How Restless Legs Syndrome Typically Begins
RLS typically starts with an uncomfortable urge to move the legs that worsens during rest or inactivity, improves with movement, and follows a characteristic circadian pattern with symptoms appearing or intensifying in the evening and at night. 1
Initial Symptom Presentation
The onset of RLS is characterized by four cardinal features that must all be present:
- An irresistible urge to move the legs, usually accompanied by uncomfortable and unpleasant sensations in the legs (though sometimes the urge exists without distinct sensations) 1, 2
- Symptoms begin or worsen during periods of rest or inactivity, such as when lying down or sitting 1, 3
- Relief occurs with movement such as walking or stretching, and continues as long as the activity is maintained 1, 4
- A predictable circadian pattern where symptoms only occur or are significantly worse in the evening or night compared to daytime 1, 5
Age and Pattern of Onset
The timing and pattern of RLS onset differs between primary and secondary forms:
- Primary (idiopathic) RLS develops at an earlier age and has a strong genetic basis, with first and second-degree relatives having significantly increased risk 6
- Secondary RLS typically presents later in life, usually in the fifth to seventh decade, without family history 6
- RLS severity generally worsens through the first seven to eight decades of life, though it may actually lessen in old age 2
Frequency and Severity at Onset
Initial symptom frequency varies considerably:
- Symptoms may occur less than once per month or year initially, progressing to more frequent episodes 1
- Chronic-persistent RLS is defined by symptoms occurring at least twice weekly for the past year when untreated 1
- Intermittent RLS involves symptoms occurring less than twice weekly for the past year, with at least 5 lifetime events 1
- Symptoms may remit for various periods of time, making the course unpredictable 1
Common Descriptive Language
Patients use varied semantic phrases to describe their initial symptoms, but all must report an urge to move:
- The description should be in the patient's own words, particularly important for children 1
- While the legs are most commonly affected, sometimes arms or other body parts are involved in addition to the legs 1
- The sensations are described as uncomfortable and unpleasant, though the specific character varies between individuals 2, 3
Critical Diagnostic Pitfall at Onset
A fifth essential criterion must be met: the symptoms cannot be solely accounted for by another medical or behavioral condition 1. Conditions that superficially mimic early RLS include:
- Leg cramps, leg edema, venous stasis, positional discomfort, muscle aches, habitual foot tapping, and occasionally arthritis 1, 7
- Without proper differential diagnosis, 16% of patients who do not have RLS will be misclassified if only the four symptom criteria are assessed 8, 7
Underlying Mechanisms at Disease Onset
The pathophysiology involves multiple systems from the beginning:
- Reduced intracellular iron in the substantia nigra impairing dopamine transport appears critical in most patients 6
- Iron deficiency is a common underlying mechanism in secondary RLS, including iron-deficiency anemia, end-stage renal disease, and pregnancy 6
- Involvement of the spinal cord, peripheral nerves, and central dopamine and narcotic receptors is part of the disease process from onset 6
Bilateral vs. Unilateral Presentation
- RLS typically affects both legs from onset, even if asymmetric in severity 8
- The diagnostic criteria describe affecting "the legs" (plural), indicating bilateral involvement is the standard presentation pattern 8
- Symptoms can be asymmetrical between sides, but this differs from truly unilateral presentation 8