BK nephropathy in pediatric hematopoietic stem cell transplant recipients

Risk factors for BK virus-associated hemorrhagic cystitis after allogeneic hematopoietic stem cell transplantation: A systematic review and meta-analysis

OBJECTIVE AND BACKGROUND

BK virus-associated hemorrhagic cystitis (BKV-HC) is an intractable complication leading to higher mortality and prolonged hospitalization among allogeneic hematopoietic stem cell transplantation (allo-HCT) recipients. Therefore, identifying the potential risk factors of BKV-HC after allo-HCT is crucial to improve prognosis and for early prevention. However, the risk factors for BKV-HC remain debatable. Therefore, we conducted a systematic review and meta-analysis to identify the risk factors for BKV-HC, for early prevention of the occurrence of BKV-HC and to improve the quality of life and prognosis of allo-HCT recipients.

METHODS

We searched relevant studies from PubMed, EMBASE, and the Cochrane Library up to February 2023. The odds ratios (ORs) and the corresponding 95% confidence intervals (CIs) of all risk factors were calculated to evaluate their effects on the occurrence of BKV-HC.

RESULTS

Overall, 11 studies involving 2556 allo-HCT recipients were included in this meta-analysis. All included studies were retrospective and published between 2013 and 2022. We found that male sex (OR = 1.32; 95% CI, 1.07-1.62; p = .009, I2  = 34%), haploidentical donor (OR = 1.84; 95% CI, 1.18-2.87; p = .007, I2  = 23%), myeloablative conditioning (OR = 1.76; 95% CI, 1.36-2.28; p < .0001, I2  = 45%), acute graft versus host disease (aGVHD) (OR = 2.73; 95% CI, 2.02-3.69; p < .0001, I2  = 46%), chronic graft versus host disease (cGVHD) (OR = 1.71; 95% CI, 1.12-2.60; p = .01, I2  = 0%), and cytomegalovirus (CMV) reactivation (OR = 3.13; 95% CI, 1.12-8.78; p = .03, I2  = 79%) were significantly associated with BKV-HC in the univariable analysis.

CONCLUSIONS

Our meta-analysis indicated that male sex, haploidentical donor, myeloablative conditioning, aGVHD, cGVHD, and CMV reactivation were potential risk factors for BKV-HC.

BK Viremia and Changes in Estimated Glomerular Filtration Rate in Children and Young Adults after Hematopoietic Cell Transplantation

Kidney disease in allogeneic hematopoietic cell transplantation (HCT) recipients is associated with increased mortality rates. BK virus (BKV) viremia has been associated with kidney dysfunction in pediatric HCT recipients; however, few studies have investigated longer-term kidney outcomes in association with BKV in this population. Here we assessed the relationship between BK viremia and changes in estimated glomerular filtration rate (eGFR) in children in the first year post-HCT. We selected 136 patients age ≤26 years who underwent HCT in 2007 to 2018 at a single center and had plasma BK viral load data available at 2 time points, weeks 4 to 7 post-HCT and weeks 10 to 13 post-HCT from prospectively collected stored plasma samples. A total of 272 samples were analyzed for BKV using quantitative PCR. We used multivariate linear models to determine the association of BK viremia and change in eGFR by 1 year post-HCT. Forty percent of the patients (54 of 136) had BKV detection in weeks 4 to 7, 13% of whom (7 of 54) had a BK viral load of ≥10,000 copies/mL, and 46% (62 of 136) had BKV detected in weeks 10 to 13, 34% (21 of 62) of whom had a BK viral load of ≥10,000 copies/mL. The mean decline in eGFR was 25.73 mL/min/1.73 m² by 1 year post-HCT. In multivariate models, a BK viral load of ≥10,000 copies/mL during weeks 4 to 7 was associated with a mean decline in eGFR of 30.6 mL/min/1.73 m² (95% confidence interval, -55.94 to -5.17; P = .019) compared with a BK viral load <10,000 copies/mL. In adjusted analyses, a high BK viral load in the blood (≥10,000 copies/mL) was associated with a significant decline in eGFR by 1 year post-HCT.

