慢性C型肝炎(Chronic hepatitis C) 患者可能出現相關肝外疾病（extrahepatic manifestations）。 隨醫療日益普及進步，越來越多疾病被發現與C型肝炎相關連。本文回顧文獻，探討C型肝炎 與脂肪肝（hepatic steatosis, fatty liver）的關連性，進一步提及與胰島素抗性（insulin resistance）、第二型糖尿病（type 2 diabetes mellitus，以下本文糖尿病皆指第二型）的關係。慢性C型肝炎與脂肪肝建立關係的機轉有多篇文獻提出，主要是C型肝炎病毒核心蛋白影響肝細胞的脂肪代謝，使脂肪囤積於肝細胞，導致脂肪肝。而經機轉解釋或實際觀察結果都可發現，治療慢性C型肝炎可使脂肪肝獲得改善。慢性C型肝炎患者易發生胰島素抗性，相關機轉牽涉多項病毒與宿主因素，控制不佳容易發展糖尿病及脂肪代謝問題。慢性C型肝炎患者伴隨胰島素抗性者會加速其肝硬化。胰島素抗性使C型肝炎治療成效不彰。於治療C型肝炎前或同步控制胰島素抗性（生活調整或藥物介入）有些患者可獲較佳的效果。在為慢性C型肝炎患者追蹤治療時，應注意有否發生相關疾病，若發現須一併控制。

Patients with chronic hepatitis C may have extrahepatic manifestations. As medicine science improves and medical service is more available, more diseases are found having relationship to hepatitis C. I reviewed journals
and discussed the relationship and possible mechanisms between hepatitis C and hepatic steatosis, insulin resistance and type 2 diabetes mellitus. Hepatitis C core protein influences lipid metabolism in liver cell, so lipid accumulates in liver cell, then causes hepatic steatosis. Treating hepatitis C makes hepatic steatosis recovery. Patients with chronic hepatitis C often have insulin intolerance and often develop type 2 diabetes mellitus. Chronic hepatitis C combines with insulin resistance make hepatic cirrhosis worse. Insulin resistance impairs response of interferon treatment for hepatitis C. To control insulin resistance before or during treatment for hepatitis C with life modification or using some medicines enhance sustained virological response. Beware the relate diseases when we care patients with chronic hepatitis C, control them if they develop.