Diagnostic Considerations

Other conditions to consider in the differential diagnosis include the following:

Acute hypersensitivity pneumonitis (HP) closely resembles viral or bacterial infections of the lower respiratory tract.
Bird exposure can place the patient at risk for psittacosis.
Granulomatous lung diseases (eg, tuberculosis, histoplasmosis, coccidiomycosis, sarcoidosis) can also produce findings similar to those of subacute hypersensitivity pneumonitis.^[11]
Lymphoid interstitial pneumonitis observed in patients with acquired immunodeficiency syndrome (AIDS) can manifest as dyspnea, crackles, interstitial infiltrates, and hypergammaglobulinemia.
For patients residing or working in a farm setting, organic toxic dust syndrome can be provoked by bacterial endotoxins or fungal toxins.^[73]
Zamboni disease (a toxic reaction to nitrogen oxides emitted from an ice-smoothing machine operated in an indoor ice rink) can mimic acute or subacute hypersensitivity pneumonitis.^[74]
Differentiating chronic hypersensitivity pneumonitis from idiopathic pulmonary fibrosis is particularly important because the prognosis for the former improves when the offending antigen is identified and eliminated.
Subacute and chronic hypersensitivity pneumonitis has been misdiagnosed as asthma, a condition that can also cause cough, dyspnea, and exercise intolerance.^[2]
Chronic hypersensitivity pneumonitis may be misdiagnosed as anorexia nervosa. Anorexia, weight loss, and exercise intolerance are manifestations of both diseases.
Connective-tissue disease (eg, systemic lupus erythematosus) can cause noninfectious pneumonitis with fever and weight loss, but other clinical and laboratory features of the connective tissue disease are expected.
Drug-induced pneumonitis is considered separately from pneumonitis triggered by inhaled antigens. Medications most often implicated in drug-induced pneumonitis include gold salts, methotrexate, and amiodarone. Rare causes of drug-induced pneumonitis are the nonsteroidal anti-inflammatory drugs aspirin and ibuprofen; the anticonvulsants carbamazepine and phenytoin; the antibiotics nitrofurantoin and dapsone; the sulfonamides sulfasalazine and sulfadoxine; the antimalarial chloroquine; the immunosuppressants penicillamine and cyclophosphamide; and the cytotoxic agents azathioprine, bleomycin, chlorambucil, cyclophosphamide, mitomycin, and vinblastine.

Differential Diagnoses

Workup

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Media Gallery

Photomicrograph of a lung biopsy specimen reveals marked interstitial inflammation with lymphocytic predominance and a multinucleated giant cell (hematoxylin-eosin stain, original magnification 40X). Reprinted with permission from Farber and Budson, 2000.
Photomicrograph of a lung biopsy sample reveals interstitial fibrosis with active interstitial inflammation (hematoxylin-eosin stain, original magnification 10X). Reprinted with permission from Farber and Budson, 2000.
Photograph reveals precipitin lines produced by means of Ouchterlony immunodiffusion assay. Central wells contain the patient's serum. Peripheral wells contain serum or droppings from various birds. Reprinted with permission from Farber and Budson, 2000.
14-year-old girl with subacute hypersensitivity pneumonitis from avian antigen exposure. Chest radiograph demonstrates numerous tiny pulmonary nodules bilaterally.
Chest CT from same patient as previous image reveals widespread poorly-defined centrilobular ground-glass nodules related to bronchiolocentric cellular interstitial pneumonia with poorly-formed granulomas.
A 10-year-old girl with chronic hypersensitivity pneumonitis from avian antigen exposure. Chest CT image shows reticular pulmonary opacities and architectural distortion at the lung bases indicative of pulmonary fibrosis.

of 6

Author

Naga Jaya Smitha Yenduri, MD Assistant Professor, Division of Pediatrics, Pulmonary Section, Texas Children's Hospital, Baylor College of Medicine

Naga Jaya Smitha Yenduri, MD is a member of the following medical societies: American Thoracic Society

Disclosure: Nothing to disclose.

