A randomized controlled trial of oral phosphate binders in the treatment of pseudoxanthoma elasticum.

Background: Pseudoxanthoma elasticum (PXE) is a rare connective tissue disorder involving fragmentation and mineralization of elastic fibers predominantly in the skin, eyes, and cardiovascular system.

Objective: The objective of this study was to assess the efficacy of sevelamer hydrochloride on the reversal of elastic fiber calcification and clinical lesions of PXE.

Methods: This was a randomized, double-blind, placebo-controlled, two-part prospective study. In the first year, 40 patients with PXE were randomized to receive either sevelamer hydrochloride (800 mg by mouth three times daily) or placebo in a 1:1 ratio. In the second year, all patients received sevelamer hydrochloride (800 mg by mouth three times daily).

Results: In the first year, the placebo and treatment groups' mean calcium scores decreased from 29.52 to 15.97 (41.93% mean improvement) and 27.48 to 16.75 (38.37% mean improvement), respectively. In the second year, the mean calcium scores decreased to 13.36 (53.94%) and 14.03 (51.35%) in these groups. The mean clinical score in the placebo group decreased from 6.25 to 6.05 at year 1 (2% improvement) whereas the mean clinical score in the sevelamer hydrochloride group decreased from 7.10 to 6.55 (7% improvement). In year 2, the scores in the original placebo and sevelamer hydrochloride groups decreased to 5.33 (14% improvement) and 5.72 (19% improvement), respectively.

Limitations: Magnesium stearate in our placebo and active drugs may have played a confounding role in this study, contributing to the small differences observed in these two groups.

Conclusion: Sevelamer hydrochloride produced a reduction in both calcification levels and clinical scores; however, this difference was not statistically significant compared with placebo. Future clinical studies should examine the inhibitory role and potential therapeutic effect of magnesium in PXE.