Hypersensitivity Pneumonitis Diagnosis and Management

Clinical Presentation and Diagnosis

The American College of Chest Physicians suggests that chronic cough for 3 months is a common presenting symptom of Hypersensitivity Pneumonitis (HP), along with dyspnea 1
Elevated specific IgG antibodies to fungal antigens, such as Cladosporium and Phoma species, support the diagnosis of HP, as demonstration of specific serum IgG antibodies to the suspected agent further supports HP diagnosis 1
Reduced DLCO (70%) is characteristic of HP, as pulmonary function tests show reduced diffusing capacity especially on exercise 1
Hyperinflation pattern can occur in chronic HP with bronchiolitis, where chronic airflow limitation may predominate 1
The American College of Radiology recommends chest CT for chronic cough when interstitial lung disease is suspected, especially with reduced DLCO 2, 3

High-Resolution CT (HRCT) chest is essential for distinguishing chronic HP from other interstitial lung diseases and should be performed before proceeding with invasive testing, according to the American College of Radiology 1, 2
Ground-glass appearance on HRCT is helpful in distinguishing chronic HP from idiopathic pulmonary fibrosis 1
CT is indicated when clinical suspicion of underlying pulmonary disease exists, particularly with abnormal PFTs and positive fungal antibodies 2

Indoor fungal contamination, including contaminated humidifiers, vaporizers, hot tubs, and swimming pool areas, should be assessed 1
Home environment should be evaluated for water damage, visible mold, or areas generating fungal bioaerosol exposures 1
Occupational exposures to organic dusts or contaminated environments should be considered 1
Temporal relationship between symptoms and specific environments should be evaluated, as suspicion increases if respiratory findings are intermittent in relation to exposures and clear up after a few days away 1

Early identification and removal from further exposure are key components of treatment for HP, making environmental assessment and HRCT imaging urgent priorities 1
Bronchoalveolar lavage (BAL) may be considered if HRCT shows findings consistent with HP, as BAL findings of predominant lymphocytosis support HP diagnosis 1
Lung biopsy may be needed if diagnosis remains uncertain, as findings of giant cell granulomas raise suspicion of HP 1