SHM Converge Scientific Abstract ePoster Gallery-Amiodarone-Induced Pneumonitis: Refining Base Rate

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This case highlights the importance of refining disease base rates to the individual patient when interpreting diagnostic tests. A man in his 50s with heart failure and atrial fibrillation presented with subacute worsening dyspnea, hypoxemia, crackles, and diffuse airspace opacities on chest X-ray, initially raising concern for heart failure. However, he lacked typical signs of volume overload, such as edema or elevated JVP, and there were no clear triggers for isolated pulmonary edema.<br /><br />Chest CT showed diffuse ground-glass opacities and consolidations. Workup for infection and autoimmune disease was largely negative, except for a low-to-moderate positive C-ANCA, which raised concern for ANCA-associated vasculitis (AAV). The differential also included amiodarone-induced pneumonitis (AIP) and atypical infection. Importantly, the patient had been taking amiodarone 600 mg daily for six months, a dose associated with a much higher risk of pulmonary toxicity. While AAV and AIP are both rare in the general population, the patient’s amiodarone exposure substantially increased the pre-test probability of AIP. This demonstrates how base rates must be adjusted for patient-specific risk factors rather than relying only on general population prevalence.<br /><br />Bronchoalveolar lavage showed lymphomonocytic cellularity with foamy macrophages, and microbiologic studies were negative, supporting AIP. Amiodarone was discontinued and prednisone was started with a taper. His dyspnea and hypoxemia improved within days, and follow-up CT at six months showed resolution of the abnormalities. He remained asymptomatic at two years.<br /><br />Key lessons: consider amiodarone lung toxicity in patients with respiratory symptoms, especially at doses of 400 mg/day or more; avoid anchoring bias on chronic illnesses like heart failure; and interpret positive tests in the context of individualized disease probability.

Asset Subtitle

Zaven Sargsyan

Meta Tag

Author List Zaven Sargsyan

Category Clinical Vignettes

Concept Amiodarone-induced pulmonary toxicity

Concept Dyspnea

Concept Hypoxemia

Concept Diffuse lung infiltrates

Concept Amiodarone

Distinguished Non-Finalist

Presenter Organization Baylor College of Medicine

Presenting Author Zaven Sargsyan

Track Adult

Keywords

amiodarone-induced pneumonitis

base rate adjustment

diagnostic interpretation

heart failure

atrial fibrillation

ground-glass opacities

C-ANCA

bronchoalveolar lavage

pulmonary toxicity

hypoxemia

Amiodarone-induced pulmonary toxicity

Dyspnea

Hypoxemia

Diffuse lung infiltrates

Amiodarone