STUDIES IN PORPHYRIA CUTANEA TARDA

迟发性皮肤卟啉病（PCT）是最常见的卟啉病，是由于肝中尿卟啉原脱羧酶的显着缺乏。尿卟啉原脱羧酶缺乏症在PCT发现主要是收购。 本研究的目的如下。 1. 通过测量血清和白色血细胞中的维生素C水平，在标准治疗（重复静脉切开术或低剂量氯喹）前后评估维生素C状态。 这将检验维生素C是肝脏中的抗氧化剂并且其缺乏可能有助于PCT激活的假设。 2. 使用13 C-咖啡因和13 C-美沙西丁呼吸试验以及通过测量咖啡因从血液中的清除率和咖啡因代谢物的尿排泄来体内评估β 1A 2的活性。 3.丙型肝炎感染的作用通过以下方式进行评估：（a）观察通过反复放血或低剂量氯喹治疗PCT对肝功能检查异常和血浆中丙型肝炎抗体和丙型肝炎RNA存在的影响;和（B）观察与未用干扰素x-2 B治疗的患者相比，用干扰素x-2治疗的患者中PCT复发的频率。 标准血清化学以及[13 C]苯丙氨酸呼气试验用于评估肝功能。 干扰素x-2b治疗的适应症将是丙型肝炎患者使用该药物的标准适应症，不受本方案的影响或规定。患者首先接受PCT治疗，因为PCT治疗几乎总是成功的，而丙型肝炎的治疗通常不会成功。

Porphyria cutanea tarda (PCT) is the most common of the porphyrias and is due to a marked deficiency of uroporphyrinogen decarboxylase in liver. The uroporphyrinogen decarboxylase deficiency found in PCT is primarily acquired. The aims of this study are as follows. 1. Vitamin C status is assessed before and after standard treatment (either repeated phlebotomy or low-dose choloroquine) by measuring vitamin C levels in serum and white blood cells. This will test the hypothesis that vitamin C is an antioxidant in the liver and that its deficiency may contribute to activation of PCT. 2. Activity of CYP 1A2 is assessed in vivo using 13C-caffeine and 13C-methacetin breath tests and also by measuring the clearance rate of caffeine from blood and urinary excretion of caffeine metabolites. 3. The role of hepatitis C infection is assessed by (a) observing the effect of treatment of PCT by repeated phlebotomy or low-dose chloroquine on abnormalities in liver function tests and on the presence of hepatitis C antibody and hepatitis C RNA in plasma; and (b) by observing the frequency of recurrence of PCT in patients who are treated with interferon x-2b as compared to patients who are not treated with this drug. Standard serum chemistries as well as a [13C]phenylaline breath test are used to assess liver function. The indications for treatment with interferon x-2b will be the standard indications for use of this drug in patients with hepatitis C and will not be influenced or specified by this protocol. Patients are treated first for PCT, because treatment for PCT is almost always successful, whereas treatment for hepatitis C is usually not.