A 33-year-old farmer presents to the clinic with symptoms of recurrent wheezing and coughing after working in a barn where hay is stored. He has no prior history of asthma, and is not taking any medications. On physical examination, there are bibasilar crackles on auscultation of the lungs, the heart sounds are normal, JVP is 2 cm above the sternal angle, and there is no peripheral edema.His laboratory investigations are normal with no increase in eosinophils on the CBC. The chest x-ray (CXR) reveals patchy lower lobe infiltrates, and a normal cardiac silhouette. Which of the following is the most likely diagnosis?
Hypersensitivity pneumonitis is an inflammatory disorder of the lungs involving alveolar walls and terminal airways that is caused by repeated exposure to organic agents. In this example of "farmer's lung," the inhalation of antigens present in moldy hay such as thermophilic actinomyces ox Aspergillus species are the causative agents. When exposure to moldy hay is stopped, symptoms and signs of farmer's lung all tend to abate and complete recovery usually follows. In acute syndromes, the presentation is 4-8 hours after exposure. Symptoms include fever, chills, malaise, cough, and dyspnea without wheezing. The rate of disease depends on rainfall (which promotes fungal growth) and agricultural practices related to turning and stacking hay. In acute and subacute presentations, removing exposure to the antigen will result in complete recovery. COPD and bronchiectasis are less likely given the absence of prior smoking exposure or lung injury, and both of these disorders usually do have an associated pulmonary infiltrate on CXR unless there is an concomitant lung infection. Asthma can cause wheezing symptoms, and even have mold or dust as triggers but again there is no infiltrate seen on the CXR.
asthma
chronic obstructive lung disease
hypersensitivity pneumonitis
bronchiectasis
Respiratory