The patient presents with symptoms consistent with emphysema, and his young age of presentation and absent smoking history suggest it is due to genetic alpha1-antitrypsin deficiency.
Antitrypsin functions as a inhibitor of elastase (a degrader of elastin). Elastin is an essential protein in the lung provided proper recoil of the lung during exhalation. A deficiency of antitrypsin results in the increased activity of elastase, released by macrophages and neutrophils, leading to the destruction of the alveolar sacs. This leads to decreased elastic recoil and decreased radial traction, causing increased lung volume (hyperinflation) and air trapping (obstruction).
Hunter et al. state that emphysema exacerbations can have several causes, including patient non-compliance with medications, exposure to pollutants, and, most commonly, infection (bacterial or viral). For these exacerbations, treatment options include bronchodilators, anticholinergics, and oxygen therapy.
Kazuhiro et al. note the major finding in emphysema is damage to the lung parenchyma, but the extent is often age dependent. The authors note that as a patient ages, lung functioning naturally decreases due to increased oxidative stress, inflammation, and exposure to pollutants.
Image A shows an increased A-P diameter, a finding seen in patients with emphysema. It is the result of the increased TLC of the patient's lung due to destruction of the alveolar spaces.
Illustration A shows typical lung findings of patients with emphysema. Note the enlarged air spaces from unbalanced protease activity.
Answer 1: Though the spirometry values are consistent with an obstructive disease, chronic bronchitis is not consistent with the patient's other symptoms (lack of sputum, increased A-P diameter).
Answer 3: Pneumothorax, air within the pleural space, is not seen on the imaging provided and PFT's would likely show a decreased TLC if performed.
Answer 4: Though asthma is an obstructive disease, the patient's presentation is not consistent with an asthma exacerbation (wheezing, reversible nature, etc).
Answer 5: Hypersensitivity pneumonitis would more commonly produce restrictive PFT values (normal/increased FEV1/FVC, decreased TLC).
Hunter MH, King DE. COPD: management of acute exacerbations and chronic stable disease. Am Fam Physician. 2001 Aug 15;64(4):603-12
PMID:11529259 (Link to Abstract)
Ito K, Barnes PJ. COPD as a disease of accelerated lung aging. Chest. 2009 Jan;135(1):173-80
PMID:19136405 (Link to Abstract)