PEG-glucocerbrosidase is a drug designed to clear out the accumulation of lipid (glucocerebroside) from the blood stream. The drug is actually an enzyme attached to large molecules called polyethylene glycol (PEG). The large molecules of PEG allow the enzyme to remain in the blood stream for long periods of time. By modifying glucocerebrosidase with PEG, it is believed that smaller doses will be required, meaning a reduction in cost for the patient and more convenient administration of the drug. The purpose of this study is to evaluate the effects and safety of enzyme replacement therapy using PEG- glucocerebrosidase for the treatment of Gaucher disease.