Long-Term Health Effects of Curative Therapies on Heart, Lungs, and Kidneys for Individuals with Sickle Cell Disease Compared to Those with Hematologic Malignancies

The goal of curing children and adults with sickle cell disease (SCD) is to maximize benefits and minimize intermediate and long-term adverse outcomes so that individuals can live an average life span with a high quality of life. While greater than 2000 individuals with SCD have been treated with curative therapy, systematic studies have not been performed to evaluate the long-term health effects of hematopoietic stem cell transplant (HSCT) in this population. Individuals with SCD suffer progressive heart, lung, and kidney disease prior to curative therapy. In adults, these sequalae are associated with earlier death. In comparison, individuals who undergo HSCT for cancer are heavily pretreated with chemotherapy, resulting in potential acute and chronic heart, lung, and kidney disease. The long-term health effects on the heart, lung, and kidney for children and adults undergoing HSCT for cancer have been extensively investigated. These studies provide the best available data to extrapolate the possible late health effects after curative therapy for SCD. Future research is needed to evaluate whether HSCT abates, stabilizes, or exacerbates heart, lung, kidney, and other diseases in children and adults with SCD receiving myeloablative and non-myeloablative conditioning regimens for curative therapy.

BK virus encephalitis and end-stage renal disease in a child with hematopoietic stem cell transplantation

BK virus encephalitis after HSCT is uncommon. Several reports of native kidney BKVN in patients with HSCT, hematologic malignancies, human immunodeficiency virus infection, and non-renal solid organ transplantation have been described. However, an uncommon combination of BK encephalitis and ESRD of native kidneys secondary to BK virus in a child with HSCT has not been described. We report a 10-year-old boy who presented with a gradually rising serum creatinine during treatment for severe autoimmune hemolytic anemia, which he developed 9 months after receiving an allogeneic HSCT for aplastic anemia. There was no proteinuria or hematuria present. Serum BK virus load was 5 × 10⁶  copies/mL. A renal biopsy showed evidence of BKVN. He developed fever, seizures, and confusion, and the (CSF) showed significant presence of the BK virus (1 × 10⁶  copies/mL) along with biochemical evidence of viral encephalitis. Cerebrospinal fluid cultures were negative. Despite significant clinical symptoms and presence of BK virus in CSF, the magnetic resonance brain imaging findings were minimal. With reduction of immunosuppression, there was resolution of BK encephalitis but BKVN remained resistant to multiple anti-BK virus agents, including leflunomide and cidofovir. He eventually became dialysis-dependent and, 6 years later, received a renal transplant from his mother. This case illustrates that BK virus in severely immunocompromised HSCT recipient may lead to BK encephalitis and BKVN of native kidneys, even without hemorrhagic cystitis, leading to ESRD. Knowledge of such is important for appropriate timely evaluation and management.

Optimal Delivery of Follow-Up Care After Allogeneic Hematopoietic Stem-Cell Transplant: Improving Patient Outcomes with a Multidisciplinary Approach

The increasing indications for allogeneic stem-cell transplant in patients with hematologic malignancies and non-malignant diseases combined with improved clinical outcomes have contributed to increase the number of long-term survivors. However, survivors are at increased risk of developing a unique set of complications and late effects, besides graft-versus-host disease and disease relapse. In this setting, the management capacity of a single health-care provider can easily be overwhelmed. Thus, to provide appropriate survivorship care, a multidisciplinary approach for the long-term follow-up is essential. This review aims at summarizing the most relevant information that a health-care provider should know to establish a follow-up care plan, in the light of individual exposures and risk factors, that includes all organ systems and considers the psychological burden of these patients.

Pathogenicity of BK virus on the urinary system

Introduction

The polyomaviruses are omnipresent in nature. The major sites of BK virus appearance are the kidney tubular epithelial cells and urinary bladder surface transitional cells.

Material and methods

A literature search according to PRISMA guidelines within the Medline database was conducted in July 2019 for articles presenting data about BK virus in urologic aspect without setting time limits, using the terms ‘BK virus’ in conjunction with transplantation, nephropathy, stenosis, cancer, bladder, prostate, kidney.

