Renal dysfunction in patients taking fumaric acid esters - a retrospective cross-sectional study.

Background Fumaric acid esters (FAE) have been used for over 30 years in the management of psoriasis. There have been a number of case reports linking the use of FAE with nephrotoxicity, including acute renal injury and Fanconi syndrome. However, one large multicentre retrospective trial showed no evidence of renal dysfunction with FAE. Objectives/aims The aim of this study was to determine the number of patients in our institution being treated with FAE who developed significant proteinuria or renal dysfunction. Methods This was a single-centre retrospective study assessing all patients on FAE who attended for follow-up during an 18-week period between February and June 2015. Demographics, comorbidities, duration and dose of treatment with FAE, proteinuria, renal function and other biochemical serum abnormalities were recorded. Results One hundred and twenty-seven patients were included in the study. Eighty-two patients had proteinuria detected at some stage during treatment with FAE, and 18 of these had persistent proteinuria (positive in at least three consecutive specimens, 12 weeks apart). Six patients (five female) developed proximal tubular dysfunction (PTD). The risk factors for the development of PTD appear to be lower bodyweight (P = 0.03), higher dose per weight (P = 0.03) and longer duration of treatment (P = 0.03). Renal dysfunction improved on discontinuation or dose reduction in FAE. Conclusion Fumaric acid esters are frequently associated with transient or persistent proteinuria. Significant renal dysfunction is rare and usually reversible on dose reduction or discontinuation of FAE. This study highlights the importance of screening for proteinuria. Higher doses per weight of treatment and longer duration of FAE therapy are likely risk factors for PTD.