Background Tacrolimus was used off-label in the treat-ment of Henoch-Schönlein purpura nephritis (HSPN) in children. The objective of this pilot study was to assess its efficacy and safety.

Methods Children with HSPN receiving tacrolimus and steroids as empirical treatment was included. Urine protein was assessed every 2 weeks during treatment. Pharmacogenetic analysis was performed on the CYP3A5 gene.

Results A total of 25 patients with a mean age of 7.2 (range 3–12) years was included in this study. Pro-teinuria returned to negative in 21 patients with a mean treatment duration of 101 (SD 75) days. Patients with CYP3A5*1/*3 had longer duration of treatment achiev-ing negative proteinuria as compared with patients with CYP3A5*3/*3 (131±97 versus 80±39 days). No patients discontinued the tacrolimus treatment due to adverse events, and no drug-related adverse events were shown to have a causal association with tacrolimus therapy.

Conclusion This preliminary study shows that tacrolim-us might be an effective, and well-tolerated drug for the treatment of HSPN in children.