Results

The BK virus usually stays latent, however, its replication may become active in various clinical situations of impaired immunocompetence such as solid organ transplantation, bone marrow transplantation, AIDS, pregnancy, multiple sclerosis, administration of chemotherapy or biologic therapy. BK virus is associated with two main complications after transplantation: polyomavirus-associated nephropathy in kidney transplant patients and polyomavirus-associated hemorrhagic cystitis in allogeneic hematopoietic stem cell transplant patients.

Conclusions

The aim of this article was to present available data on urologic aspects of BK virus infection, its detection methods and available treatment.

BK polyoma virus nephropathy in hematopoietic cell transplant recipients

Background:

The epidemiology of BK polyoma virus nephropathy in hematopoietic cell transplant recipients is poorly characterized. Kidney dysfunction after hematopoietic cell transplant is often attributed to treatment toxicities and kidney biopsies are rarely performed.

Methods:

We reviewed pathology-confirmed BK polyoma virus nephropathy cases in adult and pediatric patients who had undergone a hematopoietic cell transplant between 1 January 2015 and 31 December 2017 at our institution. Plasma and urine BK polyoma virus was assessed by a quantitative polymerase chain reaction assay and were obtained at the clinician discretion. Glomerular filtration rate was estimated by the Chronic Kidney Disease Epidemiology Collaboration equation. BK polyoma virus nephropathy was scored by the Banff Working Group Proposal.

Results:

Eight (7 adult and 1 pediatric) cases of BK polyoma virus nephropathy were identified among 685 hematopoietic cell transplant recipients, 14 of whom had undergone a kidney biopsy. Five patients (62.5%) had received a CD34+-selected peripheral blood hematopoietic cell transplant; two had received a cord blood allograft and one an unmodified peripheral blood hematopoietic cell transplant. Two patients developed acute graft-versus-host disease grade II. Early post–hematopoietic cell transplant BK polyoma viruria was documented with onset at a median of 54 days (range, 6–91) post–hematopoietic cell transplant and median urine BK polyoma viral load was 9.6 log10 copies/mL (range, 8.6–10.0). BK polyoma virus nephropathy was diagnosed at a median of 267 days after hematopoietic cell transplant (range, 133–637). At BK polyoma virus nephropathy diagnosis, all patients had decreased renal function with glomerular filtration rate (median 29 mL/min/1.73 m2; range, 9–98 ) and creatinine (median 2.4 mg/dL; range, 0.8–7.5) ; median plasma BK polyoma viral load was 6.3 log10 copies/mL (range, 5.5–7.1) and median CD4+ lymphocyte count was 82 cell/mcL (range, 21–172).

Conclusions:

We report eight biopsy-proven BK polyoma virus nephropathies in hematopoietic cell transplant recipients from a single center. BK polyoma virus nephropathy should be considered in hematopoietic cell transplant recipients with worsening kidney function and high BK polyoma viremia.

Native kidney BK virus nephropathy, a systematic review

BACKGROUND

There is a growing base of literature describing BK nephropathy (BKVN) in patients outside of the setting of kidney transplant. Previous systematic reviews of the literature have been limited by methodology or by the scope of patients included.

STUDY DESIGN AND METHODS

Systematic Review (Prospero # CRD42018088524).

SETTING & POPULATION

Patients without kidney transplant who had biopsy-proven BKVN.

SELECTION CRITERIA FOR STUDIES

Full-text articles that describe native BKVN patient cases.

ANALYTICAL APPROACH

Descriptive synthesis.

RESULTS

The search identified 630 unique articles of which 51 were included in the final review. Sixty-five cases (including two new cases presented in this review) were identified, all but one occurred in the setting of known immunosuppression.

LIMITATIONS

The primary limitation was the exclusion of studies that did not fulfill the stringent review criteria. We excluded reports with only a clinical diagnosis of BKVN, such as those with viruria and/or viremia without biopsy.

