B-cell dysfunction and depletion using mycophenolate mofetil in a pediatric combined liver and kidney graft recipient

The use of mycophenolate mofetil (MMF) in combination with cyclosporin A (C sA) and steroids is well established after kidney transplantation (Tx) in c hildren. A 9-yr-old girl with primary hyperoxaluria type 1 and systemic oxa losis underwent a combined kidney and liver Tx at our institution. The post -operative immunosuppression consisted of CsA, prednisolone, and MMF, Four weeks post-transplant the girl suffered from a severe urinary tract infecti on caused by Pseudomonas aeruginosa, when the serum immunoglobulin G (IgG) concentration was found to be critically low (<1.53 g/L). Additionally, the re was an isolated B-cell depletion (240/ muL) at that time. In the followi ng course, the B-cell count was significantly diminished until the MMF was stopped 13 weeks posttransplant. As a result of the very low serum IgG conc entration, intravenous immunoglobulin (IVIG) substitution was necessary. Th ere was no significant loss of immunoglobulins in the ascites and urine and no other medication with possible side-effects on B cells was given. We su ggest that MMF can lead to suppressed IgG production by B cells and can cau se a defective differentiation into mature B cells. In vitro studies demons trated these effects of MMF on B cells, but no in vivo cases of this phenom enon have been reported. B-cell counts and serum IgG concentrations returne d to normal values after discontinuing the MMF, As we can assume that the o bserved B-cell dysfunction and depletion were MMF related, we suggest that serum Ige concentrations should be monitored when MMF is used after solid-o rgan Tx.