A Study of Renal Function in Treatment-naïve, Young Male Patients With Fabry Disease

Patients who meet all eligibility criteria based on screening assessments will be scheduled
to return to the clinic for assessments of renal function and other disease-related
parameters, which may be scheduled over one or more clinical investigation visits. The
clinical investigation visit(s) will be scheduled such that renal and cardiac assessments
occur after the required medication washout (see exclusion criterion); other procedures may
be performed either before or after the medication washout, at the discretion of the
investigator.

Up to 100 patients will be enrolled in the study, including a minimum of 15 patients in each
of the following age groups (based on age at screening): 5 to 11 years, 12 to 17 years, and
18 to 25 years.

All patients will be encouraged to enroll in the Fabry Registry (NCT00196742) for continued
follow-up after completion of the study.

Inclusion Criteria:

- The patient and/or their parent/legal guardian is willing and able to provide signed
informed consent. If the patient is below the age of consent per local guidelines, he
is willing to provide assent, if deemed able to do so.

- The patient must have a confirmed diagnosis of Fabry disease as documented by
leukocyte α-galactosidase A (αGAL) of <4 nmol/hr/mg leukocyte (preferred assay;
results from a central laboratory). If the leukocyte αGAL activity assay is difficult
to obtain, the patient may be enrolled based on documented plasma αGAL <1.5
nmol/hr/mL (results from a central laboratory), with the agreement of the Genzyme
Medical Monitor.

Exclusion Criteria:

- Patient has received prior treatment with enzyme replacement therapy (ERT) or oral
pharmacological chaperone therapy for Fabry disease.

- Patient has received an investigational drug within 30 days of the screening visit.

- Patient is receiving any of the following medications and is clinically unable or
unwilling to temporarily discontinue treatment with these medications for the
indicated washout period prior to the renal function assessments until completion of
these assessments:

- Angiotensin converting enzyme inhibitors or angiotensin receptor blockers (6
week washout);

- Non-steroidal anti-inflammatory drugs (3 day washout).

- NOTE: Patients who are on chronic dialysis or have had a kidney transplant will
not be required to discontinue the above medications because renal function
assessments will not be performed in these patients.

- Patient has any contraindication mentioned in the labeling of iohexol. NOTE: patients
with an eGFR <30 mL/min/1.73m^2 and patients who are on chronic dialysis or have had
a kidney transplant may be enrolled irrespective of any contraindication to iohexol
because iGFR will not be measured in these patients.

- Patient has any medical condition or extenuating circumstance which, in the opinion
of the Investigator, could interfere with the patient's ability to complete all study
procedures, or with the interpretation of study results (e.g., diabetes mellitus).

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