What is the management and treatment approach for a patient with fibromuscular dysplasia (FMD) presenting with severe ankle pain at rest, prominent vessels, and slight tremor?

Management of Fibromuscular Dysplasia with Severe Ankle Pain at Rest

The severe ankle pain at rest with prominent vessels and tremor is not a typical manifestation of fibromuscular dysplasia and requires urgent evaluation for peripheral arterial disease, critical limb ischemia, or an alternative vascular or neurological etiology, as FMD predominantly affects renal, carotid, and vertebral arteries rather than lower extremity vessels. 1, 2

Understanding the Clinical Disconnect

FMD is a nonatherosclerotic, noninflammatory arterial disease that most commonly involves the renal arteries (causing hypertension) and carotid/vertebral arteries (causing stroke, TIA, or dissection). 2, 3 While FMD can theoretically affect any artery in the body, lower extremity involvement causing severe rest pain is exceptionally rare. 3, 4

Key Clinical Features of FMD (What This Patient Should Have):

• Renal artery involvement: Hypertension in young to middle-aged women, particularly if difficult to control 2, 5
• Carotid/vertebral involvement: Stroke, TIA, Horner syndrome, cranial nerve palsies, or cervical bruit 2
• Upper extremity involvement (rare): Hand/arm claudication or digital ischemia, most commonly affecting the brachial artery 6

What This Patient Actually Has:

• Severe ankle pain at rest: This suggests critical limb ischemia or severe peripheral arterial disease, which is NOT characteristic of FMD 7
• Prominent vessels: Could indicate venous insufficiency, arteriovenous malformation, or compensatory collateral circulation 7
• Slight tremor: Suggests a neurological component unrelated to typical FMD manifestations 2

Immediate Diagnostic Approach

Assess for critical limb ischemia first, as rest pain in the ankle is a red flag for severe arterial insufficiency requiring urgent intervention. 7

Vascular Assessment:

• Palpate pedal pulses (dorsalis pedis and posterior tibial) - absence suggests significant peripheral arterial disease 7
• Measure ankle-brachial index (ABI) using sphygmomanometers and handheld Doppler:
  • ABI <0.40 indicates severe arterial obstruction requiring urgent vascular surgery consultation 7
  • ABI 0.40-0.59 indicates moderate obstruction 7
  • ABI >1.30 suggests poorly compressible vessels from arterial calcification 7
• Examine for venous insufficiency: Edema, skin changes, varicosities that could explain prominent vessels 7

Neurological Assessment:

• Evaluate the tremor: Determine if it's a resting tremor, action tremor, or related to pain/anxiety - this is unrelated to FMD and requires separate neurological evaluation 2

If FMD is Confirmed in This Patient

Should imaging reveal FMD in any vascular bed, the following management applies:

Medical Management (All FMD Patients):

• Initiate antiplatelet therapy to prevent thromboembolism, though optimal drug and dosing remain undefined 7, 1, 5
• Control blood pressure with RAS blockers (ACE inhibitors or ARBs) as first-line agents when percutaneous intervention is not feasible, with careful monitoring of renal function 1, 5
• Annual noninvasive imaging of affected arteries initially to detect progression, reducing frequency once stability is confirmed over 2-3 years 7, 1, 2

Imaging Strategy:

• Begin with duplex ultrasonography as the initial screening test 1, 5
• Proceed to CT angiography or MR angiography from head to pelvis to identify the systemic nature of FMD 2, 5
• Reserve catheter angiography for cases where noninvasive tests are inconclusive or when revascularization is planned during the same procedure 1, 2

Indications for Revascularization:

• Refractory hypertension despite optimal medical therapy 1, 5
• Progressive renal dysfunction with bilateral renal artery stenosis or stenosis to a solitary kidney 7, 1
• Symptomatic cerebrovascular disease: Retinal or hemispheric ischemic symptoms related to carotid FMD 7, 1

Revascularization Techniques:

• For renal FMD: Percutaneous transluminal renal angioplasty (PTRA) without stenting is first-line; reserve stenting only for dissection or angioplasty failure 1, 5, 8
• For carotid FMD: Angioplasty with or without stenting for symptomatic disease only 7, 1

Critical Contraindication:

• Never revascularize asymptomatic FMD regardless of stenosis severity - this is a Class III (No Benefit) recommendation that exposes patients to unnecessary procedural risk 7, 1, 5

Alternative Diagnoses to Consider

Given the atypical presentation, strongly consider:

• Atherosclerotic peripheral arterial disease: More common cause of lower extremity rest pain, especially with risk factors like diabetes, smoking, or cardiovascular disease 7
• Acute arterial thrombosis or embolism: Requires urgent vascular surgery evaluation 7
• Venous insufficiency: Could explain prominent vessels and pain, though rest pain is less typical 7
• Complex regional pain syndrome or neuropathy: Could explain pain and tremor 7

Common Pitfalls to Avoid

• Do not assume lower extremity symptoms are from FMD - this is an extremely rare manifestation and other etiologies are far more likely 6, 3
• Do not delay vascular surgery consultation if ABI <0.40 or clinical signs suggest critical limb ischemia 7
• Do not use stents as first-line therapy for renal FMD if revascularization is needed 1, 5
• Do not treat asymptomatic FMD with revascularization procedures 7, 1