95 一位 73 歲男性數度發生呼吸困難，並出現心包囊及肋膜腔積水，影像學檢查發現肝腫大充血，尿中 5-hydroxyindoleacetic acid 為 40 mg/24 小時（正常值為 0.7-8.2 mg/24 小時）。病人後來接受肺動脈瓣 及三尖瓣置換手術，下列敘述中何者最符合此病人右心瓣膜的病理變化？
(A) Deposition of mucoid material in spongiosa
(B) Calcification and fibrosis at the base of valves
(C) Plaque-like intimal thickening and smooth muscle cell proliferation
(D) Subendocardial accumulation of elastic fibers

5-Hydroxyindoleacetic acid (5-HIAA) is the main metabolite of serotonin.

Carcinoid tumors elaborate bioactive products (e.g.,serotonin, kallikrein, bradykinins, histamine, prostaglandins,and tachykinins P and K) that can cause cardiac lesions. The precise agent responsible is uncertain, although it is presumably rapidly etabolized in lung and liver, because cardiac lesions do not occur unless there is extensive hepatic metastatic spread. Right-sided heart lesions (valvular and endocardial) predominate.

• Lesions are characterized by plaque-like intimal thickening (composed of smooth muscle cells and associated ECM) of the tricuspid and pulmonary valves and right ventricular outflow tract; left-sided lesions are uncommon except in primary pulmonary carcinoids.

• Tricuspid insufficiency and pulmonic stenosis are the typical valvular consequences.

• Similar lesions occur in the setting of drugs that have sero-toninergic effects (e.g., methylsergide, ergotamine, some antiparkinsonian medications, and fenfluramine , appetite suppressant combination with phentermine]).