The industrial hygeinst or environmental scientist will make the decision to conduct additional sampling. Types
Hypersensitivity pneumonitis may also be called many different names, based on the provoking antigen. These include:

Of these types, Farmers Lung and Bird-Breeders Lung are the most common. "Studies document 8-540 cases per 100,000 persons per year for farmers and 6000-21,000 cases per 100,000 persons per year for pigeon breeders. High attack rates are documented in sporadic outbreaks. Prevalence varies by region, climate, and farming practices. HP affects 0.4–7% of the farming population. Reported prevalence among bird fanciers is estimated to be 20-20,000 cases per 100,000 persons at risk." Imaging
No single imaging finding is singularly definitive of a diagnosis rather clinicians rely on a constellation of findings. Both chest radiographs and high resolution CT scans can be normal. Chest Radiographs
Acute presentation may reveal poorly defined a micro-nodular interstitial pattern and ground-glass opacities in the lower and mid lung zones. In addition to this, subacute presentations may show reticular nodular opacities in mid-to-lower lung zones. Chronic forms may show fibrotic changes and appear like Idiopathic pulmonary fibrosis. High-Resolution Computed Tomography
This has become a common diagnostic imaging for the diagnosis and is the modality used in the Official ATS/JRS/ALAT Clinical Practice Guideline. Two forms of hypersensitivity pneumonitis are fibrotic and non-fibrotic findings on chest CT. The two differ in terms of their diagnostic work up and management although there is overall between them. The non-fibrotic form is typically characterized by ground glass opacities, mosaic attenuation, ill-defined centrilobular nodules (<5 mm), and air trapping.
If avoidance is not possible, such as in the case of some workplace exposures, minimizing exposure can be accomplished through various means including the implementation of PPE or proper ventilation of a workplace. Corticosteroids such as prednisolone may help to control symptoms but may produce side-effects. In the case of severe, end-stage pulmonary fibrosis arising from chronic exposure, lung transplant may be the only viable option. In addition to steroids for fibrotic disease, other immunosuppressants (Azathioprine, Mycophenolic acid) and anti-fibrotic agents (Nintedanib) may be used although their effectiveness is unclear

Prognosis
There are few studies examining longitudinal outcomes in patients diagnosed with hypersensitivity pneumonitis. One study in the US showed about a 0.09 to 0.29 per million increase in mortality rates although the cause specific cause was unclear. Most of the outcomes collected are from patients diagnosed with farmers or bird breeders lung and thus the degree to which this data can be extrapolated to other types of HP is uncertain. Generally outcomes for HP in those with acute disease are very good if exposure is avoided. However, those with subacute or chronic type, especially with biopsy proven fibrosis fair much poorer death rates comparable to people diagnosed with Interstitial pulmonary fibrosis. Additional images
See also
Dust pneumonia
Pneumonitis

References


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