Inclusion Criteria:

• Diagnosis of Chronic Hypersensitivity Pneumonitis (CHP) defined from the first instance in which a patient was informed of having CHP for at least 3 to 6 months.
• Age 18 through 80 years.
• Diagnosis of CHP by HRCT confirmed by NJH review:
  • Definite CHP: Evidence of lung fibrosis (reticular abnormality and/or, traction bronchiectasis and/or, architectural distortion, and/or honeycombing) and one or more of the associated finding:
    • Multilobular inspiratory mosaic attenuation;
    • Multilobular air trapping on expiratory images;
    • Profuse centrilobular ground glass nodular opacities.
  • Possible CHP: Evidence of lung fibrosis (as above) in the absence of any of above-associated findings:
    • These patients are required to have a known exposure and BAL lymphocytosis (>20%) and/or transbronchial biopsies demonstrating non-necrotizing granulomas and lymphocytosis and/or wedge biopsy with a pattern consistent with HP.
• Able to understand and sign a written informed consent form.
• Able to understand the importance of adherence to the study protocol and willing to follow all study requirements (e.g., completing procedures such as 6-min walk and questionnaires).

Exclusion Criteria:

• Not a suitable candidate for enrollment or unlikely to comply with the requirements of this study (e.g., unstable or deteriorating cardiac disease such as congestive heart failure requiring hospitalization or unstable angina).
• Known explanation for the interstitial lung disease, including but not limited to radiation, drug toxicity, sarcoidosis, pneumoconiosis.
• Clinical diagnosis of any connective tissue disease, including but not limited to scleroderma, polymyositis/dermatomyositis, and rheumatoid arthritis.
• Expected to receive a lung transplant within 4 months from enrollment.
• Pregnant women.