The glomerulopathy of sickle cell disease

Prevalence and associated factors of glomerular hyperfiltration among adult stable sickle cells in Kinshasa, DR Congo

INTRODUCTION

Glomerular hyperfiltration is highly frequent, theoretically dependent on cardiac output, low systemic vascular resistance and hemolysis markers. In sickle cell disease (SCD), hyperfiltration is an extremely common phenomenon and occurred in young and early adult patients. Despite the fact that the glomerular hyperfiltration is known as the early manifestations of sickle cell nephropathy, its burden among adult sickle cell disease in sub-Saharan is poor studied. This study aimed to determine the prevalence and associated factors of hyperfiltration.

METHODS

This was an analytical multicentric cross-sectional study involving stable adult sickle cell patients in Kinshasa, recruited between March and October 2023. Parameters of interest encompasses demographic, clinical, biological, echocardiographic and pulse wave measurement data. Hyperfiltration was defined using the CDK-EPI equation based on cystatin C; eGFR >130 for women and >140 ml/min/1.73m2 for men. We used multivariate logistic regression analysis to search determinants of glomerular hyperfiltration.

RESULTS

Two hundred and fourty six (246) patients with SCD were enrolled. The prevalence of hyperfiltration was 20.7%. In multiple logistic regression analysis, hyperfiltration status was independently associated with age (< 25 years) [3.57 (1.78-7.49); p = 0.027)], female sex [4.36 (2.55-5.62); p = 0.031), CRP (< 6 mg/l) [0.77 (0.61-0.97); p = 0.028)], central systolic pressure (< 100 mmHg) and central diastolic pressure (< 60 mmHg) [0.86(0.74-0.98), p = 0.028)], [(0.83 (0.71-0.98); p = 0.032)].

CONCLUSION

One out of five SS adults exhibits hyperfiltration, which is associated with young age and female sex, whereas low CRP and blood pressure were negative risk factors.

Association of biomarkers of endothelial function, coagulation activation and kidney injury with persistent albuminuria in sickle cell anaemia

Persistent albuminuria (PA) is common in sickle cell anaemia (SCA). With the association of chronic kidney disease (CKD) with increased mortality, biomarkers that predict its development or progression are needed. We evaluated the association of select biomarkers with PA in adults with SCA using Kruskal-Wallis rank-sum test and logistic regression models, with adjustment for multiple testing. Of 280 subjects, 100 (35.7%) had PA. Median plasma levels of soluble vascular cell adhesion molecule-1 (VCAM-1) (1176.3 vs. 953.4 ng/mL, false discovery rate [FDR] q-value <0.003), thrombin-antithrombin complex (5.5 vs. 4.7 ng/mL, FDR q-value = 0.04), and urinary angiotensinogen (AGT) (12.2 vs. 5.3 ng/mg, FDR q-value <0.003), urinary nephrin (30.6 vs. 27.2 ng/mg, FDR q-value = 0.04), and urinary kidney injury molecule-1 (KIM-1) (0.8 vs. 0.5 ng/mg, FDR q-value <0.003), normalized to urine creatinine, were significantly higher in subjects with PA. In multivariable analysis, only urinary AGT (odds ratio = 1.058, FDR q-value <0.0001) remained a significant predictor of PA. In addition, soluble VCAM-1 (FDR q-value <0.0001), D-dimer (FDR q-value <0.0001), urinary AGT (FDR q-value <0.0001), KIM-1 (FDR q-value <0.0001), and nephrin (FDR q-value <0.0001) were significantly associated with urine albumin-creatinine ratio in multivariable analyses. Longitudinal studies to evaluate the predictive capacity of biomarkers for the development and progression of CKD in SCA are warranted.

