Leonard C. Hymes

Polyomavirus (BK) in pediatric renal transplants: evaluation of viremic patients with and without BK associated nephritis.

Abstract:  Polyoma BK virus (BKV) is emerging as a significant complication in renal transplantation, which may lead to renal dysfunction and graft loss caused by BK nephritis (BKN). We report the management and outcome of 20 children who developed BK viremia. Serum polymerase chain reaction (PCR) for BKV DNA was measured monthly for the first year in transplant recipients and every six months thereafter, or for unexplained creatinine elevation. With seroconversion to +PCR, patients were managed with reduction of immunosuppression. Renal biopsy was performed if PCR or creatinine did not improve. From June 2003 to January 2006, 20 children seroconverted for BKV at 23 to 1410 days post‐transplant (mean 467 days). Sixteen underwent renal biopsy. Eight displayed BKN, three acute rejection and five were normal. Patients with BKN displayed higher PCR and serum creatinine and presented later than children with viremia without BKN. There were no differences between the two groups for age, gender, donor source or immunosuppression. Seven children with BKN received treatment with cidofovir. Thirteen patients (65%) remained PCR+ after reduction of immunosuppression or treatment with cidofovir. Renal function was stable in 16 children (80%) at 13 ± 6 months after seroconversion. Four patients with BKN demonstrated progressive loss of renal function. BKV infection in children can occur as an early complication or may develop years after transplantation. Patients with BKN presented later and displayed higher viral loads and serum creatinine than viremic patients without BKN. Children with BKN remained PCR+ despite reduction of immunosuppression or treatment with cidofovir and were at greater risk for loss of renal function.

Sirolimus in pediatric patients : Results in the first 6 months post-renal transplant

Abstract:  We report our experience with sirolimus in children during the first 6 months after renal transplantation. From July 2000 to January 2004, 66 children received 33 deceased donor and 33 living donor transplants. Maintenance immunosuppression included sirolimus 3 mg/m2 in addition to prednisone and tacrolimus or cyclosporine. Patient survival was 100% and graft survival was 65 of 66. Seven children experienced acute rejection episodes. All were reversible with increased doses of corticosteroid. One case of graft failure was caused by ischemic renal injury. Adverse events included Epstein–Barr viremia (8 patients) with three cases of post‐transplant lymphoproliferative disease (PTLD), cytomegalovirus viremia (4 patients), poor wound healing (4 patients), pneumonitis (3 patients), nephrotic syndrome (3 patients), perinephric abscess (1 patient) and insulin‐dependant diabetes (2 patients). Sirolimus was discontinued in 13 children for adverse events predominantly for wound dehiscence and pneumonitis. Cholesterol levels >200 mg/dL were observed in 33 children. Thrombocytopenia (platelet count <140 000) was not observed. We concluded that early outcomes with sirolimus were acceptable with 98% graft survival and 11% incidence of acute rejection. Medication was discontinued in 20% for adverse events which included poor wound healing and non‐infectious pneumonitis. Infections with cytomegalovirus and Epstein–Barr virus, and PTLD were also significant early complications. Therefore, a sirolimus‐based regimen that is combined with both an interleukin‐2 receptor antibody and a calcineurin inhibitor may be excessive immunosuppression for pediatric renal transplant recipients.

Steroid-resistant, cyclosporine-responsive, relapsing nephrotic syndrome

Eighteen children with steroid-resistant nephrotic syndrome received cyclosporine A (CsA), including 7 patients with minimal change disease, 4 with focal segmental glomerulosclerosis and 7 with mesangial hypercellurarity. Doses were adjusted to maintain whole blood trough levels at 80–200 ng/ml and ranged from 5 to 10 mg/kg (mean 7 mg/kg). Fourteen patients responded after 2 months of therapy with either a complete or partial remission, and received a total of 12 months of CsA with low-dose corticosteroids. Remission rates were similar among the three histological types, although complete remissions occurred more commonly in minimal change disease, while the other two histological types tended to have partial responses. Serum creatinine values ranged from 0.3 to 1.2 mg/dl at the start of treatment and were stable in 17 of 18 patients during CsA therapy. CsA was discontinued after 12 months in 11 responders. Relapses were a significant problem. Nine patients had 16 relapses, all occurring within 6 months after discontinuing CsA; 13 of 16 relapses responded to CsA and corticosteroids. Five children had multiple relapses. Three patients who initially responded to treatment had CsA-resistant relapses. There were no differences among the histological types with respect to the occurrence of relapses or response to CsA after relapsing. Four patients developed chronic renal failure, including 2 of 4 who failed initial therapy and 2 of 3 who developed CsA-resistant relapses. In conclusion, initial therapy with CsA was effective in resolving nephrotic syndrome in steroid-resistant patients. However, CsA dependency, frequent relapses and the development of chronic renal failure presented significant problems.

