Fibromuscular Dysplasia



Fibromuscular Dysplasia


A. Brad Farris, III, MD










Fibromuscular dysplasia occurs in 3 main varieties: A) intimal fibroplasia, B) medial fibromuscular dysplasia, and C) periarterial (adventitial) fibroplasia.






The medial fibroplasia form shows disoriented medial smooth muscle image that protrudes into the lumen of the renal artery (trichrome stain).


TERMINOLOGY


Abbreviations



  • Fibromuscular dysplasia (FMD)


Synonyms



  • Arterial fibrodysplasia


  • Fibromuscular hyperplasia


  • Intimal or periarterial (adventitial) fibroplasia


Definitions



  • Idiopathic, segmental, noninflammatory, nonatherosclerotic small and medium-sized artery diseases causing stenosis and aneurysms


  • 3 major categories



    • Medial


    • Intimal


    • Periarterial (adventitial)


ETIOLOGY/PATHOGENESIS


Genetic



  • Sibling affected in 11% of patients


  • Medial fibroplasia form may be congenital since it appears to be malformation


  • Occasionally, associated Ehlers-Danlos syndrome type IV or Marfan syndrome


  • 1 report of increased prevalence of angiotensin converting enzyme (ACE) I allele


Environment



  • Smoking


Female Gender



  • No link to estrogens or oral contraceptives proved


CLINICAL ISSUES


Epidemiology



  • Incidence



    • Estimated 4/1,000 for symptomatic renal FMD



      • Medial: 60-85%


      • Intimal: 1-5%


      • Periarterial: < 1%


    • 10-20% of patients with renal artery stenosis


  • Age



    • Younger (15-50 years) for fibromuscular dysplasia


    • Older (> 50 years) for fibrotic forms


  • Gender



    • Female predominance (medial form)



      • 85% affect women under 50 years old


    • Male predominance (intimal form)


Site



  • 60-90% involve renal arteries



    • 50% bilateral


    • Distal 2/3 of renal artery


    • Extends into arcuates and interlobular arteries



      • May account for continued hypertension after correction of extrarenal stenosis


    • May have associated aneurysm


  • May involve multiple vascular beds



    • Carotid arteries (26%)


    • Mesenteric/intestinal arteries (9%)


    • Iliac arteries (5%)


    • Popliteal, hepatic, coronary, and subclavian arteries (9%)


    • Less commonly, aorta and brachial, superficial femoral, tibial, and peroneal arteries


Presentation



  • Hypertension


  • Asymptomatic


  • Associated with hypertrophic cardiomyopathy



Laboratory Tests



  • Renin levels elevated


Treatment



  • Surgical approaches



    • Surgical correction curative in ˜ 70%


    • Percutaneous transluminal renal angioplasty (PTRA) is treatment of choice


    • Complex reconstruction, such as aortorenal bypass, is required in difficult cases


  • Drugs



    • Hypertension may respond to ACE inhibitors but not most other antihypertensive agents


Prognosis



  • Good, if corrected


  • If untreated, progressive narrowing may occur over 10 years, as judged by angiography



    • Obstruction, dissecting aneurysms, and emboli may result


    • Sudden death, particularly in FMD of cardiac arteries (e.g., artery supplying the sinus node) may occur


  • Renal failure rare


IMAGE FINDINGS


General Features



  • CT and catheter angiography useful in identifying areas of stenosis or classical “string of beads” appearance


MACROSCOPIC FEATURES


General Features



  • Beaded pattern of aneurysms and stenosis in renal artery branches


Size



  • Kidney may show decreased cortical thickness


MICROSCOPIC PATHOLOGY


Histologic Features

Jul 7, 2016 | Posted by in PATHOLOGY & LABORATORY MEDICINE | Comments Off on Fibromuscular Dysplasia
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