A 69-year-old man comes to the office with a 6-month history of dry cough and progressive exertional dyspnea. The patient smoked a pack of cigarettes a day for 40 years but quit 15 years ago. He owns 2 parrots and a cat. He feels that his symptoms improved somewhat while on vacation 2 months ago.
On examination, blood pressure is 138/92 mm Hg, pulse is 84/min, and respirations are 18/min. Pulse oximetry is 90% on room air. Chest auscultation shows bilateral crackles with mild end-expiratory wheeze and a 2/6 systolic murmur at the left sternal border. Digital clubbing is present.
Pulmonary function testing shows a restrictive defect with impaired gas exchange. A CT scan of the chest reveals bilateral patchy ground-glass opacities, mostly in the mid-upper lung fields. There is no lymphadenopathy.
Which of the following is the most likely diagnosis?

Question

A 69-year-old man comes to the office with a 6-month history of dry cough and progressive exertional dyspnea.  The patient smoked a pack of cigarettes a day for 40 years but quit 15 years ago.  He owns 2 parrots and a cat.  He feels that his symptoms improved somewhat while on vacation 2 months ago.
On examination, blood pressure is 138/92 mm Hg, pulse is 84/min, and respirations are 18/min.  Pulse oximetry is 90% on room air.  Chest auscultation shows bilateral crackles with mild end-expiratory wheeze and a 2/6 systolic murmur at the left sternal border.  Digital clubbing is present.
Pulmonary function testing shows a restrictive defect with impaired gas exchange.  A CT scan of the chest reveals bilateral patchy ground-glass opacities, mostly in the mid-upper lung fields.  There is no lymphadenopathy.
Which of the following is the most likely diagnosis?

Quizplus · Accepted Answer

11ec193a_98e9_cf77_853d_b1701b008a5a_MD0002_00 Hypersensitivity pneumonitis (HP), also known as extrinsic allergic alveolitis, is a form of interstitial lung disease that develops after inhalation of allergens (microbes, animal/plant proteins, and chemicals). Bird fancier's lung is a form of HP. The presentation may be acute, subacute, or chronic depending on the length of exposure to the antigen. Acute HP occurs within hours of exposure and resolves completely on cessation of exposure. The subacute and chronic forms present with progressively worsening symptoms. However, the subacute form resolves when antigen exposure ceases (with or without corticosteroids). Patients who remain untreated develop interstitial fibrosis and chronic HP. In addition, 50% of patients may have digital clubbing. A history of antigen exposure and cessation of symptoms on removal from the antigenic environment are the major historical clues to diagnosis. Chronic HP is otherwise difficult to distinguish from other causes of pneumonitis. CT scan reveals ground-glass opacities with emphysematous changes in the mid-upper lungs. Workup generally includes inhalation challenge testing. A bronchoalveolar lavage showing lymphocytosis and a lung biopsy showing poorly formed noncaseating granulomas in the lung periphery are usually required for definitive diagnosis. CT scan (Choice A) Chronic obstructive pulmonary disease may also present with chronic cough and exertional dyspnea but shows an obstructive (not restrictive) defect on pulmonary function testing (PFT). (Choice C) Symptoms of idiopathic pulmonary fibrosis are not worsened by exposure to a specific antigen and do not improve after disease onset, unlike in HP. A CT scan may also show honeycombing and traction bronchiectasis. (Choice D) Asthma may present with a chronic cough and worsening of symptoms on exposure to specific environments. However, on CT ground-glass opacities are not present and PFT shows an obstructive defect with normal to increased diffusion capacity of the lung. (Choice E) Ground-glass opacities may be seen in pulmonary sarcoidosis but are usually associated with hilar lymphadenopathy, which is absent in this patient. The noncaseating granulomas of sarcoidosis are more centrally located (around larger airways) as opposed to being more peripherally located in HP. Educational objective: Hypersensitivity pneumonitis (extrinsic allergic alveolitis) is a form of interstitial lung disease that develops after allergen inhalation. It should be suspected in patients who have symptom onset due to specific antigen exposure and resolution of symptoms on cessation of exposure. Chest CT reveals ground-glass opacities. Diagnosis is confirmed with bronchoalveolar lavage and lung biopsy. __________ References: Recent advances in hypersensitivity pneumonitis. (http://www.ncbi.nlm.nih.gov/pubmed/22796841) Hypersensitivity pneumonitis: a historical, clinical, and radiologic review. (http://www.ncbi.nlm.nih.gov/pubmed/19926754) Bird fancier's lung: a state-of-the-art review. (http://www.ncbi.nlm.nih.gov/pubmed/21870048)

A 69-Year-Old Man Comes to the Office with a 6-Month