Objective: We sought to examine factors that predisposed 1.5% (10/672) of renal transplant recipients treated with a cyclosporine (CsA)/sirolimus (SRL)/steroid immunosuppressive regimen to develop hemolytic uremic syndrome (HUS).
Methods: Two cohorts of recipients were treated for 1-212 months (mean: 25.0+/-26.4, median: 18.1) with concentration-control CsA regimens based upon either area under the concentration-time curve (AUC; n=412 patients) or trough measurements (C0; n=260 patients).
Results: The only demographic feature more common to affected patients was an original glomerulopathic disease in 7 patients, 4 of whom had displayed IgA glomerulonephritis. All 10 affected patients showed a clinical picture of hemolysis with schistocytes, thrombocytopenia (nadir: 35,000+/-19,600 platelets/mm3), as well as elevated serum levels of lactate dehydrogenase (1697+/-1427 IU) and creatinine (Scr; 2.05+/-1.52 mg/dL prediagnosis to 5.13+/-2.43 mg/dL at diagnosis). Seven patients experienced adverse events concomitant with the bout of HUS, namely, acute rejection episodes prior to (n=2) or during (n=3), and 2 patients, infections (Herpes simplex and pancolitis). The mean values of daily steroid dose and the immunosuppressive drug C0 values were above the putative therapeutic targets: namely, CsA C0=294.9+/-153.2 ng/ml versus 150+/-50 ng/ml and SRL C0=20.1+/-14.0 ng/ml versus 10+/-5 ng/ml, respectively. The therapeutic approach included discontinuation of CsA in 9/10, which was transient in 6/9; discontinuation of SRL in all 10, which was transient in 3, OKT3 for concurrent rejection in 3, and plasmapheresis in 5 patients. At 24 weeks postdiagnosis 9/10 patients have well-functioning kidneys with a mean Scr value of 1.6+/-0.59 mg/dL. One patient who underwent transplant nephrectomy subsequently succumbed due to a cluster of refractory thrombocytopenia, Aspergillus infection, and multiorgan failure.
Conclusion: This initial experience suggests that a time-limited and reversible de novo HUS syndrome may be less frequent and milder among renal transplant recipients treated with SRL-based immunosuppression.