifestation of interstitial lung disease (ILD), a lung disease that primarily affects the interstitium, which is the tissue surrounding the alveoli. Exposure to allergens or irritants leads to the recruitment of macrophages, lymphocytes, and polymorphonuclear neutrophils (PMNs); thereby resulting in chronic inflammation, which leads to chronic or fibrotic lesions. 

Inflamed alveoli.

What causes alveolitis?

Alveolitis can be caused by infections, environmental exposures, and autoimmune disorders. Some cases of alveolitis are also idiopathic where the underlying cause remains unknown. Infections are the most common cause and can include viral pneumonia (e.g., influenza or COVID-19), bacterial pneumonia (e.g. Streptococcus pneumoniae), and fungal infections (e.g., histoplasmosis and aspergillosis).

Environmental factors also play a pivotal role. The inhalation of allergens, pollutants, chemicals, or toxins contributes to alveolitis and may cause hypersensitivity pneumonitis (HP), which is characterized by inflammation of the lung tissue due to an excessive response of the immune system to an extrinsic allergen. Moreover, autoimmune diseases (e.g., rheumatoid arthritis, systemic lupus erythematosus, and sarcoidosis) can also have lung manifestations and may present with inflammation within the alveoli. Connective tissue diseases, like scleroderma and systemic sclerosis, can also affect the lungs and cause alveolitis. Additionally, smoking tobacco poses a significant risk of developing alveolitis as it tends to induce chronic obstructive pulmonary disease (COPD) (e.g., chronic bronchitis or emphysema), which causes lung inflammation and erosion of the alveoli. 

In a subset of cases, alveolitis can be idiopathic with no underlying cause, thereby diagnosed as idiopathic pulmonary fibrosis (IPF). Furthermore, certain medications, such as chemotherapy drugs (e.g., bleomycin, everolimus, erlotinib) and immunosuppressive agents (e.g., azathioprine, cyclophosphamide, methotrexate), have the potential to incite drug-induced alveolitis. Additionally, radiation therapy utilized in the treatment of chest or lung cancer may occasionally cause alveolitis

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What are the signs and symptoms of alveolitis?

The signs and symptoms of alveolitis vary depending on the underlying cause. One of the most common symptoms is shortness of breath, which may have a gradual onset and progressively worsen to the point of disrupting everyday activities. Additionally, individuals with alveolitis often present with a persistent, dry cough. Fatigue is a prevalent issue for those affected by alveolitis, manifesting as an overall sense of weariness. Furthermore, some individuals may experience chest discomfort or pain, particularly during deep inspiration, which is known as pleuritic pain. In certain cases, clubbing of the fingers and toes may develop, characterized by the enlargement of fingertips and curved nails.

Healthcare professionals may detect pathological breath sounds, such as crackles, which sound like Velcro, on auscultation. Fever may accompany alveolitis if it results from an underlying infection. Moreover, specific types of interstitial lung diseases, such as rheumatoid arthritis-associated interstitial pneumonia, can also be related to systemic signs and symptoms like  joint pain and inflammation—often in conjunction with respiratory symptoms. 

How is alveolitis diagnosed?

Diagnosing alveolitis initially requires a thorough clinical examination and review of medical history, focusing on symptom onset, potential risk factors, and exposures, conducted by a healthcare professional. Blood tests may be ordered to uncover the underlying causes of alveolitis, which can include autoimmune antibodies (e.g., rheumatoid factor [RF], antinuclear antibodies [ANA])  or markers indicative of inflammation (e.g., white blood cell count [WBC], c-reactive protein [CRP]). Imaging studies, including chest X-rays and high-resolution computed tomography (HRCT) scans of the chest, are of high importance in revealing lung tissue abnormalities, such as inflammation, scarring, and alveolar changes. CT scanning is particularly sensitive to detecting subtle alterations within the lungs. Pulmonary function tests (PFTs) play a vital role in assessing lung function and determining the severity of lung disease. These tests encompass spirometry as well as diffusion capacity testing, which evaluates how efficiently oxygen moves from the lungs into the bloodstream.

