每日一题_2023.08.10

A 14-year-old high school freshman presents to her family doctor for a sports physical. She has not played organized sports in the past but is in good physical shape. She mentions that she experienced severe leg cramps after trying out for the soccer team last week. The night after the tryouts, she noticed that her urine had a reddish tinge. She has no other medical com- plaints. Her physician orders an ischemic fore- arm exercise test, which reveals no increase in venous lactate. Which of the following enzymes is most likely deficient in this patient?

一个14岁的高中新生因进行体育体检而前往家庭医生。她过去没有参加过有组织的体育活动，但身体状况良好。她提到上周在尝试加入足球队后出现了严重的腿部抽筋。尝试后的那个晚上，她注意到她的尿液带有红色。她没有其他医疗问题。她的医生下令进行缺血性前臂运动试验，结果显示静脉乳酸没有增加。以下哪种酶在这名患者身上最有可能缺乏？

(A) a-1,6-Glucosidase

(B) Cystathionine synthase

(C) Glucose-6-phosphatase

(D) Glycogen phosphorylase

(E) Lysosomal a-1,4-glucosidase

答案解析：

该患者患有麦卡德尔病，这是一种糖原贮积症，肌内糖原磷酸化酶缺乏。这种酶负责从糖原分子的分支中释放单个葡萄糖-1-磷酸单位。该病通常在青春期或成年早期发病，以肌肉痉挛、快速疲劳和体力活动时耐力差为特征。在一些患者中也观察到严重的肌红蛋白尿。

正确答案：D