CONCLUSIONS

As of May 2018, there are 65 reported cases of BKVN in native kidneys. This represents the most comprehensive description of biopsy-proven BKVN in native kidneys to date. Evaluation for BK nephropathy should be considered in immunocompromised patients who exhibit unexplained renal failure.

The impact of recipient BKV shedding before transplant on BKV viruria, DNAemia, and nephropathy post-transplant: A prospective study

We previously demonstrated that detectable BKV replication in donor urine pretransplant was significantly associated with post-transplant recipient BKV viremia. In this 4-year prospective study, we assessed whether recipient BKV replication pretransplant was associated with post-transplant viremia/BKV nephropathy. We studied 220 primary adult and pediatric organ transplant recipients for 490 person-years and 2100 clinical visits. BKV viruria was detectable in 28 (16%), 26 adults and two children; and viremia in none pretransplant. Post-transplant viruria occurred in all recipients with pretransplant BKV viruria, significantly more than in recipients without pretransplant viruria on univariate (P<.005) and multivariate analysis including type of organ transplanted and immunosuppression type (P .008). Time to post-transplant viruria was significantly shorter in recipients with pretransplant viruria (P .01). By univariate and multivariate analysis, BKV viruria in recipients pretransplant did not impact post-transplant BKV viremia (P=.97 and .97, respectively) even when stratified by type of organ transplant (kidney P=.6; liver P=.5). The peak serum and urine BKV PCR post-transplant were not significantly different in patients with pretransplant BKV viruria and no one developed BK nephropathy. In conclusion, recipient BKV viruria prior to transplant predicts post-transplant viruria but not viremia or BKV nephropathy.

The Noninvasive Urinary Polyomavirus Haufen Test Predicts BK Virus Nephropathy in Children After Hematopoietic Cell Transplantation: A Pilot Study

BACKGROUND

After hematopoietic cell transplantation (HCT), polyoma-BK virus is associated with hemorrhagic cystitis and also with polyomavirus nephropathy (PVN). However, the true burden of post-HCT PVN is unknown because kidney biopsies are avoided due to their bleeding risk. The novel, noninvasive urinary PV-Haufen test detects PVN in kidney transplant recipients with greater than 95% positive/negative predictive values. We hypothesized that the detection of PV-Haufen in voided urine samples-a positive PV-Haufen test-was also clinically significant after HCT.

METHODS

We examined 21 suitable urine samples from 14 patients (median age, 15 years; 71.4% male) who were selected from repositories for having varying degrees of BK viremia (range, 0-1.0 × 10 copies/mL), hemorrhagic cystitis (present/absent), and data on kidney function. Urine samples were obtained at a median of 88 days post-HCT.

RESULTS

The PV-Haufen were detected in 5 of 14 patients (35.7%) and 7 of 21 (33.3%) urine samples, with histologic confirmation of PVN in 1 autopsy specimen. After a median of 285 days post-HCT, patients with PV-Haufen had an increased risk of dialysis-dependent renal failure (P < 0.05). All 3 dialysis-dependent patients had PV-Haufen and died. The presence of urinary PV-Haufen was not significantly correlated with hemorrhagic cystitis. From the 16 urines collected during BK viremia, 43.8% were PV-Haufen-positive, and 56.2% were negative. The PV-Haufen were not present in the 5 urines from patients without concomitant BK-viremia.

CONCLUSIONS

In this proof-of-concept study, a positive PV-Haufen test was only seen in some patients with BK viremia and was not associated with hemorrhagic cystitis. The detection of PV-Haufen suggests underlying PVN with an increased risk of kidney failure and dialysis.

