An article from ABC News tells us that researchers may have discovered a cause for restless legs:

Now, scientists may have pinpointed the gene that increases the chances that people will kick in their sleep. Their findings, which could have big implications for many RLS sufferers, are presented in the current issue of the New England Journal of Medicine.

"One of the components of RLS that is found in somewhere around 80 percent of patients was, in addition to having discomfort in the legs, that they move their legs in a dramatic fashion," said Dr. Kári Stefánsson, president of deCODE Genetics, a biotechnology company based in Reykjavik, iceland.

What causes the misery of restless legs syndrome? According to an article on MySleepCentral.com:

CAUSES

What causes restless legs? The cause is unknown, although recent research suggests that a single unknown gene causes many of the cases. It is known that RLS is hereditary, with some families having several members suffering from the disorder. RLS is associated with iron deficiency, disorders of the peripheral nerve (e.g. neuropathy) and various other movement disorders (such as Parkinson's disease). However, the cause of RLS for most patients remains unknown.

This could be a boon and a validation for the much misunderstood restless legs syndrome. Or, as WBIR.COM puts it:

A genetic link can work wonders at validating conditions like PMDD and RLS. It's an endorsement that brings peace of mind for patients,and the potential to revolutionize treatment.

*Graphics from ABC News