WBR248

Author	[[PageAuthor::Gerald Chi (Reviewed by Yazan Daaboul, M.D.)]]
Exam Type	ExamType::USMLE Step 1
Main Category	MainCategory::Genetics
Sub Category	SubCategory::Endocrine, SubCategory::Oncology
Prompt	[[Prompt::A newborn male is evaluated for vomiting and failure to pass his first stool within 48 hours of birth. The vomit is approximately two teaspoons in volume, green-brownish in color, without bloody contents. On physical examination, the patient's abdomen is distended, and digital rectal examination elicits massive passage of gas and stools. Diagnosis is made by rectal biopsy that demonstrates lack of migration of ganglions due to mutation of a proto-oncogene. Genetic mutation of the proto-oncogene involved in this patient's condition is also responsible for the development of which of the following clinical manifestations?]]
Answer A	AnswerA::Café au lait macules
Answer A Explanation	[[AnswerAExp::Café au lait macules may be associated with several diseases, including neurofibromatosis type I, McCune–Albright syndrome, tuberous sclerosis, Fanconi anemia, ataxia telangiectasia, Bloom syndrome, Chediak-Higashi syndrome, Gaucher disease, Hunter syndrome, and Wiskott–Aldrich syndrome.]]
Answer B	AnswerB::Cutaneous angiofibroma
Answer B Explanation	AnswerBExp::Angiofibromas are reddish brown papules of 0.1 to 0.3 cm diameter that are typically located over the sides of the nose and the medial portions of the cheeks. Angiofibromas may be assoicated with type 1 multiple endocrine neoplasia.
Answer C	AnswerC::Medullary thyroid carcinoma
Answer C Explanation	[[AnswerCExp::Medullary thyroid cancer is a form of thyroid carcinoma, which originates from the parafollicular cells that produce calcitonin. Approximately 25% of medullary thyroid cancers are genetic in nature, caused by a mutation in the RET proto-oncogene. Medullary thyroid carcinoma may be associated with multiple endocrine neoplasias type 2A and 2B.]]
Answer D	AnswerD::Pituitary prolactinoma
Answer D Explanation	[[AnswerDExp::Pituitary prolactinoma is a benign tumor of the pituitary gland. It is the most common type of pituitary tumor. Symptoms of prolactinoma are either caused by hyperprolactinemia or by pressure of the tumor on surrounding tissues. Prolactinoma and other pituitary tumors may be associated with type 1 multiple endocrine neoplasia.]]
Answer E	AnswerE::Vasoactive intestinal peptide tumor
Answer E Explanation	[[AnswerEExp::A VIPoma is an endocrine tumor usually originating from non-beta islet cells of the pancreas that produce vasoactive intestinal peptide (VIP).The massive amounts of VIP cause profound, chronic watery diarrhea and dehydration, hypokalemia, achlorhydria, vasodilation, hypercalcemia and hyperglycemia. VIPoma may be associated with type 1 multiple endocrine neoplasia.]]
Right Answer	RightAnswer::C
Explanation	[[Explanation::Meconium ileus is characterized by thickening meconium that is congested in the ileum. It is associated with abdominal distension and bilious vomiting that occur soon after birth. Failure of meconsium passage may be associated with either Hirschsprung's disease or cystic fibrosis. GIven that the two diseases may manifest similarly at birth, a rectal biopsy is usually indicated to differentiate between both conditions. During normal fetal development, cells from the neural crest migrate into the colon to form Auerbach's plexus and Meissner's plexus. Hirschsprung's disease (HD) is characterized by incomplete migration of the neural crest cells, which results in the lack of nerve bodies in the distal segments of the colon. The affected segment of the colon cannot relax and pass stool through the colon, and patients typically manifest with meconium ileus after birth. RET is a proto-oncogene that codes for proteins that assist cells of the neural crest in their movement through the digestive tract during the development of the embryo. It encodes a receptor tyrosine kinase for members of the glial cell line-derived neurotrophic factor family of extracellular signalling molecules. Loss-of-function mutations are associated with Hirschsprung's disease, while gain-of-function mutations are associated with medullary thyroid carcinoma, pheochromocytoma, and multiple endocrine neoplasias type 2A and 2B. Educational Objective: RET is a proto-oncogene that codes for proteins that assist cells of the neural crest in their movement through the digestive tract during the development of the embryo. It encodes a receptor tyrosine kinase for members of the glial cell line-derived neurotrophic factor family of extracellular signalling molecules. Loss-of-function mutations are associated with Hirschsprung's disease, while gain-of-function mutations are associated with medullary thyroid carcinoma, pheochromocytoma, and multiple endocrine neoplasias type 2A and 2B. References: Edery P, Lyonnet S, Mulligan LM, et al. Mutations of the RET proto-oncogene in Hirschsprung's disease. Nature. 1994;367(6461):378-80. First Aid 2015 page 337]]
Approved	Approved::Yes
Keyword	WBRKeyword::Men syndromes, WBRKeyword::RET, WBRKeyword::Medullary thyroid cancer, WBRKeyword::MEN syndrome, WBRKeyword::Meconium ileus, WBRKeyword::Hirschsprung's disease
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