Sections

Presentation

History

The clinical presentation of hypersensitivity pneumonitis (HP) is categorized as acute, subacute, or chronic, according to duration of illness.

Acute hypersensitivity pneumonitis clinical presentation is as follows:

Flulike syndrome including fever, chills, malaise, cough, chest tightness, dyspnea, and headache
Develops within hours following significant exposure
Symptoms typically resolve gradually within 12 hours to several days following exposure removal
May recur following re-exposure

Subacute (intermittent) hypersensitivity pneumonitis clinical presentation is as follows:

Insidious onset of productive cough, dyspnea, fatigue over weeks to months
Progression to persistent cough and dyspnea
May occur in individuals with frequent acute reactions
May note anorexia and/or weight loss

Chronic hypersensitivity pneumonitis clinical presentation is as follows:

May have unrecognized or untreated acute/subacute disease
Often presents with no obvious acute episodes, presents as insidious disease
Progressive dyspnea, cough, fatigue, malaise, and/or weight loss

Physical Examination

Physical examination findings of hypersensitivity pneumonitis (HP) vary according to clinical presentation.

Patients with acute hypersensitivity pneumonitis present with fever, tachypnea, and diffuse fine bibasilar crackles upon auscultation.

Patients with subacute hypersensitivity pneumonitis present similarly to patients with acute disease, but symptoms are generally less severe and have lasted longer.

Patients with chronic hypersensitivity pneumonitis present with muscle wasting and weight loss. Clubbing is observed in 50% of patients. Tachypnea, respiratory distress, and inspiratory crackles over lower lung fields often are present.

Acute on chronic hypersensitivity pneumonitis is generally severe and often presents with respiratory distress requiring ventilation assistance.

Differential Diagnoses

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Media Gallery

A 60-year-old dairy farmer had an 8-year history of intermittent dyspnea. Chest radiograph shows bilateral reticulonodular interstitial infiltration secondary to subacute hypersensitivity pneumonitis.
Chest radiograph of a patient with chronic hypersensitivity pneumonitis from pigeon breeder's disease. Bilateral reticulonodular densities are present.
High-resolution CT scan of lungs shows ground-glass opacification in the acute phase of hypersensitivity pneumonitis.
The chronic phase of hypersensitivity pneumonitis shows honeycombing in the right upper lung and traction bronchiectasis.
High-resolution chest CT scan of a patient with subacute hypersensitivity pneumonitis demonstrates centrilobular nodules. These nodules are unlike those of sarcoidosis, in which the nodules are subpleural and along bronchovascular bundles.
Light microscopy shows mononuclear infiltration and noncaseating granulomas usually observed in association with acute hypersensitivity pneumonitis, but it also can be observed in subacute and chronic disease.
Giant cells are a characteristic feature of hypersensitivity pneumonitis.
Chronic hypersensitivity pneumonitis shows interstitial inflammation associated with fibrosis.

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Author

Caleb Hsieh, MD, MS Clinical Instructor in Pulmonary, Critical Care, and Sleep Medicine, University of California, Los Angeles, David Geffen School of Medicine

Caleb Hsieh, MD, MS is a member of the following medical societies: American College of Physicians, American Medical Association

Disclosure: Nothing to disclose.

Coauthor(s)

Nader Kamangar, MD, FACP, FCCP, FCCM Professor of Clinical Medicine, University of California, Los Angeles, David Geffen School of Medicine; Chief, Division of Pulmonary and Critical Care Medicine, Vice-Chair, Department of Medicine, Olive View-UCLA Medical Center

Nader Kamangar, MD, FACP, FCCP, FCCM is a member of the following medical societies: Academy of Persian Physicians, American Academy of Sleep Medicine, American Association for Bronchology and Interventional Pulmonology, American College of Chest Physicians, American College of Critical Care Medicine, American College of Physicians, American Lung Association, American Medical Association, American Thoracic Society, Association of Pulmonary and Critical Care Medicine Program Directors, Association of Specialty Professors, California Sleep Society, California Thoracic Society, Clerkship Directors in Internal Medicine, Society of Critical Care Medicine, Trudeau Society of Los Angeles, World Association for Bronchology and Interventional Pulmonology

Disclosure: Nothing to disclose.

