A 36-year-old woman comes to the clinic for evaluation of a 4-month history of nonproductive cough and exertional dyspnea. Her only other medical problem is frequent heartburn, for which she takes over-the-counter antacids. Temperature is 37.1 C (98.8 F), blood pressure is 126/74 mm Hg, pulse is 88/min, and respirations are 20/min. Examination shows bilateral crackles and normal heart sounds. The remainder of the examination is unremarkable. Chest imaging shows bilateral interstitial opacities. Bronchioalveolar lavage reveals >50% of cells being lymphocytes. Which of the following is the most likely diagnosis?
Hypersensitivity pneumonitis | |
Etiology |
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Clinical presentation | Acute
Chronic
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Diagnosis |
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Treatment |
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BAL = bronchoalveolar lavage; PFT = pulmonary function testing. | |
This patient with several months of nonproductive cough and exertional dyspnea as well as a lymphocyte-predominant bronchoalveolar lavage (BAL) most likely has hypersensitivity pneumonitis (HP). HP results from an exaggerated immunologic response that some individuals develop to an inhaled antigen (eg, mold, animal protein). Those most commonly affected include farmers (ie, farmer's lung due to exposure to moldy hay) and bird keepers (ie, bird fancier's lung due to exposure to avian proteins).
The presentation of HP can be acute or chronic. Acute disease usually involves recurrent episodes of abrupt-onset cough, dyspnea, fever, chills, and fatigue that correlate with intermittent antigen exposure. Chronic disease likely results from chronic, long-term antigen exposure, and presents with gradually progressive cough, dyspnea, fatigue, and weight loss over a period of several months. Lung crackles are present with both acute and chronic disease. Chest x-ray in acute disease is frequently normal, whereas diffuse reticular interstitial opacities are present with chronic disease as a network of interstitial inflammation and fibrosis develops.
Normally, the leukocytes in alveolar fluid consist of approximately 85% alveolar macrophages, 10% lymphocytes, and a small percentage of neutrophils and eosinophils. With both acute and chronic HP, BAL usually shows high relative lymphocyte count (eg, >20%, often >50%), which helps support the diagnosis. Other causes of high relative lymphocyte count in BAL include sarcoidosis, lymphoma, and chronic fungal or mycobacterial infection.
(Choice A) Asbestosis can present with progressive dyspnea and cough, but BAL typically shows increased neutrophils and characteristic asbestos bodies.
(Choice B) Asthma is expected to cause wheezing rather than crackles on lung auscultation. BAL may show increased eosinophils as well as bronchial epithelial cells.
(Choice C) Patients with gastroesophageal reflux disease can have chronic microaspiration, leading to respiratory symptoms (eg, cough, dyspnea). However, BAL typically shows increased neutrophils and characteristic lipid-laden macrophages that result from the aspiration of lipid-containing food or drink.
(Choice E) BAL in cardiogenic pulmonary edema often demonstrates hemosiderin-laden macrophages, resulting from elevated pulmonary capillary hydrostatic pressure leading to extravasation of red blood cells into the alveoli. Leukocyte percentages are not significantly affected.
Educational objective:
Hypersensitivity pneumonitis results from an exaggerated immunologic response to an inhaled antigen (eg, mold, animal protein), and presents with cough and dyspnea of variable acuity. Bronchoalveolar lavage typically shows high relative lymphocyte count (eg, >20%), which helps support the diagnosis.