A 33-year-old woman comes to the office due to worsening exertional dyspnea. She previously jogged frequently, but now becomes short of breath while walking her dog in the park. The patient has no other significant medical history and takes no medications. She smokes a pack of cigarettes daily and does not use alcohol or illicit drugs. Blood pressure is 124/76 mm Hg, pulse is 78/min, and respirations are 20/min. BMI is 27 kg/m². Cardiac examination is unremarkable. Laboratory studies reveal markedly decreased serum alpha-1 antitrypsin levels. Which of the following pulmonary function test patterns is most likely to be present in this patient?

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11ec160b_3b29_827c_9249_31f0357b623a_MD0001_00 This young woman with progressively worsening dyspnea, history of cigarette smoking, and decreased serum levels of alpha-1 antitrypsin (AAT) likely has AAT deficiency and associated early-onset emphysema. Emphysema from any cause leads to increased total lung capacity as the lungs hyperinflate, decreased FEV1/FVC ratio, and decreased DLCO (diffusing capacity for carbon monoxide) due to destruction of alveoli and adjoining capillary beds. AAT is a protein that inhibits several proteolytic enzymes released by inflammatory cells (particularly neutrophil elastase), thereby reducing tissue damage from the inflammatory cascade. Even in the absence of smoking, patients with AAT deficiency typically develop early-onset emphysema (prior to age 50) due to the body's inability to inhibit tissue proteolysis. Cigarette smoking and the associated pulmonary inflammation that it induces can greatly accelerate the development of emphysema in these patients. The emphysema in AAT deficiency typically develops in a panacinar pattern. (Choice A) Obstructive lung disease causes increased lung volumes (residual volume and total lung capacity) and decreased FEV1/FVC ratio, but the DLCO can vary based on etiology. Asthma is an obstructive disease that can have high DLCO due to increased pulmonary capillary blood volume and intact alveolar-arterial membranes (lack of emphysematous destruction). (Choice C) The pattern of decreased FEV1/FVC ratio, decreased lung volume, and decreased DLCO reflects combined restrictive and obstructive defects, which can be due to multiple diseases present simultaneously or diseases such as pneumoconiosis (eg, silicosis, asbestosis) and sarcoidosis. (Choice D) Reduced FEV1/FVC ratio and normal DLCO may occur in asthma or in chronic bronchitis-predominant chronic obstructive pulmonary disease. (Choices E and F) Restrictive lung disease can be categorized according to intrinsic (eg, interstitial lung disease) and extrinsic (eg, obesity, neuromuscular disease) etiologies, both of which demonstrate a pattern of reduced lung volumes with normal or increased FEV1/FVC ratio (although both the FEV1 and FVC are reduced individually). The DLCO helps distinguish between the 2 forms: Intrinsic restrictive lung disease demonstrates reduced DLCO, whereas extrinsic disease has normal DLCO. Educational objective: Emphysema most commonly results from chronic smoking but can also occur in genetically predisposed individuals with alpha-1 antitrypsin deficiency. Patients with emphysema have a decreased forced expiratory volume in 1 second/forced vital capacity ratio, increased total lung capacity, and decreased diffusing capacity. __________ References: A stepwise approach to the interpretation of pulmonary function tests. (http://www.ncbi.nlm.nih.gov/pubmed/24695507)

A 33-Year-Old Woman Comes to the Office Due to Worsening