Sections View Full Chapter Figures Tables Videos Annotate Full Chapter Figures Tables Videos Supplementary Content + Download Section PDF Listen ++ For further information, see CMDT Part 9-32: Occupational Pulmonary Diseases + Key Features Download Section PDF Listen +++ +++ Essentials of Diagnosis ++ A link between symptoms and antigen exposure may be obtained from work or environmental history Antigen can be microbial agents, animal proteins, or chemical sensitizers Presentation can be acute or subacute illness +++ General Considerations ++ A nonatopic, nonasthmatic inflammatory pulmonary disease (also called extrinsic allergic alveolitis) Manifested mainly as occupational disease where exposure to an inhaled organic antigen leads to an acute illness Causes See Table 9–23 Farmer's lung (moldy hay) "Humidifier" lung (contaminated humidifier, heating, or air conditioning) Bird fancier's lung ("pigeon breeder's disease") Bagassosis (moldy sugar cane fiber) Sequoiosis (moldy redwood sawdust) Maple bark stripper's disease Mushroom picker's disease (moldy compost) Suberosis (moldy cork dust) Detergent worker's lung (enzyme additives) ++Table Graphic Jump LocationTable 9–23.Selected causes of hypersensitivity pneumonitis.View Table||Download (.pdf) Table 9–23. Selected causes of hypersensitivity pneumonitis. Disease Antigen Source Farmer’s lung Micropolyspora faeni, Thermoactinomyces vulgaris Moldy hay “Humidifier” lung Thermophilic actinomycetes Contaminated humidifiers, heating systems, or air conditioners Bird fancier’s lung Avian proteins Bird serum and excreta Bagassosis Thermoactinomyces sacchari and T vulgaris Moldy sugar cane fiber (bagasse) Sequoiosis Graphium, Aureobasidium, and other fungi Moldy redwood sawdust Maple bark stripper’s disease Cryptostroma (Coniosporium) corticale Rotting maple tree logs or bark Mushroom picker’s disease Same as farmer’s lung Moldy compost Suberosis Penicillium frequentans Moldy cork dust Detergent worker’s lung Bacillus subtilis enzyme Enzyme additives + Clinical Findings Download Section PDF Listen +++ +++ Symptoms and Signs ++ Acute illness 4–8 hours after exposure characterized by Malaise Chills Fever Cough Dyspnea Nausea Bibasilar crackles, tachypnea, tachycardia, and (occasionally) cyanosis are found Subacute and chronic illness (15% of cases) Insidious onset of chronic cough and progressive dyspnea Anorexia Weight loss +++ Differential Diagnosis ++ Sarcoidosis Asthma Atypical pneumonia Collagen vascular disease, eg, systemic lupus erythematosus Idiopathic pulmonary fibrosis Lymphoma + Diagnosis Download Section PDF Listen +++ +++ Laboratory Tests ++ Pulmonary function studies show a restrictive pattern with decreased diffusion capacity WBC shows leukocytosis with a left shift Arterial blood gases show hypoxemia Hypersensitivity pneumonitis antibody panels are available; positive results while supportive do not establish a definitive diagnosis +++ Imaging Studies ++ Chest radiograph classically shows small nodular densities sparing the apices and bases Pulmonary fibrosis may be found with repeated exposure to the offending agent +++ Diagnostic Procedures ++ Bronchoscopy with bronchoalveolar lavage Surgical lung biopsy may be necessary + Treatment Download Section PDF Listen +++ +++ Medications ++ Corticosteroids (prednisone, 0.5 mg/kg/day as single morning dose for 2 weeks, tapered to nil over 4–6 weeks) +++ Therapeutic Procedures ++ Identification of the offending agent with removal or avoidance Change in occupation is often unavoidable + Outcome Download Section PDF Listen +++ +++ Follow-Up ++ Monitor serial chest radiographs and pulmonary function tests +++ Complications ++ Progressive pulmonary fibrosis and respiratory failure due to chronic exposure +++ Prognosis ++ Good if diagnosed early and offending agent is avoided +++ When to Refer ++ For assistance in diagnosis, treatment, and follow-up +++ When to Admit ++ Hypoxemic respiratory failure + References Download Section PDF Listen +++ + +Elicker BM et al. Multidisciplinary approach to hypersensitivity pneumonitis. J Thorac Imaging. 2016 Mar;31(2):92–103. [PubMed: 26479131] + +Nogueira R et al. Hypersensitivity pneumonitis: antigen diversity and disease implications. Pulmonology. 2019 Mar–Apr;25(2):97–108. [PubMed: 30126802] + +Raj R et al. Surgical lung biopsy for interstitial lung diseases. Chest. 2017 May;151(5):1131–40. [PubMed: 27471113] + +Soumagne T et al. Current and emerging techniques for the diagnosis of hypersensitivity pneumonitis. Expert Rev Respir Med. 2018 Jun;12(6):493–507. [PubMed: 29727203]