Late effects of blood and marrow transplantation

Hematopoietic cell transplantation is a curative treatment for a variety of hematologic diseases. Advances in transplantation technology have reduced early transplant-related mortality and expanded application of transplantation to older patients and to a wider variety of diseases. Management of late effects after transplantation is increasingly important for a growing number of long-term survivors that is estimated to be half a million worldwide. Many studies have shown that transplant survivors suffer from significant late effects that adversely affect morbidity, mortality, working status and quality of life. Late effects include diseases of the cardiovascular, pulmonary, and endocrine systems, dysfunction of the thyroid gland, gonads, liver and kidneys, infertility, iron overload, bone diseases, infection, solid cancer, and neuropsychological effects. The leading causes of late mortality include recurrent malignancy, lung diseases, infection, secondary cancers and chronic graft-versus-host disease. The aim of this review is to facilitate better care of adult transplant survivors by summarizing accumulated evidence, new insights, and practical information about individual late effects. Further research is needed to understand the biology of late effects allowing better prevention and treatment strategies to be developed.

BK nephropathy in the native kidneys of patients with organ transplants: Clinical spectrum of BK infection

Nephropathy secondary to BK virus, a member of the Papoviridae family of viruses, has been recognized for some time as an important cause of allograft dysfunction in renal transplant recipients. In recent times, BK nephropathy (BKN) of the native kidneys has being increasingly recognized as a cause of chronic kidney disease in patients with solid organ transplants, bone marrow transplants and in patients with other clinical entities associated with immunosuppression. In such patients renal dysfunction is often attributed to other factors including nephrotoxicity of medications used to prevent rejection of the transplanted organs. Renal biopsy is required for the diagnosis of BKN. Quantitation of the BK viral load in blood and urine are surrogate diagnostic methods. The treatment of BKN is based on reduction of the immunosuppressive medications. Several compounds have shown antiviral activity, but have not consistently shown to have beneficial effects in BKN. In addition to BKN, BK viral infection can cause severe urinary bladder cystitis, ureteritis and urinary tract obstruction as well as manifestations in other organ systems including the central nervous system, the respiratory system, the gastrointestinal system and the hematopoietic system. BK viral infection has also been implicated in tumorigenesis. The spectrum of clinical manifestations from BK infection and infection from other members of the Papoviridae family is widening. Prevention and treatment of BK infection and infections from other Papovaviruses are subjects of intense research.

Risks and Epidemiology of Infections After Hematopoietic Stem Cell Transplantation

Infections following HCT are frequently related to risk factors caused by the procedure itself. Neutropenia and mucositis predispose to bacterial infections. Prolonged neutropenia increases the likelihood of invasive fungal infection. GVHD and its treatment create the most important easily identifiable risk period for a variety of infectious complications, particularly mold infections. Profound, prolonged T cell immunodeficiency, present after T cell-depleted or cord blood transplants, is the main risk factor for viral problems like disseminated adenovirus disease or EBV-related posttransplant lymphoproliferative disorder.

Review article: BK virus in systemic lupus erythematosus

BK virus (BKV) is a human polyomavirus with a seroprevalence of 60-80 % in the general population. In renal transplant patients, it is known to cause renal failure, ureteric stenosis and hemorrhagic cystitis. In bone marrow transplant patients, it is evident that BKV can also cause hemorrhagic cystitis along with BK virus nephropathy (BKVN) in the native kidneys, with subsequent renal failure. However, little is known about BVKN in non-transplanted immune-compromised patients, such as systemic lupus erythematosus (SLE) who may have underlying nephritis and have a compromised immune system due to therapy and/or systemic illness. Thus, this article will focus on the clinical aspects of BKV and its association in patients with SLE.

BK virus nephropathy in a pediatric patient after hematopoietic stem cell transplantation

We report the case of a seven-yr-old Caucasian girl who presented with progressive deterioration of renal function 13 months after HSCT for myelodysplastic syndrome. BK virus nephropathy was suspected and confirmed. After reduction of immunosuppression and treatment with IVIG, leflunomide, ciprofloxacin, and cidofovir, clearance of BK virus from blood was achieved, and further progression or renal failure was prevented. We believe that BK virus nephropathy should be considered in cases of renal function deterioration in all immunocompromised patients.

