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.

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