Persistent albuminuria and chronic kidney disease in adults with sickle cell anaemia: Results from a multicenter natural history study

Clinical and laboratory correlates of chronic kidney disease (CKD) in sickle cell anaemia remain incompletely defined. In a multicenter cohort study, we evaluated the prevalence of persistent albuminuria (PA) and characteristics associated with PA, albumin-creatinine ratio (ACR) and decreased estimated glomerular filtration rate (eGFR) using logistic, linear and multinomial regression models, respectively. Of 269 participants (median age: 30 years; 57.2% females), the prevalence of PA was 35.7%. Using baseline ACR values of <100 and ≥100 mg/g, the probabilities of PA were 30.0% and 94.6%, respectively. In multivariable logistic regression analyses, male sex (β = 0.80 [SE = 0.36], p = 0.024) and ACE inhibitors/ARBs use (β = 1.54 [SE = 0.43], p < 0.001) were associated with higher likelihoods of PA, while higher haemoglobin (β = -0.33 [SE = 0.13], p = 0.009) and HbF (β = -0.04 [SE = 0.02], p = 0.041) were associated with lower likelihoods of PA. In multivariable multinomial regression analyses, older age (β = 0.06 [SE = 0.02], p = 0.004) and higher alkaline phosphatase (β = 0.01 [SE = 0.00], p = 0.004) were associated with higher odds of having eGFR 60-90 versus eGFR>90 mL/min/1.73 m2 using the cystatin C-based CKD-EPI-2012 equation. Additionally, higher systolic blood pressure (β = 0.11 [SE = 0.03], p = 0.001) and blood urea nitrogen (β = 0.45 [SE = 0.12], p < 0.001) were associated with higher odds, while higher haemoglobin (β = -1.22 [SE = 0.43], p = 0.004) was associated with lower odds of having eGFR<60 versus eGFR>90 mL/min/1.73 m2. PA and decreased eGFR are associated with measures of disease severity and comorbid conditions (Clinicaltrials.gov Identifier: NCT03277547).

End Organ Affection in Sickle Cell Disease

Sickle cell disease is an orphan disease affecting ethnic minorities and characterized by profound systemic manifestations. Although around 100,000 individuals with SCD are living in the US, the exact number of individuals is unknown, and it is considered an orphan disease. This single-gene disorder leads to red blood cell sickling and the deoxygenation of hemoglobin, resulting in hemolysis. SCD is associated with acute complications such as vaso-occlusive crisis, infections, and chronic target organ complications such as pulmonary disease and renal failure. While genetic therapy holds promise to alter the fundamental disease process, the major challenge in the field remains the target end organ damage and ways to mitigate or reverse it. Here, we provide an overview of the clinical manifestations and pathogenesis with a focus on end-organ damage and current therapeutic options, including recent FDA-approved stem cell and gene editing therapies.

Systematic Review of Genetic Modifiers Associated with the Development and/or Progression of Nephropathy in Patients with Sickle Cell Disease

Sickle cell nephropathy (SCN) is a common complication of sickle cell disease (SCD) that significantly contributes to morbidity and mortality. In addition to clinical and life-style factors, genetic variants influence this risk. We performed a systematic review, searching five databases. Studies evaluating the effect of genetic modifiers on SCN were eligible. Twenty-eight studies (fair-to-good quality) were included: one genome-wide association study, twenty-six case-control studies, and one article combining both approaches. APOL1 was significantly associated with albuminuria and hyperfiltration in children and with worse glomerular filtration in adults. On the other hand, alpha-thalassemia protected patients against albuminuria and hyperfiltration, while BCL11A variants were protective against albuminuria alone. The HMOX1 long GT-tandem repeat polymorphism led to a lower glomerular filtration rate. No modifiers for the risk of hyposthenuria were identified. A genome-wide association approach identified three new loci for proteinuria (CRYL1, VWF, and ADAMTS7) and nine loci were linked with eGFR (PKD1L2, TOR2A, CUBN, AGGF1, CYP4B1, CD163, LRP1B, linc02288, and FPGT-TNNI3K/TNNI3K). In conclusion, this systematic review supports the role of genetic modifiers in influencing the risk and progression of SCN. Incorporating and expanding this knowledge is crucial to improving the management and clinical outcomes of patients at risk.

Renal outcomes in pediatric patients with sickle cell disease: a single center experience in Saudi Arabia

Background

Sickle cell nephropathy (SCN) is a significant complication of sickle cell disease (SCD) with an asymptomatic onset in childhood and potential progression to chronic kidney disease (CKD). The clinical findings of SCN include hyposthenuria, hematuria, proteinuria, hyperfiltration, and CKD. Data on renal manifestation among patients with SCD in Saudi Arabia is lacking. Therefore, this study aimed to evaluate renal outcomes in patients with SCD who visited a hematology clinic at the National Guard Hospital, Jeddah.