Brincidofovir for polyomavirus-associated nephropathy after allogeneic hematopoietic stem cell transplantation

Polyomavirus-associated nephropathy (PVAN) is common in patients who have undergone kidney transplantation and has been reported in hematopoietic stem cell (HSC) transplant recipients. Aside from reduction of immunosuppression, few therapeutic options exist for treatment of PVAN. We report a case of PVAN in a severely immunocompromised allogeneic HSC transplant recipient that was treated with brincidofovir without reduction of immunosuppression. We review our institutional experience of PVAN in HSC transplantation and discuss the potential use of brincidofovir for treatment.

Renal pathology associated with hematopoietic stem cell transplantation

The kidney is subject to a large variety of injurious factors before, during, and after hematopoietic stem cell transplantation (HCT), leading to a high incidence of acute kidney injury in the peritransplant period. Chronic kidney disease is estimated to impact 15% to 20% of HCT recipients. Although renal biopsies may be deferred in the setting of thrombotic microangiopathy, acute self-limited impairment, or slowly progressive functional decline, in many patients renal biopsy yields important diagnostic insight to guide treatment. Light microscopic, immunofluorescence, and ultrastructural analysis often reveals a number of concurrent abnormalities in glomeruli, tubules, interstitium, and vessels. Meta-analysis of the literature reveals that membranous nephropathy is the most commonly reported glomerular lesion in the setting of HCT, followed by minimal change disease. Autopsy and biopsy studies show that clinical criteria lack sensitivity and specificity for renal acute and chronic thrombotic microangiopathy. Viral infection and other causes of interstitial nephritis and tubular injury are important findings in HCT renal biopsies, which in many instances may not be clinically suspected. Given the complexity and variability of HCT protocols, clinicopathologic correlation is needed.

Kidney and bladder outcomes in children with hemorrhagic cystitis and BK virus infection after allogeneic hematopoietic stem cell transplantation

BK virus (BKV) infection is associated with hemorrhagic cystitis (HC) in hematopoietic stem cell transplantation (HSCT) recipients and nephropathy after kidney transplantation. We assessed the association between BKV and kidney and bladder complications in children developing HC by retrospectively reviewing 221 consecutive pediatric allogeneic HSCT recipients at the Children's Hospital of Philadelphia from 2005 to 2011. We included all patients with BKV PCR testing performed for clinical indication from day 0 until 1 year post-HSCT (N = 68). We assessed the association of any BKV infection (urine and/or blood) or peak BK viremia ≥ 10,000 copies/mL (high viremia) with severe HC (defined as grade IV-bladder catheterization or surgical intervention); the need for dialysis; serum creatinine-estimated glomerular filtration rate at the time of BKV testing, day 100, and day 365; and death. Children with high viremia more likely developed severe HC compared with those with peak viremia < 10,000 copies/mL (21% versus 2%; P = .02). BKV infection of the blood or urine was not associated with the need for dialysis, change in estimated glomerular filtration rate, or mortality. BKV infection is common after pediatric allogeneic HSCT, and plasma testing in those with HC may predict patients who will develop severe bladder injury.

Treatment of BK virus-associated hemorrhagic cystitis in pediatric hematopoietic stem cell transplant recipients with cidofovir: a single-center experience

BACKGROUND

BK virus (BKV)-associated hemorrhagic cystitis (BKV-HC) is a severe complication after hematopoietic stem cell transplantation (HSCT). Cidofovir (CDV) has emerged as an effective agent for the treatment of BKV nephropathy, but its use for BKV-HC in pediatric HSCT recipients has not yet been established as a standard therapy.

PATIENT AND METHODS

We retrospectively investigated the efficacy and safety of CDV therapy for patients with BKV-HC at a single institution and analyzed the clinical management outcomes.

RESULTS

From April 2009 to July 2011, 12 patients developed BKV-HC at a median of 37 days after transplant (range 15-59 days). The cumulative incidence was 9% and the median peak of the urine BKV load was 2.5 × 10(10) copies/mL (range 1.4 × 10(9) -1.2 × 10(11) copies/mL). Eleven patients received intravenous CDV (5 mg/kg/dose, with probenecid), whereas 1 patient received CDV (5 mg/kg/dose, without probenecid) intravesically. The median duration of therapy was 25 days (range 9-73 days), and a median of 2 doses was given (range 1-4). A reduction of ≥ 1 log in the BKV load was found in 11 patients, while 1 patient did not have any significant change in BKV load. Clinical improvement was observed in all cases, and no HC-related death was observed. CDV-related toxicity occurred in 1 patient (8%) and spontaneously resolved.

