Practice Based Learning: The young welder’s lung: Hypersensitivity Pneumonitis

Uriel Castañeda

Presented by Uriel Castañeda, MD PGY-1

Clinical Questions

  • When should we think about Hypersensitivity Pneumonitis (HP) in our differential diagnosis?
  • Do you need advanced imaging and invasive diagnostic techniques to diagnose HP?

What is Hypersensitivity Pneumonitis?

  • Rare interstitial lung disease AKA: exogenous allergicalveolitis
    • Immune-mediated inflammatory lung disease affecting the distal portions of the lung
    • Immune-complex mediated Type III and T-Cell complex mediated Type IV immune mechanisms
  • Results from repeated exposure to a wide variety of organic particles, including mammalian and avian proteins, fungi, thermophilic bacteria, and certain small-molecular-weight volatile and nonvolatile chemical compounds
  • Pathology: diffuse and predominantly mononuclear cell inflammation of the small airways and pulmonary parenchyma, often you’ll see poorly formed, nonnecrotizing granulomas
  • Classical Classification (acute <1wk, subacute1-4wks, chronic >1 month)
    • Acute symptoms mimic flu-like illness with high fever, dry cough, dyspnea, and malaise.
  • Can lead to irreversible lung damage, but children usually do well

Take Home Points

  • If appears as atypical pneumonia on CXR but patient with concerning physical exam and clinical presentation then consider HP or other interstitial lung diseases
  • For adolescent patients, don’t forget about the HEADSS assessment
  • Thorough exposure history is critical to detect potential antigens, be nosy!
  • Don’t have to bronch or take biopsy if HPI, exposures, and CXR very convincing.
  • CT can be extremely helpful though
  • The key is to identify antigen and eliminate further exposure!
  • Corticosteroids seem to work well in HP


Buchvald F, Petersen BL, Damgaard K, et al. Frequency, treatment, and functional outcome in children with hypersensitivity pneumonitis. Pediatr Pulmonol. 2011 Nov;46(11):1098-107.

Fan LL. Hypersensitivity pneumonitis in children. Curr Opin Pediatr. 2002 Jun; 14(3): 323-6.

Griese M, Haug M, Hartl D, et al. Hypersensitivity pneumonitis: lessons for diagnosis and treatment of a rare entity in children. Orphanet J Rare Dis. 2013 Aug 8;8:121.

Ratjen F, Costabel U, Griese M, Paul K. Bronchoalveolar lavage fluid findings
in children with hypersensitivity pneumonitis. Eur Respir J. 2003 Jan;21(1):144-8.

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