A 72-year-old man comes to the clinic reporting a 6-week history of progressively worsenin… — USMLE Step 2 CK

A $72$ -year-old man comes to the clinic reporting a $6$ -week history of progressively worsening shortness of breath, a dry cough, and generalized fatigue. He has a history of paroxysmal atrial fibrillation and a myocardial infarction $3$ years ago. His daily medications include apixaban, amiodarone, metoprolol succinate, and atorvastatin. Vital signs show a temperature of $37.1^\circ\text{C}$ ( $98.8^\circ\text{F}$ ), blood pressure of $128/78\text{ mm Hg}$ , and pulse of $64\text{/min}$ . Oxygen saturation is $92\%$ on room air. Jugular venous pressure is $6\text{ cm H}_2\text{O}$ . Cardiac auscultation reveals a regular rate and rhythm with no murmurs, rubs, or gallops. Pulmonary examination reveals fine bilateral inspiratory crackles but no wheezing. Laboratory studies reveal:

- Leukocyte count: $7,200/\text{mm}^3$
- Brain natriuretic peptide (BNP): $85\text{ pg/mL}$ (normal $< 100\text{ pg/mL}$ )
- Thyroid-stimulating hormone (TSH): $7.2\text{ }\mu\text{U/mL}$ (normal: $0.4\text{--}4.0\text{ }\mu\text{U/mL}$ )
- Free $T_4$ : $1.8\text{ ng/dL}$ (normal: $0.9\text{--}1.7\text{ ng/dL}$ )

High-resolution computed tomography of the chest demonstrates bilateral ground-glass opacities and focal areas of consolidation. Which of the following is the most appropriate next step in management?

Discontinue amiodarone and initiate systemic glucocorticoid therapyAnswer
B
Administer intravenous furosemide and schedule an echocardiogram
C
Initiate empiric treatment with oral levofloxacin
D
Initiate oral levothyroxine supplementation
E
Initiate oral citalopram therapy

Answer

Discontinue amiodarone and initiate systemic glucocorticoid therapy

This patient's progressive dyspnea, dry cough, bilateral crackles, and ground-glass opacities on high-resolution computed tomography (HRCT) are highly suggestive of amiodarone-induced pulmonary toxicity (APT). APT is a life-threatening adverse effect of amiodarone, a widely used Class III antiarrhythmic. It typically presents as a subacute interstitial pneumonitis. The normal jugular venous pressure and normal brain natriuretic peptide (BNP) levels help differentiate this condition from cardiogenic pulmonary edema. Because amiodarone is highly lipophilic and tissue-bound, its terminal elimination half-life can exceed

100

days. Therefore, in symptomatic patients with evidence of widespread lung injury, simply discontinuing the drug is insufficient. The standard of care requires immediate cessation of amiodarone combined with the initiation of systemic glucocorticoids (e.g., prednisone) for several months to suppress the inflammatory cascade while the drug is slowly eliminated from the body.

Step-by-Step Solution

Analyze the clinical presentation and imaging.

The patient has subacute dyspnea, dry cough, inspiratory crackles, and ground-glass opacities on HRCT.

These findings characterize an interstitial lung process, not an obstructive or purely airway-based disease.

Differentiate between cardiogenic and non-cardiogenic causes of pulmonary infiltrates.

The normal BNP (

85\text{ pg/mL}

) and normal jugular venous pressure (

6\text{ cm H}_2\text{O}

) effectively rule out cardiogenic pulmonary edema.

A history of myocardial infarction increases the risk for heart failure, but current objective markers do not support fluid overload.

Evaluate the medication list for potential etiologies.

The patient takes amiodarone, a Class III antiarrhythmic known to cause potentially fatal pulmonary toxicity (interstitial pneumonitis).

Amiodarone pulmonary toxicity correlates perfectly with the clinical and radiographic findings.

Determine the definitive treatment for the identified condition.

Management requires immediate discontinuation of amiodarone and the initiation of systemic glucocorticoids.

Because amiodarone is highly lipophilic and has a very long half-life (up to several months), simply stopping the medication is often insufficient in symptomatic patients; steroids are needed to suppress the inflammatory response and accelerate recovery.

Key Concept

Management of amiodarone-induced pulmonary toxicity

Estimated Time:1m 30s

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