Methods

We conducted a retrospective chart review of renal complications in patients with SCD who are within 0-14 years of age and on regular follow-ups at the pediatric hematology clinic in King Abdulaziz Medical City-Jeddah, Saudi Arabia.

Results

Among the 140 patients with SCD, 99 met the inclusion criteria. The median age at diagnosis was 18 (1-108) months. Two SCD phenotypes were observed, with 82 (83%) patients having sickle cell anemia (HbSS) and 17 (17%) having HbS/B+ thalassemia. Of the total patients, 92 (93%) were administered hydroxyurea (HU), with a median starting age of 48 (9-168) months. The most common renal complication observed during routine urinalysis was hematuria (38%), followed by proteinuria (11%). After stratifying the sample into four age groups (0-3 years old, 4-7 years old, 8-11 years old, and 12-14 years old), the mean glomerular filtration rate (GFR) values were 96.16, 101.36, 112.69, and 120.11 ml/min/1.73 m2 respectively. Renal imaging revealed abnormal findings in 27 (29%) patients. The most common abnormality observed on US was increased echogenicity (43%).

Conclusion

SCN is a significant complication of SCD. In this study, we assessed the renal outcomes in pediatric patients with SCD. After analyzing the clinical findings of SCN, we concluded that the presence of renal complications in pediatric patients presented a progressive pattern.

Sickle Cell Disease and CKD: An Update

BACKGROUND

Sickle cell disease is an inherited red blood cell disorder that affects approximately 100,000 people in the USA and 25 million people worldwide. Vaso-occlusion and chronic hemolysis lead to dysfunction of vital organ systems, with the kidneys being among the most commonly affected organs.

SUMMARY

Early renal manifestations include medullary ischemia with the loss of urine-concentrating ability and hyperfiltration. This can be followed by progressive damage characterized by persistent albuminuria and a decline in the estimated glomerular filtration rate. The risk of sickle nephropathy is greater in those with the APOL1 G1 and G2 kidney risk variants and variants in HMOX1 and lower in those that coinherit α-thalassemia. Therapies to treat sickle cell disease-related kidney damage focus on sickle cell disease-modifying therapies (e.g., hydroxyurea) or those adopted from the nonsickle cell disease kidney literature (e.g., renin-angiotensin-aldosterone system inhibitors), although data on their clinical efficacy are limited to small studies with short follow-up periods. Kidney transplantation for end-stage kidney disease improves survival compared to hemodialysis but is underutilized in this patient population.

KEY MESSAGES

Kidney disease is a major contributor to early mortality, and more research is needed to understand the pathophysiology and develop targeted therapies to improve kidney health in sickle cell disease.

Interventions for chronic kidney disease in people with sickle cell disease

BACKGROUND

Sickle cell disease (SCD), one of the commonest severe monogenic disorders, is caused by the inheritance of two abnormal haemoglobin (beta-globin) genes. SCD can cause severe pain, significant end-organ damage, pulmonary complications, and premature death. Kidney disease is a frequent and potentially severe complication in people with SCD. Chronic kidney disease (CKD) is defined as abnormalities of kidney structure or function present for more than three months. Sickle cell nephropathy refers to the spectrum of kidney complications in SCD. Glomerular damage is a cause of microalbuminuria and can develop at an early age in children with SCD, with increased prevalence in adulthood. In people with sickle cell nephropathy, outcomes are poor as a result of the progression to proteinuria and chronic kidney insufficiency. Up to 12% of people who develop sickle cell nephropathy will develop end-stage renal disease. This is an update of a review first published in 2017.

OBJECTIVES

To assess the effectiveness of any intervention for preventing or reducing kidney complications or chronic kidney disease in people with sickle cell disease. Possible interventions include red blood cell transfusions, hydroxyurea, and angiotensin-converting enzyme inhibitors (ACEIs), either alone or in combination.

SEARCH METHODS

We searched for relevant trials in the Cochrane Cystic Fibrosis and Genetic Disorders Group Trials Register, CENTRAL, MEDLINE, Embase, seven other databases, and two other trials registers.

SELECTION CRITERIA

Randomised controlled trials (RCTs) comparing interventions to prevent or reduce kidney complications or CKD in people with SCD. We applied no restrictions related to outcomes examined, language, or publication status.

