Natural History and Structural Functional Relationships in Fabry Renal Disease Treatment Outcomes(Changes)in Fabry Renal Disease Study

1. Much of the natural history of Fabry renal structural changes will occur without detectable renal functional alterations. 2. Structural changes associated with the initial onset of proteinuria and those associated with the subsequent progressive loss of filtration function will differ and will be best described by non-linear models. 3. There will be sufficient precision of Fabry renal structural-functional relationships to support renal structure as an acceptable clinical trial surrogate endpoint for later renal functional deterioration.

The second component examines the effects of age and gender at start of enzyme replacement therapy (ERT), as well as dosage levels of ERT on the renal cellular clearance of GL3 from Fabry patients by comparing baseline to follow-up kidney biopsies performed 5, 11, and 60 months later, with all comparisons matched for ERT treatment duration. Our hypotheses for this component of the study are as follows:

1. Enzyme Replacement Therapy(ERT) instituted at younger ages is more effective in reducing podocytes(PC),distal tubular cells(DTC),and arterial smooth muscle cells (ASMC)GL-3 than in older Fabry patients. 2. Earlier institution of ERT will stabilize PC numbers while later ERT institution, especially in proteinuric adults, may not prevent progressive decline in PC numbers and associated glomerular sclerosis, tubulointerstitial injury, and GFR loss. 3. Whereas lower ERT dose may effectively clear GL-3 from endothelial and mesangial cells, it will be less effective in clearing GL-3 from PC and also from DTC and ASMC. 4. Affected cells will be cleared of GL-3 equivalently in females and males.