General Pathology USMLE Step 1 Practice Question
A 17-year-old boy undergoing screening colonoscopy for familial polyposis presents with hundreds of adenomatous polyps throughout the colon. Vital signs are normal (BP 118/76, HR 72, RR 16, Temp 37°C). His father underwent colectomy in his twenties for identical pathology. Laboratory studies show normal hemoglobin and no occult blood in stool currently. Which molecular abnormality most likely initiates the earliest step in his polyp development?
Answer choices
- AInactivation of VHL with increased HIF activity
- BLoss of APC leading to accumulation of beta cateninCorrect answer
- CAmplification of HER2 on chromosome 17
- DActivation of BCL2 preventing apoptosis
- EMutation of JAK2 causing constitutive tyrosine kinase activity
- FBiallelic inactivation of TP53 leading to loss of the DNA damage checkpoint
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