Proteinuria is the predominant risk factor for renal disease progression in Fabry disease (FD). When urine protein excretion is controlled to <0.50 g/24 h, the rate loss of glomerular filtration rate (GFR) is not significantly different from 0. However, enzyme replacement therapy (ERT) alone does not appear to decrease proteinuria and it has been recommended that patients receiving ERT also receive angiotensin converting enzyme inhibitors or angiotensin receptor blockers (ACEi/ARBs). Emerging evidences show that paricalcitol (PCT) reduces proteinuria in presence of intensified inhibition of Renin-Angiotensin-System (RAS). However, there is no evidence in FD. We evaluated the antiproteinuric effect of PCT in FD patients with proteinuria >0.50 g/24 h persisting despite the ERT and anti-RAS therapy titrated to maximum tolerated dosage.
49 patients with FD were considered for recruitment. The inclusion criteria were: written informed consent, age >18 years and proteinuria >0.50 g/24 h despite the use of ERT and ACEi/ARBs. Fourteen patients were selected and studied in the first six months of add-on oral PCT (1 mcg/day) and, in order to verify the dependence of proteinuria reduction on PCT, three months after drug withdrawal.
At baseline, 7 patients were male and 7 female, age 48 ± 14 yrs, systolic/diastolic blood pressure (BP) 124 ± 8/73 ± 8 mmHg, GFR 78.3 ± 26.3 mL/min/1.73 m2 and proteinuria 1.3 ± 0.57 g/24 h. Six months of add-on PCT significantly decreased proteinuria to 0.41 ± 0.39 g/24 h, with levels less than 0.50 g/24 h achieved in 4 patients at month 1, 5 at month 3, and in 12 by month 6, in absence of changes of BP and GFR. Proteinuria recovered to basal value after drug withdrawal.
In conclusion, our study is the first evidence that Paricalcitol is effective in reducing proteinuria in FD patients in presence of ERT and anti-RAS therapy.