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NBME 20 Answers

nbme20/Block 1/Question#49

A 56-year-old man comes to the physician because of ...

Fibromuscular hyperplasia of arterioles

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submitted by hayayah(603),

Case of arteriolosclerosis.

Hyperplastic arteriolosclerosis involves thickening of vessel wall by hyperplasia of smooth muscle ('onion-skin appearance')

  • Consequence of malignant hypertension (>180/120 w/ acute end-organ damage)
  • Results in reduced vessel caliber with end-organ ischemia
  • May lead to fibrinoid necrosis of the vessel wall with hemorrhage; classically causes acute renal failure (ARF) with a characteristic 'flea-bitten' appearance
masonkingcobra  From Robbin's: Fibromuscular dysplasia is a focal irregular thickening of the walls of medium-sized and large muscular arteries due to a combination of medial and intimal hyperplasia and fibrosis. It can manifest at any age but occurs most frequently in young women. The focal wall thickening results in luminal stenosis or can be associated with abnormal vessel spasm that reduces vascular flow; in the renal arteries, it can lead to renovascular hypertension. Between the focal segments of thickened wall, the artery often also exhibits medial attenuation; vascular outpouchings can develop in these portions of the vessel and sometimes rupture. +  
asapdoc  I thought this was a weirdly worded answer. I immediately ( stupidly) crossed of fibromuscular dysplasia since it wasnt a younger women =/ +7  
uslme123  I was thinking malignant nephrosclerosis ... but I guess you'd get hyperplastic arteries first -_- +  
hello  The answer choice is fibromuscular HYPERplasia - I think this is different from fibromuscular DYSplasia (seen in young women); +13  
yotsubato  hello is right. Fibromuscular hyperplasia is thickening of the muscular layer of the arteriole in response to chronic hypertension (as the question stem implies) +4  
smc213  Fibromuscular Hyperplasia vs Dysplasia...... are supposedly the SAME thing with multiple names. Fibromuscular dysplasia, also known as fibromuscular hyperplasia, medial hyperplasia, or arterial dysplasia, is a relatively uncommon multifocal arterial disease of unknown cause, characterized by nonatherosclerotic abnormalities involving the smooth muscle, fibrous and elastic tissue, of small- to medium-sized arterial walls. http://www.medlink.com/article/fibromuscular_dysplasia +1  
smc213  *sorry I had to post this because it was confusing!!!*Fibromuscular dysplasia is most common in women between the ages of 40 of and 60, but the condition can also occur in children and the elderly. The majority (more than 90%) of patients with FMD are women. However, men can also have FMD, and those who do have a higher risk of complications such as aneurysms (bulging) or dissections (tears) in the arteries. https://my.clevelandclinic.org/health/diseases/17001-fibromuscular-dysplasia-fmd +1  
momina_amjad  These questions are driving me crazy- fibromuscular dysplasia/hyperplasia is the same thing, and it is NOT this presentation and it doesn't refer to arteriolosclerosis seen in malignant HTN! Is the HTN a cause, or a consequence? I read it as being the cause (uncontrolled HTN for many years) If it was the consequence, the presentation is still not classical! -_- +1  
charcot_bouchard  Poor controlled HTN is the cause here +  
charcot_bouchard  Also guys if u take it as Fibromuscular dysplasia resulting in RAS none of the answer choice matches +  

It is worth clarifying that all the comments are wayyyy off, since Hyperplastic Arteriolosclerosis has nothing to do with Fibromuscular Dysplasia. Note that arteri-ol-osclerosis is exclusively referring to pathology of Arterioles. There are 2 subtypes of arteriolosclerosis, Hyperplastic Arteriolosclerosis is often due to Hypertensive Emergency (as seen in this patient). The other subtype is Hyaline Arteriolosclerosis, often associated with Diabetes Mellitus.

The correct answer choice says "Fibromuscular hyperplasia of arterioles" which is simply a description of what occurs in Hyperplastic Arteriolosclerosis (onion-skinning due to smooth muscle hyperplasia)

+16/- msyrett(17),

severe hypertension leads to hyperplastic arteriolosclerosis leading to arteriolonephrosclerosis (FA'18 --pg 297)

Fibromuscular hyperplasia will cause pre renal azotemia. S. BUN/Cr is >20 in pre renal azotemia but in the question its value is indicative of intrinsic renal failure. very confusing!!

charcot_bouchard  Not really, Hypotension cause pre renal azotemia. Here long standing HTN resulting in end organ damage so intrinsic renal failure +2  
cry2mucheveryday  ugh! i just noticed there's a fairly long h/o of poorly controlled HTN which makes this question simpler now. Thanks!! +