A Study Evaluating Glycosphingolipid Clearance in Patients Treated With Agalsidase Alfa Who Switch to Agalsidase Beta

Inclusion Criteria:

- The patient and/or his parent/legal guardian is willing and able to provide signed
informed consent, and the patient, if <18 years of age, is willing to provide assent
if deemed able to do so.

- Patient is male and has been treated with Replagal® at 0.2 mg/kg every 2 weeks
("q2w") for the 12 months prior to switching to Fabrazyme®.

- The Patient has a confirmed diagnosis of Fabry disease by αGal (α-galactosidase A)
activity and/or genotyping per local standards

- The patient when switched to Fabrazyme® receives the labeled dose, i.e., 0.9 to 1.1
mg/kg ("1 mg/kg") q2w, and must be willing to maintain the labeled dose for the
duration of the study.

Exclusion Criteria:

- The patient is on dialysis or is post renal transplantation

- The patient is in end-stage cardiac failure.

- The patient and/or his parent or legal guardian, in the opinion of the Investigator,
is unable to adhere to the requirements of the study.

- The patient has been switched from Replagal® to Fabrazyme® and does not have
"historical" blood and urine samples