Predictors of cytomegalovirus disease among pediatric transplant recipients within one year of renal transplantation

Abstract: Cytomegalovirus (CMV) is the most important opportunistic infection in renal transplant recipients and is associated with an increased risk of rejection. Infection can be acquired post‐operatively (from the transplanted organ) or from re‐activation of latent disease. To identify risk factors for CMV disease in a pediatric population within 1 yr of renal transplant, and to generate hypotheses for the pathogenesis of CMV disease in this population, a review of all recipients from 1992 to 1998 in a childrens hospital in Atlanta, Georgia, was undertaken. Medical records of 73 transplants performed on 72 patients were reviewed: nine (12.7%) of 72 individuals, after 73 procedures developed CMV disease. Median time to onset of CMV disease was 52 days post‐transplant (range = 15–95 days). Receipts of mycophenolate mofetil (MMF), demographic factors, and use of cadaveric kidneys were not associated with a significantly elevated risk of CMV disease. Positive donor CMV serostatus was associated with CMV disease (uni‐variate relative risk [RR] = 8.52, Fishers Exact Test [FET] p = 0.010). Patients with transplants in October or November had a higher risk of developing CMV disease (four of 13; 30.8%) than patients transplanted in other months (five of 60, 8.3%); RR = 3.69; p = 0.047, FET). Most transplants of patients who did not develop CMV disease were performed in January through August (48/64; 75.0%); only 25.0% were performed in September through December. In contrast, six of nine (66.7%) transplants in patients who subsequently developed CMV disease were performed in September through December (p = 0.018, FET). Donor CMV‐positive serostatus and transplant in October and November continued to be independently associated with an increased risk of CMV disease when controlled for other factors. The association of transplant in October and November with CMV disease in November–January may be related to an increased risk of seasonal community CMV exposure and primary CMV infection during the peak season for CMV circulation, with subsequent immune suppression promoting progression to disease. Alternatively, co‐infection with seasonal pathogens after exposure from an infected donor during the period of immune suppression may promote progression from CMV infection to CMV disease. Further studies should be undertaken to explore these and other hypotheses, which may have implications for determination of a need for anti‐viral prophylaxis.

Five-year experience using sirolimus-based, calcineurin inhibitor-free immunosuppression in pediatric renal transplantation.

Hymes LC, Warshaw BL. Five‐year experience using sirolimus‐based, calcineurin inhibitor‐free immunosuppression in pediatric renal transplantation.
Pediatr Transplantation 2011: 15: 437–441.

Surveillance renal transplant biopsies and subclinical rejection at three months post-transplant in pediatric recipients

Abstract:  Subclinical acute rejection (SCR) has been increasingly recognized in adult renal transplant recipients with the advent of surveillance biopsies. However, in children, surveillance biopsies are not routinely performed at most centers. Therefore, the incidence, predisposing factors, treatment, and clinical outcomes of SCR remain unclear in children. From August 2004 to December 2005, we performed 36 protocol biopsies at three months post‐transplantation. All patients had received induction therapy with basiliximab and were maintained on prednisone, MMF, and tacrolimus. Sixteen cases of SCR were detected by biopsy (44%). Age, gender, race, donor source, or serum creatinine did not discriminate between children with SCR and those with normal biopsies. All cases of SCR were treated with high doses of methylprednisolone. At one yr post‐transplant, renal function was similar in children with SCR to those with normal surveillance biopsies (p = 0.62). Because of the high incidence of SCR, the maintenance dose of MMF was increased by 50% in 20 children transplanted after December 2005. This resulted in a significant decline in the incidence of SCR from 44 to 15% (p < 0.05). However, the incidence of polyomavirus (BK) viremia also increased significantly in these children (p < 0.005). Conclusion: A high incidence of SCR was found on surveillance biopsies at three months post‐transplant and could not be predicted by age, gender, race, donor source, or serum creatinine. The occurrence of SCR declined significantly by increasing the dose of MMF, but resulted in an increase in BK viremia. We conclude that surveillance biopsies provide valuable information in the management of pediatric renal transplant recipients. Increasing immunosuppression to avoid SCR should be weighed against the risk for infection.

