Practice question from A Step-style clinical vignette requiring diagnosis or management based on symptoms and lab findings. USMLE
A 35-year-old woman presents with recurrent episodes of flushing, diarrhea, and wheezing. 24-hour urine 5-HIAA is markedly elevated. CT shows multiple liver lesions and a small bowel mass. Which complication requires monitoring with echocardiography? A. Dilated cardiomyopathy from chronic tachycardia B. Coronary artery vasospasm from serotonin C. Right-sided valvular fibrosis (tricuspid and pulmonary) D. Left-sided valvular regurgitation from prostaglandin release E. Pericardial effusion from metastatic disease
Answer
C
Explanation
This is carcinoid syndrome (small bowel carcinoid tumor with liver metastases causing systemic symptoms from serotonin release). Carcinoid heart disease occurs in 50% of patients with carcinoid syndrome, characterized by RIGHT-sided valvular fibrosis (plaque-like endocardial thickening) affecting tricuspid and pulmonary valves. Serotonin and other vasoactive substances are metabolized by the lungs, so left-sided valves are typically spared unless there's a right-to-left shunt. Dilated cardiomyopathy, vasospasm, and left-sided disease are not typical. Pericardial effusion is not a specific complication of carcinoid.