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

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

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.

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).

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.

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.

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.