DATA COLLECTION AND ANALYSIS

Two review authors independently assessed trial eligibility, extracted data, assessed the risk of bias, and assessed the certainty of the evidence (GRADE).

MAIN RESULTS

We included three RCTs with 385 participants. We rated the certainty of the evidence as low to very low across different outcomes according to GRADE methodology, downgrading for risk of bias concerns, indirectness, and imprecision. Hydroxyurea versus placebo One RCT published in 2011 compared hydroxyurea to placebo in 193 children aged nine to 18 months. We are unsure if hydroxyurea compared to placebo reduces or prevents progression of kidney disease assessed by change in glomerular filtration rate (mean difference (MD) 0.58 mL/min /1.73 m2, 95% confidence interval (CI) -14.60 to 15.76; 142 participants; very low certainty). Hydroxyurea compared to placebo may improve the ability to concentrate urine (MD 42.23 mOsm/kg, 95% CI 12.14 to 72.32; 178 participants; low certainty), and may make little or no difference to SCD-related serious adverse events, including acute chest syndrome (risk ratio (RR) 0.39, 99% CI 0.13 to 1.16; 193 participants; low certainty), painful crisis (RR 0.68, 99% CI 0.45 to 1.02; 193 participants; low certainty); and hospitalisations (RR 0.83, 99% CI 0.68 to 1.01; 193 participants; low certainty). No deaths occurred in either trial arm and the RCT did not report quality of life. Angiotensin-converting enzyme inhibitors versus placebo One RCT published in 1998 compared an ACEI (captopril) to placebo in 22 adults with normal blood pressure and microalbuminuria. We are unsure if captopril compared to placebo reduces proteinuria (MD -49.00 mg/day, 95% CI -124.10 to 26.10; 22 participants; very low certainty). We are unsure if captopril reduces or prevents kidney disease as measured by creatinine clearance; the trial authors stated that creatinine clearance remained constant over six months in both groups, but provided no comparative data (very low certainty). The RCT did not report serious adverse events, all-cause mortality, or quality of life. Angiotensin-converting enzyme inhibitors versus vitamin C One RCT published in 2020 compared an ACEI (lisinopril) with vitamin C in 170 children aged one to 18 years with normal blood pressure and microalbuminuria. It reported no data we could analyse. We are unsure if lisinopril compared to vitamin C reduces proteinuria in this population: the large drop in microalbuminuria in both arms of the trial after only one month on treatment may have been due to an overestimation of microalbuminuria at baseline rather than a true effect. The RCT did not report serious adverse events, all-cause mortality, or quality of life.

AUTHORS' CONCLUSIONS

We are unsure if hydroxyurea improves glomerular filtration rate or reduces hyperfiltration in children aged nine to 18 months, but it may improve their ability to concentrate urine and may make little or no difference to the incidence of acute chest syndrome, painful crises, and hospitalisations. We are unsure if ACEI compared to placebo has any effect on preventing or reducing kidney complications in adults with normal blood pressure and microalbuminuria. We are unsure if ACEI compared to vitamin C has any effect on preventing or reducing kidney complications in children with normal blood pressure and microalbuminuria. No RCTs assessed red blood cell transfusions or any combined interventions to prevent or reduce kidney complications. Due to lack of evidence, we cannot comment on the management of children aged over 18 months or adults with any known genotype of SCD. We have identified a lack of adequately designed and powered studies, although we found four ongoing trials since the last version of this review. Only one ongoing trial addresses renal function as a primary outcome in the short term, but such interventions have long-term effects. Trials of hydroxyurea, ACEIs or red blood cell transfusion in older children and adults are urgently needed to determine any effect on prevention or reduction of kidney complications in people with SCD.

