〈Editor’s note〉 Restless legs syndrome is a surprisingly common condition, yet it is frequently misdiagnosed as muscle soreness, leg numbness, varicose veins, or peripheral neuropathy. Consequently, many patients miss the optimal window for early intervention and battle chronic fatigue and sleep disruption for years. Heo Kyung, a leading South Korean authority on epilepsy and sleep medicine and director of the Sleep Medicine Center at Dongrae Bongsaeng Hospital, offers a detailed look at recognizing and managing the disorder.
A 58-year-old female patient who recently visited Dr. Heo’s outpatient clinic described a textbook presentation. For roughly five years, she experienced uncomfortable sensations below her knees four to five days a month whenever she lay down to sleep. Over the past year, however, the unpleasant sensations intensified and began occurring almost every night. Moving her legs or walking provided temporary relief, but falling asleep became so difficult that she ultimately sought specialist care.
Her condition is a classic case of restless legs syndrome (RLS), a neurological sleep disorder affecting more than 5% of the population.
Recognizing Key Symptoms and Misdiagnosis Pitfalls
In mild cases, RLS symptoms appear intermittently and may vanish for long stretches, leading many individuals to forgo medical evaluation. When symptoms progress to moderate or severe levels, however, they tend to become chronic. RLS can develop at any age, but its incidence rises steadily up to age 65. Between 40% and 60% of patients have a family history of the disorder, which often correlates with an earlier onset. Women are roughly twice as likely as men to develop RLS.
Because discomfort concentrates in the lower limbs, patients and clinicians routinely mistake RLS for muscle cramps, leg swelling, varicose veins, herniated lumbar discs, arthritis, or peripheral neuropathy. While clinical testing helps rule out these competing conditions, there is no single diagnostic blood test or imaging scan that definitively confirms RLS. Diagnosis relies almost entirely on a detailed medical history and patient-reported symptoms.
The hallmark diagnostic feature of RLS is an irresistible urge to move the legs, usually accompanied by—or driven by—uncomfortable, distressing sensations deep within the limbs. Key clinical criteria include:
Inactivity trigger: Symptoms begin or worsen during periods of rest or inactivity, such as sitting or lying down.
Movement relief: Physical activity like walking, shaking the legs, or stretching provides partial or complete relief for as long as the movement continues.
Evening worsening: Symptoms occur predominantly or exclusively in the evening or at night.
Associated movement: Periodic limb movements—involuntary leg jerks during sleep—frequently coexist with the condition.
Early in the disease course, symptoms manifest only at night. As RLS progresses, discomfort can spill over into daytime rest, particularly during prolonged confinement in automobiles, buses, trains, or airplanes.
Brain Iron Deficiency and Dopamine System Disruptions
While conditions associated with systemic iron deficiency—such as chronic kidney disease or pregnancy—can trigger RLS, most patients present with normal iron levels on standard blood panels. Medical researchers believe the primary underlying mechanism involves central nervous system (CNS) iron deficiency rather than systemic serum iron deficits.
Iron plays a crucial role in dopamine synthesis and receptor function within the brain. CNS iron insufficiency and dopamine signaling abnormalities are closely intertwined. Although symptoms improve significantly with dopaminergic medications, studies also reveal a reduction in dopamine D2 receptor expression. During daylight hours, dopamine activity remains sufficiently balanced. However, as natural circadian rhythms cause dopamine levels to drop in the evening, a relative dopamine deficit emerges, triggering RLS symptoms.
If left untreated, moderate-to-severe RLS severely degrades overall quality of life. Chronic sleep deprivation leads to daytime exhaustion, impaired concentration, reduced cognitive performance, mood disorders like anxiety and depression, and diminished workplace productivity. Furthermore, the repetitive limb movements and frequent micro-arousals associated with RLS repeatedly spike heart rate and blood pressure overnight, disrupting normal nocturnal blood pressure regulation and potentially elevating long-term cardiovascular risk.
Stepwise Treatment Strategies and Clinical Guidance
Managing RLS begins with evaluating systemic iron stores. Because RLS symptoms can worsen even in the absence of clinical anemia, iron replenishment is a key therapeutic step. In RLS management, ferritin levels that fall within the low end of the "normal" population reference range are still treated as insufficient, prompting iron therapy. However, patients should never self-administer over-the-counter iron supplements without medical supervision, as excess iron accumulation carries toxic risks.
Lifestyle modifications provide essential foundational support. Maintaining a rigid sleep schedule, engaging in moderate daily exercise, and cutting caffeine intake help reduce symptom frequency. Warm baths, leg massages, and light stretching before bed can also ease night-onset discomfort, though vigorous exercise late in the evening should be strictly avoided.
Patients should also audit their medication records with a physician. Common over-the-counter and prescription drugs—including sedating antihistamines, certain antidepressants, and antipsychotics—can significantly exacerbate RLS symptoms.
When symptoms occur frequently or severely disrupt sleep, pharmacological therapy is indicated. Clinicians typically prescribe low-dose dopamine agonists (such as pramipexole or ropinirole) or alpha-2-delta ligands (such as pregabalin or gabapentin), which are also used for neuropathic pain. For severe, treatment-resistant cases, low-dose opioids may be considered under strict specialist oversight to manage dependency risks.
"When night falls and your legs feel uncomfortable or driven to move, it is easy to dismiss the feeling as simple physical fatigue," notes Dr. Heo. "However, leaving restless legs syndrome unaddressed deprives the body of restorative sleep and harms long-term health."
Heo Kyung, M.D., Ph.D., earned his undergraduate and master's degrees from Yonsei University College of Medicine and his doctorate from Kyung Hee University Graduate School. Following clinical training in epileptology at Yale New Haven Hospital, he served as a professor of neurology at Severance Hospital, head of the Epilepsy Research Institute at Yonsei University College of Medicine, and director of the Sleep Health Center at Dongrae Bongsaeng Hospital. He has served as chair of the Korean Epilepsy Society and president of the Korean Society of Sleep Research.
