Post-marketing Study of Gabapentin Enacarbil to Evaluate the Effect in Restless Leg Syndrome (RLS) Patients With Moderate Renal Impairment

Inclusion Criteria: * Patients who have been diagnosed with restless legs syndrome (RLS) according to the international RLS Study Group Diagnostic Criteria * Patients whose score is 15 or greater on the International RLS (IRLS) Rating Scale on the first day of the pre-observation period. * Patients whose creatinine clearance level at the first day of pre-observation period is ≥30 mL/min to \<60mL/min estimated by Cockcroft-Gaul t equation * Patients who provide written consent Exclusion Criteria: * Patients with sleep disorder such as sleep apnea syndrome, which affects the RLS evaluation * Patients with history of augmentation and treatment rebound of RLS symptoms when using dopamine agonis * Patients with neuropathy and movement disorder (diabetic neuropathy, Parkinson's disease, multiple sclerosis, dyskinesia, rheumatoid arthritis etc) * Patients with uncontrolled diabetes \[HbA1c\>7.5% (NGSP value), in the past six months\], iron deficiency anemia, or drug administration of hypnotic sedatives. * Patients who attempted suicide within six months prior to the consent obtained, or who have been diagnosed as a suicide risk by investigator or sub-investigator * Patients with moderate or severe depression * Patients with alcohol dependence or drug intoxication or who have a history of abuse or drug dependence in the past one year * Patients whose job is shift work, professional driver, or engaging in hazardous activities such as operating machinery * Patients with history of hypersensitivity to gabapentin * Patients who have experience to participate in other post-marketing clinical studies or clinical trials within 12 weeks prior to the start of pre-observation * Others: patients who are concluded to be ineligible by an investigator or sub-investigator as ineligible