Tacrolimus withdrawal and conversion to sirolimus at three months post-pediatric renal transplantation.

Abstract:  Nephrotoxicity caused by CNI may adversely affect long‐term graft outcomes. For this reason, we have adopted a protocol for withdrawing TAC and converting to SRL at three months post‐renal transplantation. All recipients received basiliximab induction and TAC, MMF, and prednisone. Patients without acute rejection by surveillance biopsy at three months were eligible for SRL conversion. Results: From August 2004 to September 2006, TAC was withdrawn and replaced by SRL in 30 first transplant recipients, who were followed for six to 39 months (mean 18 ± 8). Renal function did not improve significantly after SRL conversion (p = 0.25). Acute rejection occurred in three patients (10%) at five to 12 months after CNI withdrawal. There were no occurrences of wound healing problems, pneumonitis or post‐transplant lymphoproliferative disease. Thrombocytopenia and diabetes each occurred in one patient. Four patients received treatment for hypercholesterolemia. CNI withdrawal and replacement with SRL was an effective regimen in children who did not display biopsy evidence of acute rejection at three months post‐transplant. While these early results are promising, the ultimate benefit of this protocol to enhance the long‐term renal function and graft survival requires ongoing follow‐up.

24 weeks of valganciclovir prophylaxis in children after renal transplantation: a 4-year experience.

Background. Cytomegalovirus (CMV) is the most common opportunistic infection after solid-organ transplant. Valganciclovir prophylaxis significantly reduces disease, but limited data are available on its use in children. Recently, an increase in delayed-onset CMV disease has been noted with some arguing that longer prophylaxis may decrease late-onset disease. Methods. Single-center, retrospective analysis of pediatric renal transplant patients receiving 24 weeks valganciclovir prophylaxis (15 mg/kg/day, maximum 900 mg/day) from January 2004 to December 2008, aiming to measure the incidence of CMV disease and toxicity of valganciclovir. Results. We enrolled 111 patients, 60% males, 46% African Americans, and median age at transplant 14.5 years (range 1.4–20.4 years). Sixty-nine percent of donors and 44% of recipients were seropositive pretransplant. Median duration of valganciclovir use was 5.9 months (range 0.5–24 months). CMV viremia and disease occurred in 27% and 4.5%, respectively. All patients with disease presented after prophylaxis ended and all were D+/R−. Thymoglobulin use (P=0.04) and positive donor CMV status (P=0.02) were associated with a higher risk of CMV viremia. Twenty-four percent had hematologic toxicity directly associated with valganciclovir. Conclusions. Valganciclovir use in children was effective as prophylaxis against CMV disease; no children at our institution developed disease while on therapy. Our regimen of 24 weeks of prophylaxis was associated with a lower rate of late-onset disease than previous reports with 12-week regimens. Further controlled studies should be considered to compare longer versus shorter periods of prophylaxis and dose reductions and their impact on prevention of late-onset disease, resistance, cost, and toxicity.

Linear growth in pediatric renal transplant recipients receiving sirolimus

Hymes LC, Warshaw BL. Linear growth in pediatric renal transplant recipients receiving sirolimus.
Pediatr Transplantation 2011: 15: 570–572.

Long-term outcome of patients with obstructive uropathy.

The effects of obstruction on renal development and the pathophysiology of acute and chronic obstruction in the fully developed kidney are summarized in order to provide the proper anatomic and physiologic framework for a discussion of our current knowledge of the long-term outcome of children with obstructive uropathy. The article also examines some of the mechanisms that may be responsible for deterioration of renal function despite satisfactory relief of obstruction.