A 3-year-old boy presents with failure to thrive, fatty stools, and cholestasis. Laboratory testing reveals severely elevated triglycerides (1200 mg/dL), very low cholesterol (80 mg/dL), and fat-soluble vitamin deficiencies. Genetic testing reveals mutations in the microsomal triglyceride transfer protein (MTP) gene. Which of the following pathophysiologic processes is most directly impaired?
- A)Conversion of cholesterol to pregnenolone
- B)Hepatic cholesterol uptake via LDL receptor
- C)Lipoprotein lipase-mediated hydrolysis of triglycerides
- D)Intestinal cholesterol absorption in the terminal ileum
- E)Apolipoprotein B-100 lipidation and VLDL assemblyGABARITO
Explicação
This patient has abetalipoproteinemia, caused by MTP gene mutations. MTP (microsomal triglyceride transfer protein) is essential for lipidating apoB-100 in hepatocytes (VLDL assembly) and apoB-48 in enterocytes (chylomicron assembly). Without functional MTP, a... Ver explicação completa e trilha adaptativa →