Why does a patient with morbid obesity and heart failure experience restless leg syndrome (RLS) symptoms while sitting, but not when laying down at night?

Why RLS Symptoms Occur While Sitting But Not When Lying Down at Night

This patient's symptom pattern does NOT match typical Restless Legs Syndrome, which by definition must worsen in the evening/night and during both sitting AND lying down—the absence of symptoms when lying down at night violates essential diagnostic criterion #4 and suggests an RLS mimic rather than true RLS. 1

Understanding the Core Diagnostic Criteria

The International Restless Legs Syndrome Study Group establishes five essential criteria that ALL must be met for RLS diagnosis 1:

• Criterion #2: Symptoms begin or worsen during periods of rest or inactivity such as both lying down OR sitting 1
• Criterion #4: Symptoms during rest or inactivity only occur or are worse in the evening or night than during the day 1
• When symptoms are very severe, the evening/night worsening may not be noticeable but must have been previously present 1

Your patient experiences symptoms ONLY while sitting and NOT when lying down at night—this directly contradicts the fundamental circadian pattern required for RLS diagnosis. 1

Most Likely Alternative Diagnoses (RLS Mimics)

Given the patient's morbid obesity and heart failure, consider these conditions that commonly masquerade as RLS 1:

Venous Stasis and Leg Edema

• Venous insufficiency worsens with prolonged sitting (dependent position increases venous pooling) but improves when lying down with legs elevated at night 1
• Heart failure exacerbates venous stasis, making this the most probable diagnosis in this patient 1, 2
• The American Geriatrics Society notes that venous varicosities are specifically listed as RLS mimics that meet criteria 1-4 but are NOT RLS 1

Positional Discomfort

• Morbid obesity creates mechanical stress on joints and soft tissues that worsens with sitting (weight compression) but resolves when lying down (weight distribution) 1
• This is explicitly listed as an RLS mimic that must be excluded 1

Arthritis

• Joint pain from osteoarthritis (common with obesity) may worsen with sitting due to joint positioning but improve when lying down in a comfortable position 1

Critical Diagnostic Approach

Ask these specific differentiating questions 1, 3:

• "Do you have an urge to move your legs, or is it just discomfort/pain?" (RLS requires an urge to move) 1
• "When you lie down at night to sleep, do the symptoms return or worsen?" (True RLS worsens at night regardless of position) 1
• "Is the sensation relieved by any movement (walking, stretching), or only by specific position changes?" (RLS improves with any movement; positional discomfort only improves with position change) 1
• "What does it feel like—creepy-crawly/burning/itching, or is it swelling/heaviness/aching?" (RLS has characteristic dysesthesias; venous stasis causes heaviness) 1, 3

Physical Examination Priorities

Perform a focused vascular and musculoskeletal exam 1:

• Check for pitting edema (suggests venous stasis/heart failure) 1
• Assess for venous varicosities and skin changes of chronic venous insufficiency 1, 2
• Evaluate peripheral pulses to exclude arterial insufficiency 3
• Examine joints for signs of arthritis 1
• Perform a thorough neurologic exam looking for peripheral neuropathy or radiculopathy 1

Laboratory Evaluation

If you still suspect RLS after excluding mimics 1:

• Check morning fasting serum ferritin and transferrin saturation (ferritin <50 ng/mL suggests iron deficiency contributing to RLS) 1, 2
• However, given this patient's atypical presentation, do NOT initiate RLS-specific treatment until the diagnosis is confirmed 1

Common Pitfalls to Avoid

• Do not assume all leg discomfort at rest is RLS—the absence of nighttime symptoms when lying down is a red flag that this is NOT RLS 1
• Do not start dopaminergic agents (which are now recommended against anyway) without confirming true RLS, as this exposes the patient to unnecessary risks including augmentation and impulse control disorders 1, 4
• Do not ignore the heart failure and obesity—these conditions directly explain why symptoms would worsen with sitting (venous pooling, mechanical stress) but improve when lying down 1, 2

Management Based on Correct Diagnosis

For venous stasis/edema (most likely):

• Optimize heart failure management 1
• Compression stockings during daytime 1
• Leg elevation when sitting 1
• Diuretic optimization if indicated 1

Only if true RLS is confirmed after excluding mimics:

• Check iron studies and supplement if ferritin ≤75 ng/mL 4
• First-line treatment: gabapentin, gabapentin enacarbil, or pregabalin 4
• Avoid dopamine agonists due to augmentation risk 4