CONCLUSIONS

CDV appears to be an effective and safe treatment for BKV-HC in pediatric HSCT recipients, but prospective trials are warranted to support its use.

BK virus nephropathy in a pediatric heart transplant recipient with post-transplant lymphoproliferative disorder: a case report and review of literature

BKV is known to cause allograft failure in kidney transplant recipients. It has been recently recognized to cause native kidney nephropathy in non-kidney transplant recipients. This is a case report BKVN in a 15-yr-old HTx recipient who had PTLD and a review of pediatric cases in the literature. The patient was diagnosed with BKVN +189 months after transplantation and died thirty days after diagnosis of BKVN. We identified five other cases of BKVN in pediatric non-kidney solid organ transplantation, of which all were HTx recipients. Overall, outcome was poor and BKV clearance was not achieved with reduction of immunosuppression and with current therapies. We strongly recommend that pediatric HTx recipients be tested for BKV infection if there is evidence of kidney dysfunction. We also recommend that they have an annual screening for BKV viruria and viremia with the assessment of kidney function.

Unusual presentations of BK virus infections in pediatric renal transplant recipients

BKV has emerged as a significant pathogen in the field of transplantation, predominantly causing BKV nephropathy in renal transplant recipients and hemorrhagic cystitis in HSCT recipients. However, case reports describe more diverse complications, and we too present three unusual cases of BKV infections in pediatric renal transplant recipients. First, we describe a case of biopsy-proven renal damage secondary to BKV prior to the onset of viremia, demonstrating that BKV nephropathy can occur without preceding viremia. We also present two renal transplant recipients with persistent BK viruria, one with BKV-associated hemorrhagic cystitis and the other with microscopic hematuria. Therefore, we conclude that BKV manifestations may be more diverse than previously thought and suggest clinical utility in urine BKV qPCR testing in specific transplant recipients.

BK polyoma virus nephropathy in the native kidney

BACKGROUND

While BK polyoma virus nephropathy (PVN) is a well-recognized cause of renal allograft dysfunction, PVN of native kidneys is likely under-recognized.

METHODS

We present the pathologic features, risk factors and outcomes of eight cases of PVN in native kidneys.

RESULTS

The cohort included eight males aged 16-73 years (mean 47.4) with an immunocompromised state (mean duration 3.15 years) attributable to: hematologic malignancies (n = 6), for which three had undergone bone marrow transplant; lung transplant (n = 1) and combined tuberculosis and diabetes (n = 1). Seven patients were receiving specific immunosuppressive therapies. Patients were biopsied for acute kidney injury (AKI) with rise in mean creatinine levels from baseline 1.6 to 2.8 mg/dL. Pathology showed BK PVN with characteristic intranuclear inclusions staining positive for SV40 T antigen and negative for JC virus (JCV), with positive serum and/or urine PCR for BK virus. One patient had focal medullary JCV co-infection. Two patients also had renal infiltration by chronic lymphocytic leukemia (CLL). Six patients received specific therapy directed to PVN (cidofovir or leflunomide). Follow-up ranged from 2 to 20 (mean 10) months. Despite marked decrease in serum BK viral copy numbers, creatinine continued to rise in six cases (mean 3.7 mg/dL in four, requiring dialysis in two) and three patients died of malignancy, opportunistic infection or renal failure. Advanced histologic stage of PVN, ineffective antiviral therapy, co-morbidities and persistent immunocompromised state likely contributed to the poor outcomes.

CONCLUSION

A high level of suspicion in immunocompromised patients is needed to diagnose PVN in an early stage that may respond more favorably to antiviral therapy.

