A 64-year-old man comes to the office complaining of a progressive, dry cough and worsenin… — USMLE Step 2 CK

A $64$ -year-old man comes to the office complaining of a progressive, dry cough and worsening shortness of breath upon exertion for the past $4$ months. He has a $12$ -year history of seropositive rheumatoid arthritis, currently treated with weekly methotrexate and daily folic acid. He also takes over-the-counter ibuprofen for occasional joint pain. He has a $25$ -pack-year smoking history but quit $5$ years ago. Vital signs show a temperature of $37.0^\circ\text{C}$ ( $98.6^\circ\text{F}$ ), blood pressure of $128/82\text{ mm Hg}$ , pulse of $84\text{/min}$ , and respiratory rate of $18\text{/min}$ . Pulse oximetry is $94\%$ on ambient air. Physical examination shows bilateral ulnar deviation and metacarpophalangeal joint subluxation. Lung auscultation reveals fine, end-inspiratory crackles prominently at both lung bases. There is no wheezing. Cardiovascular examination shows a regular rate and rhythm with no murmurs, gallops, or jugular venous distention. There is no lower extremity edema. Laboratory studies reveal an erythrocyte sedimentation rate of $45\text{ mm/h}$ and a normal complete blood count. A plain chest radiograph obtained in the clinic shows bilateral, fine reticular opacities at the lung bases.

Which of the following is the most appropriate next step in the management of this patient's respiratory symptoms?

A
Initiation of a long-acting muscarinic antagonist and inhaled corticosteroid
B
Administration of intravenous furosemide and fluid restriction
High-resolution computed tomography of the chestAnswer
D
Empiric initiation of oral azithromycin and amoxicillin-clavulanate
E
Measurement of serum thyroid-stimulating hormone and free thyroxine levels

Answer

High-resolution computed tomography of the chest

The correct answer is high-resolution computed tomography of the chest. This patient's progressive exertional dyspnea, dry cough, fine end-inspiratory crackles, and reticular opacities on chest radiography are highly characteristic of interstitial lung disease (ILD). Patients with rheumatoid arthritis are at significant risk for developing ILD as a direct extra-articular manifestation of the disease itself, or as a rare but severe pulmonary toxicity from disease-modifying antirheumatic drugs (DMARDs) such as methotrexate. Because plain chest radiography lacks the sensitivity and specificity to adequately evaluate the lung parenchyma, high-resolution computed tomography (HRCT) of the chest is the diagnostic modality of choice to confirm the presence of ILD, characterize its specific radiologic pattern (e.g., usual interstitial pneumonia), and determine the extent of lung involvement.

Step-by-Step Solution

Analyze the patient's clinical presentation and medical history.

The patient has progressive dyspnea, a dry cough, and basilar crackles, in the setting of long-standing rheumatoid arthritis and methotrexate use.

To identify the most likely underlying pathophysiological process driving the symptoms.

Interpret the physical exam and initial imaging findings.

Fine end-inspiratory crackles and reticular opacities on chest radiography strongly suggest interstitial lung disease (ILD). The absence of wheezing, fever, or signs of volume overload rules out COPD, pneumonia, and heart failure.

To narrow the differential diagnosis and exclude common pulmonary or cardiac exacerbations.

Determine the optimal diagnostic test for the suspected condition.

High-resolution computed tomography (HRCT) of the chest is selected as the most appropriate next step.

HRCT is the gold standard imaging modality for diagnosing, characterizing, and determining the extent of ILD.

Key Concept

Interstitial lung disease is a serious extra-articular complication of rheumatoid arthritis and a potential adverse effect of methotrexate therapy. High-resolution computed tomography (HRCT) of the chest is the most appropriate next step for definitive diagnosis when clinical and radiographic findings suggest the condition.

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