View source for WBR0309

 {{WBRQuestion
|QuestionAuthor= {{YD}} (Reviewed by Serge Korjian)
|ExamType=USMLE Step 1
|MainCategory=Pathology
|SubCategory=Renal
|MainCategory=Pathology
|SubCategory=Renal
|MainCategory=Pathology
|SubCategory=Renal
|MainCategory=Pathology
|MainCategory=Pathology
|MainCategory=Pathology
|SubCategory=Renal
|MainCategory=Pathology
|SubCategory=Renal
|MainCategory=Pathology
|SubCategory=Renal
|MainCategory=Pathology
|SubCategory=Renal
|MainCategory=Pathology
|MainCategory=Pathology
|SubCategory=Renal
|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). Angiography demonstrates small stenoses along the mid to distal left renal artery with areas of small aneurysms that cause a string of beads appearance (shown below).  What is this patient's likely diagnosis?

[[Image:WBR0309.jpg|500px]]
|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 described in the literature. Generally, it accounts for only 1% of cases of arterial stenoses. FMD may be an incidental finding, but patients may present with symptoms of [[hypertension]] due to alteration in [[renal hemodynamics]]. Although FMD may be observed across different age groups and genders, it predominantly affects middle-aged women. FMD has been associated with several conditions, such as smoking, hypertension, and hormonal dysregulation; however, the real cause of FMD is still unclear.

FMD is caused by fibroplasia of any layer of the arterial wall, most commonly [[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 is always part of the differential diagnosis of FMD and requires a very different approach. Typically, FMD is not an inflammatory disease and elevation in [[acute phase reactants]] is not typically observed.
|AnswerA=Takayasu arteritis
|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 characterized by granulomatous inflammation 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. 
|AnswerB=Renal artery stenosis
|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 observed in the proximal to mid portion; in contrast to FMD which mostly occupies the mid to distal regions.
|AnswerC=Fibromuscular dysplasia
|AnswerCExp=Although FMD may be an incidental finding, it may present with hypertension due to alteration in renal hemodynamics.
|AnswerD=Secondary hyperaldosteronism
|AnswerDExp=Although secondary hyperaldosteronism may be a cause of secondary hypertension, the patient's findings are not consistent with secondary hyperaldosteronism.
|AnswerE=Pheochromocytoma
|AnswerEExp=Pheochromocytoma is also a cause of secondary hypertension in young patients.  However, imaging in pheochromocytoma typically demonstrates a mass in the adrenal glands. Renal artery involvement is not likely in pheochromocytoma.
|EducationalObjectives=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 angiography, the mid to distal portion of the renal artery demonstrates a characteristic string of beads appearance.
|References=Plouin PF, Perdu J, La batide-alanore A, Boutouyrie P, Gimenez-roqueplo AP, Jeunemaitre X. Fibromuscular dysplasia. Orphanet J Rare Dis. 2007;2:28. ('''Image''')<br>
Slovut DP, Olin JW. Fibromuscular dysplasia. N Eng J Med. 2004;350:1862-1871.
|RightAnswer=C
|WBRKeyword=Fibromuscular dysplasia, Fibromuscular dysplasia, FMD, Renal artery stenosis,  Hypertension, String of beads appearance, Angiography, Renal angiography, Renal disease
|Approved=Yes
}}