Chronic kidney diseases in long-term survivors after allogeneic hematopoietic stem cell transplantation: monitoring and management guidelines

Chronic kidney disease (CKD) occurs commonly (prevalence of approximately 20% in a large series) after allogeneic hematopoietic stem cell transplantation (HSCT). There are three distinct clinical entities that occur after HSCT: thrombotic microangiopathy (TMA), nephrotic syndrome (NS), and idiopathic or graft-versus-host disease (GVHD)-related CKD. Acute renal function decline occurs in the majority of patients in the first months after transplantation. This acute kidney injury can persist and is a risk factor for the later development of CKD. However, the potentially independent role of GVHD, chronic inflammation, and chronic exposure to calcineurin inhibitors in the development and progression of CKD warrants further investigation. Careful monitoring of blood pressure, renal function, and proteinuria is mandatory in patients undergoing HSCT, especially older patients with pre-existent renal impairment. Renal function should be evaluated before HSCT and monitoring should occur at least every 6 to 12 months in these patients. Renal biopsies are indicated in patients with proteinuria and persistent or progressive rises in serum creatinine to determine etiology and prevent progression to end-stage renal disease (ESRD).

BK polyomavirus: emerging pathogen

BK polyomavirus (BKPyV) is a small double-stranded DNA virus that is an emerging pathogen in immunocompromised individuals. BKPyV is widespread in the general population, but primarily causes disease when immune suppression leads to reactivation of latent virus. Polyomavirus-associated nephropathy and hemorrhagic cystitis in renal and bone marrow transplant patients, respectively, are the most common diseases associated with BKPyV reactivation and lytic infection. In this review, we discuss the clinical relevance, effects on the host, virus life cycle, and current treatment protocols.

Blood, and not urine, BK viral load predicts renal outcome in children with hemorrhagic cystitis following hematopoietic stem cell transplantation

BK virus is a significant cause of hemorrhagic cystitis after hematopoietic stem cell transplantation (HSCT). However, its role in nephropathy post-HSCT is less studied. We retrospectively evaluated clinical outcomes in pediatric HSCT patients with hemorrhagic cystitis. Although most of these patients had very high urine BK viral loads (viruria), patients with higher BK plasma loads (viremia) had significant renal dysfunction, a worse clinical course, and decreased survival. Patients with a peak plasma BK viral load of >10,000 copies/mL (high viremia) were more likely to need dialysis and aggressive treatment for hemorrhagic cystitis compared to patients with ≤ 10,000 copies/mL (low viremia). Conversely, most patients with low viremia had only transient elevations in creatinine, and less severe hemorrhagic cystitis that resolved with supportive therapy. Overall survival (OS) at 1 year post-HSCT was 89% in the low viremia group and 48% in the high viremia group. We conclude that the degree of BK viremia, and not viruria, may predict renal, urologic, and overall outcome in the post-HSCT population.

BK virus nephropathy in a pediatric autologous stem-cell transplant recipient

BK virus (BKV) is an increasingly identified cause of pathology in immunocompromised transplant recipients. BKV is a well-known cause of graft dysfunction following renal transplantation and has also been reported in the native kidneys of other solid organ recipients. Less commonly, BKV nephropathy occurs in allogeneic stem-cell transplant (SCT) recipients. We now describe the first reported case of BKV nephropathy after pediatric autologous SCT.

Hematopoietic cell transplantation and emerging viral infections

Viral infections remain important causes of morbidity and mortality in hematopoietic cell transplant recipients. More recent developments in preparative regimens and graft manipulations, as well as the control of well-recognized post-transplant infections by the introduction of prophylaxis and preemptive strategies, have influenced the timing and the epidemiology of infections. As new pathogens, such as human metapneumovirus (HMPV), human bocavirus, human coronaviruses HCoV-NL63 and HCoV-HKU1, human herpesviruses HHV-6 and HHV-7, and polyomaviruses, have emerged, it is fundamental to determine the significance of the newly discovered viruses and their role in the transplantation field. This article summarizes recent data on epidemiology and laboratory diagnosis of new pathogens, as well as clinical features and management of the associated infectious complications. J. Med. Virol. 82:528-538, 2010. (c) 2010 Wiley-Liss, Inc.