 In terms of standard of care, the subject will have two clinical visits charged to the subject andor the subjects insurance company, one at the initiation of the study drug baseline and one at the study completion 52 weeks. Study drug will be attempted to be initiated during the off week, approximately one week following a dose of ERT, and ERT will continue throughout the duration of the study. Thereafter, study visits will be during the off week. The 6, 12, and 18 week visits will be research visits not charged to the subject andor the subjects insurance company in order to determine subjects overall health status and measure early signs of motor improvement. The initial dose of clenbuterol will be 40 mcg per oral each morning for one week, followed by 40 mcg BID for the next 5 weeks until the week 12 visit. If the 40 mcg BID per oral is well tolerated, the dose will be increased to 80 mcg each morning40 mcg each evening for one week, followed by 80 mcg BID for the next 5 weeks until the Week 18 visit. If 80 mcg BID is tolerated at Week 18, the subject will continue on that dose until Week 52. 