Pharmacokinetics and Tolerability of Zavesca® (Miglustat) In Patients With Juvenile GM2 Gangliosidosis

Inclusion Criteria: * Diagnosis of GM2 gangliosidosis confirmed by demonstration of profound deficiency of β-hexosaminidase A or A \& B in peripheral blood leukocytes or cultured skin fibroblasts * Aged 6 to 20 years * Onset of characteristic clinical symptoms of the disease before age 15 years * Normal renal or hepatic function Exclusion Criteria: * Fertile patients who do not agree to use adequate contraception throughout the study and for 3 months after cessation of miglustat treatment. * Patients who cannot tolerate the study procedures, cannot be compliant to therapy or who are unable to travel to the study center as required by this protocol. * Patients receiving other investigational agents within 3 months of study initiation. * Patients with disease that may affect absorption or elimination of drugs. * Patients suffering from clinically significant diarrhea (\>3 liquid stools per day for \> 7 days) without definable cause within 3 months of baseline visit, or who have a history of significant gastrointestinal disorders. * Patients with swallowing difficulties. * Patients with a high probability of dying during the study. * Patients who in the opinion of the investigator (for whatever reason) are thought to be unsuitable for the study.