Presented by Uriel Castañeda, MD PGY-1
- 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.