In certain scenarios, a bronchoscopy may be recommended to collect lung tissue samples via biopsy or bronchoalveolar lavage (BAL) fluid for microscopic examination to rule out infections and other lung conditions.

For a definitive diagnosis of alveolitis and determination of its underlying cause, a lung biopsy is required. Multiple techniques exist for procuring lung tissue samples, including  surgical lung biopsy and transbronchial lung biopsy.

How is alveolitis treated?

The treatment of alveolitis is based on the underlying cause. Of note, certain subtypes of ILDs are characterized by a progressive and irreversible course, whereas others may be managed with effective treatment. The primary objectives of treatment strategies nonetheless are to alleviate distressing symptoms; slow the progression of the disease; and, whenever possible, address the root cause. Antibiotics (e.g., azithromycin, levofloxacin) or antifungal medications (e.g., fluconazole) are prescribed to treat infections. Efforts may also be made to minimize or eliminate environmental exposures to irritants (e.g., staying indoors, wearing a mask). Corticosteroids are also frequently prescribed to address lung inflammation. Prednisone, a corticosteroid, is the typical choice for ILDs that exhibit an autoimmune component, such as rheumatoid arthritis-associated ILD. In instances where autoimmune diseases are the underlying cause, immunosuppressive drugs like azathioprine, mycophenolate, or cyclophosphamide may be combined with corticosteroids to modulate the immune response effectively.

For ILDs marked by lung fibrosis, as seen in  idiopathic pulmonary fibrosis (IPF), antifibrotic drugs like pirfenidone and nintedanib are employed to halt disease advancement and alleviate symptoms.

Supplemental oxygen therapy can be administered to enhance oxygen levels in the bloodstream, offering relief to individuals with compromised lung function. Pulmonary rehabilitation programs, comprising tailored exercises and educational components, are pivotal for augmenting lung function and improving overall physical well-being.

In situations where conservative treatments are inadequate in severe ILD cases, lung transplantation may be necessary. Overall, regular follow-up care with a pulmonary specialist for monitoring disease progression and fine-tuning treatment approaches is essential for individuals with persistent alveolitis or ILDs. 

What are the most important facts to know about alveolitis?

Alveolitis is inflammation of the lung's alveoli often triggered by allergens or irritants and is an early sign of interstitial lung disease. Causes include infections; environmental exposures; autoimmune disorders; and sometimes, they are unknown. Symptoms vary but can include shortness of breath, cough, fatigue, and chest discomfort. Diagnosis involves clinical evaluation, blood tests, imaging (e.g., X-rays, CT scans), pulmonary function testing, and (sometimes) bronchoscopy or lung biopsy. Treatment depends on the underlying cause,  and in severe cases, lung transplantation may be considered.

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Related links

Alveolar gas equation
Alveolar surface tension and surfactant
Bronchioles and alveoli histology

Resources for research and reference

Haschek WM, Rousseaux CG, Wallig MA. Respiratory System. Fundamentals of Toxicologic Pathology. 2010:93-133. doi:10.1016/b978-0-12-370469-6.00006-4 

Hypersensitivity Pneumonitis. Published May 5, 2023. Accessed October 1, 2023. 

Hypersensitivity Pneumonitis. NIH. Published March 24, 2022.

Keogh BA, Crystal RG. Alveolitis: The key to the interstitial lung disorders. Thorax. 1982;37(1):1-10. doi:10.1136/thx.37.1.1 

Raghu G, Remy-Jardin M, Ryerson CJ, et al. Diagnosis of hypersensitivity pneumonitis in adults: An official ATS/JRS/ALAT clinical practice guideline. Am J Respir Crit Care Med. 2020;202(3):e36-e69. doi:10.1164/rccm.202005-2032ST

Watts MM, Grammer LC. Hypersensitivity pneumonitis. Allergy Asthma Proc. 2019;40(6):425-428. doi:10.2500/aap.2019.40.4263