WBR0215

Author	PageAuthor::Vendhan Ramanujam
Exam Type	ExamType::USMLE Step 2 CK
Main Category	MainCategory::Internal medicine
Sub Category	SubCategory::Endocrine, SubCategory::Preventive Medicine, SubCategory::Genetics
Prompt	[[Prompt::A 35 year old Caucasian male is diagnosed with medullary thyroid carcinoma that is non resectable. His past medical history is insignificant. He does not smoke or consume alcohol. His family history is significant for thyroid cancer and pheochromocytoma in his father. Which of the following could have been most effective in preventing this patient’s non resectable cancer?]]
Answer A	AnswerA::Frequent neck examinations
Answer A Explanation	AnswerAExp::'''Incorrect'''-Frequent neck examinations is not sensitive enough to diagnose early medullary thyroid carcinoma.
Answer B	AnswerB::Annual physical examination
Answer B Explanation	AnswerBExp::'''Incorrect'''-Annual physical examination are not sensitive enough to diagnose early medullary thyroid carcinoma.
Answer C	AnswerC::Periodic calcium measurement
Answer C Explanation	AnswerCExp::'''Incorrect'''-Periodic calcium measurement is useful for screening patients with parathyroid hyperplasia in MEN I and MEN IIa.
Answer D	AnswerD::Periodic stimulated serum calcitonin measurement
Answer D Explanation	[[AnswerDExp::Incorrect-Periodic stimulated serum calcitonin measurement was previously used to diagnose early medullary thyroid carcinoma before the advent of genetic tests. It is a labor intensive and time consuming test. It is still used to identify residual medullary thyroid carcinoma after thyroidectomy.]]
Answer E	AnswerE::DNA testing
Answer E Explanation	[[AnswerEExp::Correct-The patient has features suggestive of MEN IIa, which is characterized by medullary thyroid carcinoma, pheochromocytoma as well as parathyroid hyperplasia. It is an autosomal dominant disorder arising from mutation in RET proto-oncogene localized in chromosome 10. Genetic testing can be easily carried out in peripheral blood sample by a sensitive PCR method that will identify the mutations. More than 95% have RET proto-oncogene mutation.]]
Right Answer	RightAnswer::E
Explanation	[[Explanation::The patient has features suggestive of MEN IIa, which is characterized by medullary thyroid carcinoma, pheochromocytoma as well as parathyroid hyperplasia. It is an autosomal dominant disorder arising from mutation in RET proto-oncogene localized in chromosome 10. Genetic testing can be easily carried out in peripheral blood sample by a sensitive PCR method that will identify the mutations. More than 95% have RET proto-oncogene mutation. A positive test will recommend a total thyroidectomy to prevent the development of an invasive medullary carcinoma, which is close to 100%. Educational objective: In suspected MEN IIa, genetic testing has replaced serum calcitonin measurement as the recommended screening test for early diagnosis of medullary thyroid carcinoma. A total thyroidectomy is indicated after the diagnosis. Educational Objective: References: ]]
Approved	Approved::Yes
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