Abstract
Background: Rituximab (RTX) has recently been introducedas a second-line therapy for nephrotic syndrome in children. Studies show that RTX given during the nephrotic state maybe less effective than treatment during a non-nephrotic state, possibly due to loss of RTX in the urine.Case-Diagnosis/Treatment. We describe a 10-year-old boywith steroid-resistant nephrotic syndrome (SRNS) treatedwith RTX during a phase of active non-selective proteinuria. The serum half-life of RTX in this patient was less than 1 day compared to 20 days in patients without protein losses. Urinary clearance was at least 25 %, compared to approximately 0 % in control patients. However, RTX loss in the urine, aswell as in pleural effusion and ascites, only partly explains therapid drop in the serum RTX concentration of this patient.

Conclusions
Serum half-life of RTX can be extremely short,partly due to excessive urinary losses in therapy-resistant nephrotic syndrome with non-selective proteinuria, as seen in our patient. These findings may help to explain the poor results of RTX treatment in patients with active proteinuria.

dx.doi.org/10.1007/s00467-015-3120-8, hdl.handle.net/1765/81409
Pediatric Nephrology
Department of Pediatrics

Counsilman, C.E, Jol–van der Zijde, C.M, Stevens, J, Cransberg, K, Bredius, R.G.M, & Sukhai, R.N. (2015). Pharmacokinetics of rituximab in a pediatric patient with therapy-resistant nephrotic syndrome. Pediatric Nephrology, 30(8), 1367–1370. doi:10.1007/s00467-015-3120-8