This patient's presentation is consistent with a diagnosis of carcinoid syndrome. Elevated 24 hour urine levels of 5-hydroxyindoleacetic acid (5-HIAA) are diagnostic of carcinoid syndrome.
The GI tract is a common location for carcinoid tumors; however, carcinoid syndrome does not manifest until the tumor has metastasized to the liver or outside the GI tract, allowing for the released serotonin to escape hepatic degradation. Common presenting symptoms of carcinoid syndrome include flushing, diarrhea, tachycardia/hypotension, bronchospasm, telangiectasia, and right-sided heart failure. The right-sided heart disease of carcinoid syndrome involves endocardial plaques and fibrous intimal thickening, resulting in pulmonic stenosis, tricuspid insufficiency, and possibly restrictive cardiomyopathy.
Moerman et al. discuss the typical findings of carcinoid syndrome on echocardiography and cardiac MRI. Echo demonstrates thickening of leaflets and valvular insufficiency of both the tricuspid and pulmonic valves, ultimately leading to right heart failure. Cardiac MRI can visualize deposition of fibrous plaque on the walls of the right ventricle and can also be used to assess dilatation of the right ventricle.
Robertson et al. review the presentation, diagnosis, treatment, and prognosis of carcinoid tumors. Presentation of carcinoid tumors can be highly variable, ranging from asymptomatic to a more classic presentation, as in the above vignette. Carcinoid syndrome appears in only 10% of patients with carcinoid tumors and commonly does not present until the tumor has metastasized to the liver or lungs. Diagnosis centers around urine analysis for 5-HIAA, serum levels of Chromogranin A, radiographic imaging, and nuclear medicine scans targeting somatostatin receptors using radiolabeled octreotide.
Illustration A summarizes the clinical manifestations of carcinoid syndrome.
Illustration B depicts the right sided heart disease associated with carcinoid syndrome; note the deposition of plaques on the walls of the right ventricle, tricuspid insufficiency, and the stenosis of the pulmonic valve.
Answer 1: Carcinoid syndrome is associated with elevated levels of chromogranin A.
Answer 2: If the diarrhea associated with carcinoid syndrome was severe, metabolic acidosis (not alkalosis) would be expected due to loss of alkaline material.
Answer 3: Elevated urinary VMA would be expected in neuroblastoma or pheochromocytoma; VMA is a metabolite of epinephrine and norepinephrine.
Answer 4: If the diarrhea associated with carcinoid syndrome was severe, hypokalemia might be expected.
Robertson RG, Geiger WJ, Davis NB. Carcinoid tumors. Am Fam Physician. 2006 Aug 1;74(3):429-34.
PMID:16913162 (Link to Abstract)
Moerman VM, Dewilde D, Hermans K. Carcinoid heart disease: typical findings on echocardiography and cardiac magnetic resonance. Acta Cardiol. 2012 Apr;67(2):245-8.
PMID:22641985 (Link to Abstract)
USMLE World Step 1 QBank Question #74. Copyright © USMLEWorld, LLC 2012