A 24-year-old man undergoes pulmonary function testing to evaluate dyspnea on exertion. He has no other symptoms except chronic low back pain. The pain is worse at night and improves upon arising and with exercise. He only takes naproxen as needed for back discomfort. He smokes 1 pack of cigarettes per day and drinks a 6-pack of beer each weekend. His erythrocyte sedimentation rate is 77 mm/hr. The following values are obtained: (FEV₁: Forced expiratory volume in 1 second; FVC: Forced vital capacity; FRC: Functional residual capacity)
Which of the following best explains the pulmonary function test findings in this patient?

Question

A 24-year-old man undergoes pulmonary function testing to evaluate dyspnea on exertion. He has no other symptoms except chronic low back pain. The pain is worse at night and improves upon arising and with exercise. He only takes naproxen as needed for back discomfort. He smokes 1 pack of cigarettes per day and drinks a 6-pack of beer each weekend. His erythrocyte sedimentation rate is 77 mm/hr. The following values are obtained:

(FEV₁: Forced expiratory volume in 1 second; FVC: Forced vital capacity; FRC: Functional residual capacity)
Which of the following best explains the pulmonary function test findings in this patient?

Quizplus · Accepted Answer

11ec25c8_d49f_76ac_bc81_9d8690414c08_MD0003_00 Chronic low back pain in an otherwise young healthy man, pain at night, improvement of pain with activity, and elevated erythrocyte sedimentation rate are suggestive of ankylosing spondylitis (AS). AS is a chronic inflammatory disease of the axial skeleton characterized by progressive stiffness of the spine, sacroiliitis on radiographs, and positive serology for HLA-B27 in the majority of patients. Some patients also develop extraarticular features, such as anterior uveitis, inflammatory bowel disease, and cardiac involvement with aortic regurgitation. Patients with AS can develop limitations in lung expansion due to diminished chest wall and spinal mobility. Pulmonary function tests (PFT) may reveal a mildly restrictive pattern with reduced vital capacity (VC) and total lung capacity (TLC) but normal FEV₁/FVC ratio. Functional residual capacity (FRC) and residual volume (RV) are normal or increased due to fixation of the rib cage in an inspiratory position. Pulmonary function tests (PFT) (Choice B) Patients with AS may occasionally develop pulmonary fibrosis, which also causes a restrictive pattern with reduced FVC and FEV₁ and a normal or increased FEV₁/FVC ratio. However, FRC, TLC, and RV are also reduced. (Choices C and E) PFT in patients with obstructive lung disease typically reveals a reduced FEV₁ (<80% of predicted) and FEV₁/FVC (<70%) ratio. This patient's PFTs are more consistent with restrictive lung disease. (Choice D) Pulmonary hypertension can develop as a result of long standing obstructive or severe restrictive lung disease. Patients with idiopathic pulmonary arterial hypertension can have a mild decrease in FEV₁ or FVC; however, the lung volumes are usually normal. Educational objective: Patients with ankylosing spondylitis can develop restrictive lung disease due to diminished chest wall and spinal mobility. Pulmonary function tests show a mildly restrictive pattern with reduced vital capacity and total lung capacity but normal FEV₁/FVC. References: Restrictive pulmonary function is more prevalent in patients with ankylosing spondylitis than in matched population controls and is associated with impaired spinal mobility: a comparative study. (http://www.ncbi.nlm.nih.gov/pubmed/22277377) Pulmonary function and maximal transrespiratory pressures in ankylosing spondylitis. (http://www.ncbi.nlm.nih.gov/pubmed/2782973)

A 24-Year-Old Man Undergoes Pulmonary Function Testing to Evaluate Dyspnea