Task: Question Answering
Input (English): Context: Clinical features variability between familial and sporadic restless legs syndrome/Willis-Ekbom disease (RLS/WED) has been previously reported. With this retrospective cohort study, we aimed to determine the clinical and polysomnographic characteristics of 400 RLS/WED patients. Patients with familial RLS/WED were significantly younger than sporadic RLS/WED, while clinical and polysomnographic characteristics were similar in both groups. No difference was found for the age-at-onset between idiopathic and secondary RLS/WED. Periodic limb movements (PLM) index and REM sleep time were higher in idiopathic RLS/WED. Time of onset of symptoms was in the evening or at bedtime in 28.04 and 37.80% of patients, respectively, while in 21.34% of patients onset was more than 1 h after sleep onset. Impulse control and compulsive behaviours (ICBs) were found in 13.29% patients on dopamine agonist therapy. Our analyses support the hypothesis that patients with a familial history of RLS/WED may have a genetic component. Nevertheless, the dichotomy between early and late onset disease seems to be less sharp than previously reported. A large proportion of RLS/WED patients can have atypical features, therefore making the diagnosis challenging. Some cases can be missed even when the patient refers to a sleep specialist, as revealed by the partial absence of daytime symptoms, the high comorbidity with insomnia and other sleep complaints and the high percentage of symptoms beginning after sleep onset. This draws attention on the importance of a careful evaluation of the patient, to recognize potentially treatable secondary forms of RLS/WED. 
 Question: Willis-Ekbom disease is also known as?
Output (English): restless legs syndrome