Efficacy and Safety of Tamibarotene(AM80H) for HTLV-1 Associated Myelopathy/ Tropical Spastic Paraparesis (HAM/TSP)

Inclusion Criteria: * Patients who have been diagnosed as HAM according to the WHO criteria * Patients who are positive for HTLV-I antibody in the spinal fluid * Patients, if female, who are not pregnant or breastfeeding, either agreed to take contraceptive measures during and two years after the treatment, or sterile * Patients, if male, who agreed to take contraceptive measures during and six months after the treatment * Patients who have been informed and understood the contents of the study and consented to participate in the signed form. Exclusion Criteria: * Patients who has a rapid progress in the symptoms defined as an increase of two or more in Osame's Motor Disability Score for HAM patients in the past one year. * Patients of hyperlipidemia (serum triglyceride higher than 400 mg/dL) * Patients who were administered new or increased dose of corticosteroid in the past 8 weeks before the intervention * Patients who received steroid pulse therapy in the past 8 weeks before the intervention * Patients who were administered new or increased dose of immunosuppressant in the past 8 weeks before the intervention * Patients with a history of serious drug allergy * Patients with significant complication such as malignancy, severe heart failure, and other serious diseases. * Patients who were in the past administered etretinate.