What is the most likely underlying cause of secondary hypertension in a young adult?

Renal Artery Stenosis is the Most Likely Cause

In this 18-year-old man with severe hypertension (172/94 mmHg) and no features suggesting obesity, family history, or other secondary causes on examination, renal artery stenosis—specifically fibromuscular dysplasia—is the most likely underlying etiology among the options provided.

Clinical Reasoning

Why Renal Artery Stenosis is Most Likely

• Renal and renovascular disease are among the most common secondary causes of hypertension in young patients, accounting for 34-79% of secondary hypertension cases in pediatric referral centers 1
• Renovascular disease (including renal artery stenosis) was present in 12-13% of pediatric secondary hypertension cases in retrospective series 1
• In young adults, particularly young women, fibromuscular dysplasia is the predominant cause of renovascular hypertension and presents with early-onset, severe hypertension 2, 3
• This patient's severe, persistent hypertension without obesity or positive family history strongly suggests a secondary cause rather than primary hypertension 1

Why NOT Coarctation of the Aorta

While coarctation is an important consideration in young hypertensive patients, several factors make it less likely here:

• Coarctation is characterized by a specific physical examination finding: right arm BP that is 20 mm Hg or more greater than lower extremity BP 1, 4
• The classic presentation includes delayed or absent femoral pulses and radio-femoral delay 4, 5
• A systolic murmur is typically heard on auscultation 5, yet this patient has "regular heart rate and rhythm without murmur" [@question stem]
• The physical examination described shows no evidence of these pathognomonic findings, making coarctation unlikely despite its importance as a cardiac cause of secondary hypertension [@2@, 1]

Why NOT the Other Options

Pheochromocytoma:

• Typically presents with episodic symptoms, labile hypertension, and pallor [@7@, 3]
• This patient has persistent, not episodic, hypertension and appears "well developed and well nourished" without distress
• Pheochromocytoma is uncommon compared to renal causes [@7@, 3]

Nephrolithiasis:

• Does not cause chronic hypertension
• Would present with acute symptoms (flank pain, hematuria)
• Not a recognized cause of secondary hypertension

Sleep Apnea:

• Prevalence is 25-50% in resistant hypertension [@7@, 3]
• This patient is "well developed and well nourished" without mention of obesity, snoring, or daytime sleepiness
• More common in obese patients [@7@, 3]

Diagnostic Approach for This Patient

Initial Evaluation Should Focus On:

• Renal ultrasound with Duplex Doppler to evaluate for renovascular disease [@7@, 3]
• Basic laboratory screening: serum creatinine, eGFR, urinalysis, and urinary albumin-to-creatinine ratio [@7@, 3]
• Four-extremity blood pressure measurements to definitively exclude coarctation [@10@, 5]
• If renal ultrasound is suggestive, proceed to CT or MR renal angiography for definitive diagnosis [2, @8@]

Key Clinical Pearls

When to suspect secondary hypertension in young patients:

• Age <30 years with severe hypertension (as in this case) [@7@, 3]
• Substantial BP elevation (often >99th percentile) with little family history [@1@, 1]
• Absence of obesity in the setting of severe hypertension [1, @2@, 1]

Common pitfall to avoid:

• The American College of Cardiology warns against performing expensive imaging before completing basic screening and physical examination [@8