Specialty Editor Board

Francisco Talavera, PharmD, PhD Adjunct Assistant Professor, University of Nebraska Medical Center College of Pharmacy; Editor-in-Chief, Medscape Drug Reference

Disclosure: Received salary from Medscape for employment. for: Medscape.

Daniel R Ouellette, MD, FCCP Associate Professor of Medicine, Wayne State University School of Medicine; Medical Director, Pulmonary Medicine General Practice Unit (F2), Senior Staff and Attending Physician, Division of Pulmonary and Critical Care Medicine, Henry Ford Hospital

Daniel R Ouellette, MD, FCCP is a member of the following medical societies: American College of Chest Physicians, American Thoracic Society, Society of Critical Care Medicine

Disclosure: Received research grant from: Sanofi Pharmaceutical.

Chief Editor

John J Oppenheimer, MD Clinical Professor, Department of Medicine, Rutgers New Jersey Medical School; Director of Clinical Research, Pulmonary and Allergy Associates, PA

John J Oppenheimer, MD is a member of the following medical societies: American Academy of Allergy Asthma and Immunology, American College of Allergy, Asthma and Immunology, New Jersey Allergy, Asthma and Immunology Society

Disclosure: Serve(d) as a director, officer, partner, employee, advisor, consultant or trustee for: Amgen; GSK; Aquestive; Aimmune<br/>Clinical Adjudication/Data Safety Monitoring Board for AZ, GSK, Abbvie, Sanofi; Executive Editor for Annals of Allergy, Asthma & Immunology; Editor for Medscape; Reviewer for UpToDate; Honoraria from American Board of Allergy and Immunology.

Additional Contributors

Michael Peterson, MD Chief of Medicine, Vice-Chair of Medicine, University of California, San Francisco, School of Medicine; Endowed Professor of Medicine, University of California, San Francisco-Fresno, School of Medicine

Michael Peterson, MD is a member of the following medical societies: American College of Chest Physicians, American College of Physicians, American Thoracic Society

Disclosure: Nothing to disclose.

Acknowledgements

Marine Demirjian, MD Resident Physician, Department of Internal Medicine, Ronald Reagan University of California in Los Angeles Medical Center

Marine Demirjian, MD is a member of the following medical societies: American College of Physicians, American Medical Association, American Medical Women's Association, and California Medical Association

Disclosure: Nothing to disclose.

Sat Sharma, MD, FRCPC Professor and Head, Division of Pulmonary Medicine, Department of Internal Medicine, University of Manitoba; Site Director, Respiratory Medicine, St Boniface General Hospital

Sat Sharma, MD, FRCPC is a member of the following medical societies: American Academy of Sleep Medicine, American College of Chest Physicians, American College of Physicians-American Society of Internal Medicine, American Thoracic Society, Canadian Medical Association, Royal College of Physicians and Surgeons of Canada, Royal Society of Medicine, Society of Critical Care Medicine, and World Medical Association

Disclosure: Nothing to disclose.

Disease	Source of Exposure	Major Antigen
Farmer's lung	Moldy hay	Saccharopolyspora rectivirgula (Micropolyspora faeni)
Bagassosis	Moldy sugar cane fiber	Thermoactinomyces sacchari
Grain handler's lung	Moldy grain	S rectivirgula,Thermoactinomyces vulgaris
Humidifier/air-conditioner lung	Contaminated forced-air systems, heated water reservoirs^[13]	S rectivirgula, T vulgaris, Candida guilliermondii
Bird breeder's lung	Pigeons, parakeets, fowl, rodents	Avian or animal proteins^[14]
Cheese worker's lung	Cheese mold	Penicillium casei
Malt worker's lung	Moldy malt	Aspergillus clavatus
Paprika splitter's lung	Paprika dust	Mucor stolonifer
Wheat weevil	Infested wheat	Sitophilus granarius
Mollusk shell hypersensitivity	Shell dust	Sea snail shells
Chemical worker's lung	Manufacture of plastics, polyurethane foam, rubber	Trimellitic anhydride, diisocyanate, methylene diisocyanate

Hypersensitivity Pneumonitis Clinical Presentation

History

Physical Examination

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