Coauthor(s)

R Paul Guillerman, MD Professor, Department of Radiology, University of Cincinnati College of Medicine, Cincinnati Children's Hospital Medical Center

R Paul Guillerman, MD is a member of the following medical societies: American Roentgen Ray Society, Children's Oncology Group, Radiological Society of North America, Society for Pediatric Radiology

Disclosure: Nothing to disclose.

Harold J Farber, MD, MSPH Professor of Pediatrics, Section of Pediatric Pulmonology, Baylor College of Medicine, Texas Children's Hospital; Associate Medical Director, Texas Children's Health Plan

Harold J Farber, MD, MSPH is a member of the following medical societies: American Academy of Pediatrics, American College of Chest Physicians, American Thoracic Society

Disclosure: Serve(d) as a director, officer, partner, employee, advisor, consultant or trustee for: Texas Children's Health Plan (a not-for-profit Medicaid Manged Care program owned by Texas Children's Hospital).

Specialty Editor Board

Mary L Windle, PharmD Adjunct Associate Professor, University of Nebraska Medical Center College of Pharmacy; Editor-in-Chief, Medscape Drug Reference

Disclosure: Nothing to disclose.

Charles Callahan, DO Professor, Chief, Department of Pediatrics and Pediatric Pulmonology, Tripler Army Medical Center

Charles Callahan, DO is a member of the following medical societies: American Academy of Pediatrics, American College of Chest Physicians, American College of Osteopathic Pediatricians, American Thoracic Society, The Society of Federal Health Professionals (AMSUS), Christian Medical and Dental Associations

Disclosure: Nothing to disclose.

Chief Editor

Girish D Sharma, MD, FCCP, FAAP Professor of Pediatrics, Rush Medical College; Director, Section of Pediatric Pulmonology and Rush Cystic Fibrosis Center, Rush Children's Hospital, Rush University Medical Center

Girish D Sharma, MD, FCCP, FAAP is a member of the following medical societies: American Academy of Pediatrics, American College of Chest Physicians, American Thoracic Society, Royal College of Physicians of Ireland

Disclosure: Nothing to disclose.

Acknowledgements

The authors and editors of Medscape Reference gratefully acknowledge the contributions of previous authors Bettina Hilman, MD, Nidhy Paulose Varghese, MD, Lori R Johnson, MD, and Laurianne Wild, MD. Leland Fan, MD, reviewed previous versions and provided helpful suggestions.

Sections Pediatric Hypersensitivity Pneumonitis
Overview
Presentation
DDx
Workup
Treatment
Guidelines
Medication
Follow-up
Media Gallery
Tables
References

Exposure	Disease	Source of Antigen
Avian	Bird fancier's lung, pigeon breeder's lung, poultry worker's lung, feather duvet lung	Feathers, droppings, serum proteins, intestinal mucins, avian immunoglobulin A
Agriculture	Farmer's lung, Bagasse (sugar cane) lung, mushroom worker's lung, potato riddler's lung, paprika slicer's lung, wine maker's lung	Thermophilic actinomycetes, Aspergillus species, and other fungi in moldy hay or grains; moldy sugar cane; mushroom spores and thermophilic actinomycetes; moldy hay around potatoes, thermophilic actinomycetes, and others; Mucor stolonifer (on moldy paprika pods); B cinerea (noble rot on grapes)
Water-based systems	Humidifier lung, hot-tub lung, sauna taker's lung, lifeguard's lung, sewage pneumonitis, wind instrument lung	Aerosolized molds, endotoxins, mycobacteria, thermophilic actinomycetes, Penicillium species, others
Home environment	Summer-type pneumonitis, mold-contaminated walls, humidifiers, wallpaper	Trichosporon species, mold contamination in older and/or water-damaged homes
Chemicals	Chemical worker's lung, epoxy-resin lung, pyrethrum pneumonitis	Exposure to chemicals in manufacturing, laboratories, spray paints, heated epoxy resins, insecticides

Pediatric Hypersensitivity Pneumonitis Differential Diagnoses

Diagnostic Considerations

Differential Diagnoses

References

Tables

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