Early detection of renal damage caused by fumaric acid ester therapy by determination of urinary β2-microglobulin.

Abstract

Fumaric acid esters are considered efficacious and safe drugs for the treatment of psoriasis. Renal damage, caused either by acute renal injury or Fanconi syndrome, is a recognized side-effect of this therapy. To investigate whether the measurement of urinary excretion of β2-microglobulin, a marker of renal proximal tubular dysfunction, allows early detection of kidney damage before an increase in serum creatinine or significant proteinuria occurs. Urinary β2-microglobulin excretion was measured regularly in 23 patients undergoing fumaric acid ester therapy. Urinary β2-microglobulin remained normal in all 10 male patients. Three (23%) out of 13 female patients experienced an increase in urinary β2-microglobulin excretion. In two of these patients a sharp increase was observed in association with high doses. One further patient had moderately elevated levels on rather low doses of fumaric acid esters. After discontinuing treatment, urinary β2-microglobulin levels returned to normal within a few weeks. Determination of urinary β2-microglobulin possibly allows early detection of renal damage by fumaric acid esters. Female patients seem to be prone to this side-effect, especially when taking high doses.