Early-onset and late-onset forms of restless legs syndrome have been described. The early-onset form begins before age 45, and sometimes as early as childhood; the and symptoms of this form usually worsen slowly with time. The late-onset form begins after age 45; its symptoms tend to worsen more rapidly. [from Genetics Home Reference; restless legs syndrome; 2017.02.16]

Restless legs syndrome (RLS) is a neurologic disorder characterized by an uncontrollable urge to move the legs during periods of rest. The majority of patients with RLS also have periodic limb movements in sleep, which are characterized by involuntary, highly stereotypical, regularly occurring limb movements (Stefansson et al., 2007; pubmed:17634447). The disorder can result in nocturnal insomnia and chronic sleep deprivation (Bonati et al., 2003; pubmed:12764067). [from MIM:611185, MIM:102300; 2017.01.10]

Iron is involved in several critical activities in brain cells, including the production of dopamine, which is involved in the control of physical movement; it is postulated that malfunction of the dopamine signaling system may underlie the abnormal movements observed with restless legs syndrome. [from Genetics Home Reference; restless legs syndrome; 2017.02.16]

Lower levels of ferritin and higher levels of transferrin in the cerebrospinal fluid (but not in blood serum) have been observed in RLS patients (Earley et al., 2000; pubmed:10762522 and others). [from MIM:102300; 2017.01.10]