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Hypersensitivity Pneumonitis: Advanced Management

Immune-mediated interstitial lung disease caused by inhalation of organic antigens (bird proteins, mold, bacteria) in sensitized individuals, classified as fibrotic or non-fibrotic by HRCT and biopsy with implications for prognosis, requiring antigen avoidance, corticosteroids, and antifibrotic therapy for fibrotic disease.

Written by: Saygı Hospital Health Guide Editorial Board
Last updated:

This content has been compiled by the Saygı Hospital Health Guide Editorial Board and is periodically reviewed by a specialist physician.

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This content is for informational purposes only and does not constitute medical advice. You can book an appointment at our Göğüs Hastalıkları department. Book Appointment →

What is Hypersensitivity Pneumonitis: Advanced Management?

Hypersensitivity pneumonitis (HP), formerly extrinsic allergic alveolitis, is an immunologically mediated interstitial lung disease (ILD) caused by inhalation of organic antigens (bird proteins in pigeon/parrot fanciers; thermophilic actinomycetes in farmers; mold; chemicals) in sensitized individuals. Common subtypes include farmer's lung, bird fancier's lung, hot tub lung, and mushroom worker's lung.

The 2020 ATS/JRS/ALAT guideline replaced acute/subacute/chronic classification with two categories based on HRCT and histopathology: non-fibrotic HP (predominantly inflammatory ground-glass opacities, mosaic attenuation, centrilobular nodules; better prognosis with antigen avoidance) and fibrotic HP (reticulation, traction bronchiectasis, honeycombing in addition to inflammatory features; poorer prognosis, may progress like IPF).

Diagnosis requires combination of antigen exposure history, HRCT pattern (typical features include centrilobular nodules, mosaic attenuation with three-density sign, fibrosis distribution), bronchoalveolar lavage lymphocytosis (>30%), serum precipitins (low sensitivity/specificity), and lung biopsy (transbronchial, cryobiopsy, or surgical) showing characteristic features (poorly formed granulomas, peribronchiolar fibrosis, lymphocytic infiltrate). Multidisciplinary discussion is essential. Treatment: thorough antigen identification and avoidance (mainstay), corticosteroids (especially non-fibrotic), immunosuppressants (mycophenolate mofetil, azathioprine) for chronic disease, antifibrotic therapy (nintedanib approved for progressive fibrosing ILD including HP) for fibrotic progressive HP, lung transplantation for end-stage.

Symptoms

Cough, dyspnea on exertion (often subacute over weeks-months)
Fever, chills, malaise after antigen exposure (acute episodes)
Weight loss, fatigue (chronic disease)
Inspiratory crackles, occasional inspiratory squeaks
Hypoxemia, cyanosis in advanced disease
Improvement with antigen avoidance (early disease)

Risk Factors

Bird antigen exposure (pigeon, parakeet keeping)
Farming occupations (moldy hay, silage)
Hot tub use (Mycobacterium avium complex)
Mold/dampness in home or workplace
Chemical exposures (isocyanates, anhydrides)
Genetic susceptibility (HLA associations)

When to See a Doctor?

If you experience any of the following symptoms, seek medical attention promptly:

  • Persistent cough and dyspnea with relevant exposure
  • Recurrent flu-like symptoms after antigen contact
  • Progressive dyspnea on exertion with bird/mold exposure
  • Established interstitial lung disease for evaluation of cause
  • Worsening of suspected HP despite antigen avoidance
  • Hot tub or sauna-related respiratory symptoms

Treatment Methods

01
Thorough exposure history (occupational, recreational, residential including pets, hot tubs, mold)
02
HRCT chest with inspiratory and expiratory views (centrilobular nodules, mosaic attenuation, three-density sign, fibrosis pattern)
03
Bronchoscopy with BAL (lymphocytosis >30% supports HP) and transbronchial biopsy or cryobiopsy
04
Serum precipitins (specific IgG to suspected antigens) — low sensitivity
05
Surgical lung biopsy if multidisciplinary diagnosis uncertain
06
Multidisciplinary discussion (pulmonologist, radiologist, pathologist) for diagnosis
07
Mainstay: thorough antigen identification and complete avoidance
08
Non-fibrotic HP: prednisone 0.5-1 mg/kg/day for 4-8 weeks, taper
09
Chronic/relapsing HP: steroid-sparing immunosuppressants (mycophenolate mofetil, azathioprine)
10
Progressive fibrotic HP: antifibrotic therapy (nintedanib approved per INBUILD trial)
11
Lung transplantation for end-stage fibrotic HP
12
Pulmonary rehabilitation, oxygen therapy, vaccinations, infection prevention

Which Department to Visit?

You can visit our Göğüs Hastalıkları department for these complaints. Our specialist physicians will create the most suitable treatment plan for you.

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Health Disclaimer: The information on this page is prepared for general informational purposes only. It does not replace medical diagnosis and treatment. Please consult your physician for your complaints. Saygı Hospital does not accept responsibility for actions taken based on the information on this page.