1. Restless Legs Syndrome Slideshow Pictures
2. Take the Restless Leg Syndrome (RLS) Quiz!
3. Weird Body Quirks Slideshow

Medical Author:

Juan Latorre, MD

Medical Editor:

William C. Shiel Jr., MD, FACP, FACR

William C. Shiel Jr., MD, FACP, FACR

Dr. Shiel received a Bachelor of Science degree with honors from the University of Notre Dame. There he was involved in research in radiation biology and received the Huisking Scholarship. After graduating from St. Louis University School of Medicine, he completed his Internal Medicine residency and Rheumatology fellowship at the University of California, Irvine. He is board-certified in Internal Medicine and Rheumatology.

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The cause of restless legs syndrome (RLS) is not known.

• RLS was once thought to be due to disease in the blood vessels of the legs or in the nerves in the legs that control leg movement and sensation. Both of those suggestions have been rejected by further scientific research.
• RLS may be related to abnormalities in brain chemicals (neurotransmitters) that help regulate muscle movements, or to abnormalities in the part of the central nervous system that controls automatic movements. Research is still being done in these areas.

RLS can be primary or secondary. Secondary RLS is caused by an underlying medical condition. Primary (idiopathic) RLS has no known underlying cause. Primary RLS is far more common than secondary RLS.

Many different medical conditions can cause secondary RLS.

• The two most common conditions are iron-deficiency anemia and peripheral neuropathy.
• Iron-deficiency anemia ("low blood") means low levels of hemoglobin, the substance in the blood that carries oxygen and makes the blood appear red.
• Peripheral neuropathy is damage to the nerves of the arms and legs. Peripheral neuropathy has many causes. Diabetes is a common cause of peripheral neuropathy. Peripheral neuropathy causes numbness or lack of sensation, tingling, and pain in the affected areas.
• As many as 40% of pregnant women experience RLS symptoms. The symptoms usually fade within a few weeks after delivery.
• Certain medications or substances can cause RLS. Alcohol, caffeine, anticonvulsant drugs (for example, methsuximide [Celontin], phenytoin [Dilantin]), antidepressant drugs (for example, amitriptyline [Endep, Elavil], paroxetine [Paxil, Paxil CR, Pexeva]), beta-blockers, H2 blockers, lithium (Eskalith, Lithobid), and neuroleptics (antipsychotics) may cause RLS.
• Withdrawal from vasodilator drugs, sedatives, or imipramine (Tofranil, Tofranil-PM) can cause RLS symptoms.
• Cigarette smoking is linked to RLS.
• Other secondary causes include magnesium deficiency, vitamin B-12 deficiency, severe kidney disease (especially if dialysis is required), amyloidosis, Lyme disease, damage to the spinal nerves, rheumatoid arthritis, Sjogren syndrome, and uremia (kidney failure causing build up of toxins within the body).

The causes of primary RLS are unknown, but some of the risk factors are known.

• In 25%-75% of cases, primary RLS seems to run in families. Such hereditary cases of RLS tend to start earlier in life and get worse more slowly than other cases.
• Psychiatric factors, stress, and fatigue can worsen the symptoms of RLS.

Other conditions linked to RLS:

• Parkinson's disease
• Stomach surgery
• Chronic obstructive pulmonary disease (COPD)
• Some tumors
• Chronic venous insufficiency or varicose veins
• Myelopathy or myelitis (damage or inflammation of the spinal cord)
• Hypothyroidism or hyperthyroidism
• Acute intermittent porphyria, a rare metabolic disease leading to accumulation of toxins
• Fibromyalgia
• Peripheral cholesterol microemboli (fragments of cholesterol in the blood vessels)

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