A 37-year-old Caucasian man presents with a several-month history of intermittent fevers, chills, chest tightness, and shortness of breath. The episodes typically occur on weekends and are most pronounced in the afternoon with improvement by the morning. He is a lawyer in California and does not smoke. He has no pets, has not traveled outside the country recently, and has had no sick contacts over this period. His father recently had a stroke, so the patient helps him manage his farm on the weekends. The patient has a temperature of 37.2°C, blood pressure of 128/84 mmHg, heart rate of 82 beats per minute, respiratory rate of 16 breaths per minute, and oxygen saturation of 99% on room air. His physical examination is unremarkable. A chest x-ray is normal, and the patient elects to undergo lung biopsy that reveals multiple noncaseating interstitial granulomas.
What is the most likely diagnosis?a. Chronic obstructive pulmonary disease
Hypersensitivity pneumonitis. The temporal relationship of symptoms during weekends, along with the history of visiting a farm on weekends, suggests hypersensitivity pneumonitis as the diagnosis. There are three forms of the disease: acute, subacute, and chronic. This patient likely has the acute form, which presents with symptoms such as fevers, chills, chest tightness, and dyspnea usually 4 to 6 hours after exposure to the organic dust (compared to inorganic dusts in pneumoconiosis). “Farmer’s lung” is one of the most common causes of hypersensitivity pneumonitis and is caused by a variety of agents (e.g., thermophilic actinomycetes). Other important exposures that may cause hypersensitivity pneumonitis include birds and other animals, plant products from lumber milling, and ventilation sources. The most important treatment is avoidance of exposure to the etiologic antigen.
Hypersensitivity pneumonitis is distinct from the other environmental exposures termed pneumoconiosis. Important pneumoconiosis include asbestosis (shipbuilders, textile workers, construction workers with pleural plaques and increased risk of cancer), silicosis (miners, sand blasters with eggshell calcifications and increased risk of TB and cancer), berylliosis (machine and metal workers with a chronic granulomatous disease that mimics sarcoidosis), and coal worker’s pneumoconiosis (nodularity like silicosis with risk for massive pulmonary fibrosis).
(A) This patient has no history of smoking and has intermittent symptoms with a normal chest x-ray, making COPD a less likely diagnosis. (B) Sarcoidosis is a granulomatous disease most commonly affecting the lungs, and noncaseating granulomas would be seen on biopsy; however, the intermittent nature of the symptoms does not fit with sarcoidosis. Bilateral hilar lymphadenopathy is also frequently seen on chest x-ray. (D) Silicosis is caused by inhalation of silica, which is not suggested by this patient’s occupational history. (E) Coccidioidomycosis is caused by the dimorphic fungus Coccidioides immitis. There would be no temporal relationship of the symptoms to weekends with this infection. There is no exposure history that is suggestive of tuberculosis.