Hypersensitivity pneumonitis

Last reviewed: 27 Oct 2022
Last updated: 01 Nov 2022

Summary

Definition

History and exam

Key diagnostic factors

  • exposure to avian protein antigen, especially excrement
  • mould in work environment
  • occupational exposure to chemicals
  • dyspnoea
  • cough
More key diagnostic factors

Other diagnostic factors

  • fever/chills
  • malaise
  • weight loss/anorexia
  • bibasilar rales
  • diffuse rales
  • clubbing
Other diagnostic factors

Risk factors

  • smoking
  • viral infection
  • exposure to avian protein antigen
  • exposure to mould antigen
  • exposure to bacterial antigen
  • exposure to diisocyanate (e.g., epoxy resin)
  • exposure to acid anhydride antigen (e.g., paint refinisher)
  • exposure to metalworking fluid
  • nitrofurantoin, methotrexate, roxithromycin, and rituximab
  • herbal supplements with ayurvedic medicine
More risk factors

Diagnostic investigations

1st investigations to order

  • Chest x-ray
  • CT chest
  • serum IgG
  • pulmonary function test
  • diffusing lung capacity of carbon monoxide
More 1st investigations to order

Investigations to consider

  • bronchoalveolar lavage
  • lung biopsy
More investigations to consider

Treatment algorithm

ACUTE

all patients

Contributors

Authors

Leslie Grammer, MD

Professor

Northwestern University Feinberg School of Medicine

Director

Ernest S. Bazley Asthma and Allergy Center

Clinic Practice Director

Allergy-Immunology

Northwestern Medical Faculty Foundation

Chicago

IL

Disclosures

LG declares that she has no competing interests.

Peer reviewers

Jordan Fink, MD

Professor of Pediatrics

Allergy-Immunology Division

Medical College of Wisconsin

Milwaukee

WI

Disclosures

JF is an author of a number of references cited in this topic.

Alec Chessman, MD

Professor of Family Medicine

Medical University of South Carolina

Charleston

SC

Disclosures

AC declares that he has no competing interests.

Toby M. Maher, MB, MSc, PhD, MRCP

Consultant Respiratory Physician

Interstitial Lung Disease Unit

Royal Brompton Hospital

London

UK

Disclosures

TMM has received consultancy fees from GSK, Actelion, and Philips Respironics. He has received lecture fees from Astra Zeneca and holds an unrestricted industry-academic grant from GSK.

  • Differentials

    • Viral pneumonia
    • Sarcoidosis
    • Bronchiolitis obliterans
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  • Guidelines

    • Diagnosis of hypersensitivity pneumonitis in adults. An official ATS/JRS/ALAT clinical practice guideline
    • Japanese guidelines for occupational allergic diseases 2020
    More Guidelines
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