WBR0309

Author	[[PageAuthor::Yazan Daaboul, M.D. (Reviewed by Serge Korjian)]]
Exam Type	ExamType::USMLE Step 1
Main Category	MainCategory::Pathology
Sub Category	SubCategory::Renal
Prompt	[[Prompt::A 42-year-old woman presents to the physician's office for headache and blurry vision for the past 2 days. Further questioning reveals the patient is previously healthy, takes no medications, and has never been hospitalized. She reports that her blood pressure has recently been elevated on several occasions at different times during the day. Physical examination is unremarkable. Her heart rate is 82/min, blood pressure is 172/90 mmHg, and temperature is 36.1 ᵒC (97 ᵒF), a. Work-up reveals small stenoses along the mid to distal left renal artery on angiography with areas of small aneurysms causing a "string of beads" appearance. An image of her CT angiography scan is shown below. What is the most likely diagnosis? Courtesy of www.radiopaedia.org]]
Answer A	AnswerA::Takayasu arteritis
Answer A Explanation	[[AnswerAExp::Takayasu arteritis is a chronic inflammatory disease of the large arteries, such as the proximal aorta and its large branches. It is common in young women. Pathogenesis of Takayasu arteritis is the granulomatous formation and fibrosis, especially in the medial layer of the arterial wall. Although a large number of patients with vasculitis do not show any increase in inflammatory markers, classically vasculitis is still considered a systemic inflammation with elevated acute phase reactants. "String of beads" appearance is not seen on CT scan in patients with Takayasu arteritis.]]
Answer B	AnswerB::Renal artery stenosis
Answer B Explanation	[[AnswerBExp::Renal artery stenosis is a common cause of secondary hypertension. It is an atherosclerotic condition that eventually leads to renal failure due to renal hypoxia and inadequate nutrition of renal parenchymal cells caused by the stenotic artery. Atherosclerosis in the renal artery is almost always seen in the proximal to mid portion; in contrast to FMD which mostly occupies the mid to distal regions. "String of beads" appearance is not seen on CT scan in patients with renal artery stenosis.]]
Answer C	AnswerC::Fibromuscular dysplasia
Answer C Explanation	AnswerCExp::Although FMD may be an incidental finding, it may present with hypertension due to alteration in renal hemodynamics. On CT scan, a "string of beads" appearance is present in the mid to distal portions of the renal artery.
Answer D	AnswerD::Secondary hyperaldosteronism
Answer D Explanation	AnswerDExp::Although secondary hyperaldosteronism may be a cause of secondary hypertension, the patient's findings are not consistent with secondary hyperaldosteronism.
Answer E	AnswerE::Pheochromocytoma
Answer E Explanation	AnswerEExp::Pheochromocytoma is also a cause of secondary hypertension in young patients. However, CT scan in pheochromocytoma typically shows a mass in the adrenal glands. Renal artery involvement is not likely in pheochromocytoma.
Right Answer	RightAnswer::C
Explanation	[[Explanation::Fibromuscular dysplasia (FMD) is a non-atherosclerotic, non-inflammatory vascular disease that most commonly involves the medium-size arteries, especially renal and carotid arteries. Nonetheless, the involvement of almost all arterial beds has been already described in the literature. Generally, it accounts for only 1% of cases of arterial stenosis. FMD may be an incidental finding, but patients may present with symptoms of hypertension due to alteration in renal hemodynamics. Although FMD has been associated with several conditions, such as smoking, hypertension, and hormonal dysregulation, the real cause of FMD is still unknown. FMD is caused by fibroplasia of any layer of the arterial wall. Most commonly, FMD is due to medial fibroplasia. Each of intimal fibroplasia, which is common in the pediatric population, and adventitial fibroplasia accounts for approximately only 10% of FMD cases. Medial fibroplasia is characterized by a "string of beads" appearance on CT scan. In the case of renal artery FMD, fibroplasia is typically in the mid to distal portion of the artery. In contrast, atherosclerosis usually occupies the proximal to mid portion of the renal artery in older patients, which makes the differentiation between the two not very difficult. The diagnosis of FMD is based on duplex imaging that shows elevated blood flow velocities in the distal fibroplastic region. DIstinguishing FMD from vasculitis is important, because the latter should always be in the differential diagnosis of FMD. By definition, however, FMD is not an inflammatory disease; elevation in acute phase reactants is not typically seen. Educational Objective: Fibromuscular dysplasia (FMD) is a non-atherosclerotic non-inflammatory vascular disease that is caused by fibroplasia of the arterial layers. It commonly affects the renal and subclavian arteries arteries. Renal artery FMD may be an incidental finding but may present with symptoms of hypertension due to alteration of renal artery hemodynamics. On CT scan, the mid to distal portion of the renal artery shows "string of beads" appearance. References: Image: Plouin PF, Perdu J, La batide-alanore A, Boutouyrie P, Gimenez-roqueplo AP, Jeunemaitre X. Fibromuscular dysplasia. Orphanet J Rare Dis. 2007;2:28. Slovut DP, Olin JW. Fibromuscular dysplasia. N Eng J Med. 2004;350:1862-1871.]]
Approved	Approved::Yes
Keyword	WBRKeyword::Fibromuscular, WBRKeyword::Dysplasia, WBRKeyword::Fibromuscular dysplasia, WBRKeyword::FMD, WBRKeyword::Renal, WBRKeyword::Artery, WBRKeyword::Stenosis, WBRKeyword::Renal artery stenosis, WBRKeyword::Hypertension, WBRKeyword::Vascular, WBRKeyword::String of beads, WBRKeyword::CT, WBRKeyword::scan, WBRKeyword::Computed tomography, WBRKeyword::Pheochromocytoma, WBRKeyword::Takayasu arteritis, WBRKeyword::Aneurysm, WBRKeyword::Blood pressure
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