Blockade of the mineralocorticoid receptor improves markers of human endothelial cell dysfunction and hematological indices in a mouse model of sickle cell disease

Increased endothelin-1 (ET-1) levels in patients with sickle cell disease (SCD) and transgenic mouse models of SCD contribute to disordered hematological, vascular, and inflammatory responses. Mineralocorticoid receptor (MR) activation by aldosterone, a critical component of the Renin-Angiotensin-Aldosterone-System, modulates inflammation and vascular reactivity, partly through increased ET-1 expression. However, the role of MR in SCD remains unclear. We hypothesized that MR blockade in transgenic SCD mice would reduce ET-1 levels, improve hematological parameters, and reduce inflammation. Berkeley SCD (BERK) mice, a model of severe SCD, were randomized to either sickle standard chow or chow containing the MR antagonist (MRA), eplerenone (156 mg/Kg), for 14 days. We found that MRA treatment reduced ET-1 plasma levels (p = .04), improved red cell density gradient profile (D50 ; p < .002), and increased mean corpuscular volume in both erythrocytes (p < .02) and reticulocytes (p < .024). MRA treatment also reduced the activity of the erythroid intermediate-conductance Ca2+ -activated K+ channel - KCa 3.1 (Gardos channel, KCNN4), reduced cardiac levels of mRNAs encoding ET-1, Tumor Necrosis Factor Receptor-1, and protein disulfide isomerase (PDI) (p < .01), and decreased plasma PDI and myeloperoxidase activity. Aldosterone (10-8  M for 24 h in vitro) also increased PDI mRNA levels (p < .01) and activity (p < .003) in EA.hy926 human endothelial cells, in a manner blocked by pre-incubation with the MRA canrenoic acid (1 μM; p < .001). Our results suggest a novel role for MR activation in SCD that may exacerbate SCD pathophysiology and clinical complications.

Emerging Therapies and Advances in Sickle Cell Disease with a Focus on Renal Manifestations

The underlying mechanisms of disease in sickle cell disease (SCD) contribute to a multifaceted nephropathy, commonly manifested as albuminuria. In severe SCD genotypes ( e.g. , Hemoglobin SS [HbSS]), albuminuria and CKD are major predictors of mortality in this population. Therefore, the monitoring and management of renal function is an intrinsic part of comprehensive care in SCD. Management of nephropathy in SCD can be accomplished with SCD-directed therapies and/or CKD-directed therapies. In the past 5 years, novel disease-modifying and palliative therapies have been approved in SCD to target aspects of the disease, such as anemia, inflammation, and vasculopathy. Along with conventional hydroxyurea and chronic transfusion, l -glutamine, crizanlizumab, and voxelotor have all been shown to mitigate some adverse effect of SCD, and their effect on nephropathy is being investigated. CKD-directed therapies such as renin-angiotensin-aldosterone system blockers have long been used in SCD nephropathy; however, more complete long-term studies on benefits are needed. Given the effect of renal disease on survival, further assessment of the mechanisms and efficacy of these SCD-directed or CKD-directed therapeutic agents is essential.

Factors influencing blood pressure fluctuation in pediatric patients with sickle cell disease in Saudi Arabia: A retrospective single-center cohort study

OBJECTIVES

To investigate changes in blood pressure (BP) among pediatric patients with sickle cell disease (SCD) and determine the variables that might influence these changes.

METHODS

A total of 100 pediatric patients with SCD who followed up in the pediatric outpatient clinic were recruited for this retrospective cohort study. Clinical data included anthropometric measures, average systolic and diastolic BP recorded during multiple follow-up visits, hemoglobin (Hb) level, serum creatinine, and hemoglobin S percentage. Blood pressure measurements were categorized according to the guidelines of the American Academy of Pediatrics (AAP, 2017).

RESULTS

In this cohort, 68% of the patients had normal systolic BP, 13% had elevated systolic BP, 17% had stage 1 hypertension (HTN), while only 2% reported stage 2 HTN. Patients who were overweight had relatively high systolic BP compared to patients who were underweight (p=0.034) or had normal weight (p=0.023). The average systolic BP significantly correlates with body mass index (r= 0.377, p<0.001) and serum creatinine (r=0.369, p<0.001).

CONCLUSION

Pediatric overweight SCD patients exhibited higher average systolic BP than those underweight or normal weight. Body mass index and serum creatinine significantly influenced the average systolic BP more than the Hb level or Hb S percentage.

Induction of Hepcidin Expression in the Renal Cortex of Sickle Cell Disease Mice

In patients with sickle cell disease (SCD), chronic hemolysis and frequent blood transfusions cause iron overload and accumulation in the kidneys. The iron deposition is found in the renal cortex and correlates with the severity of hemolysis. In this study, we observed a significant accumulation of iron in the renal cortex of a mouse model of SCD, and assessed the expression of the proteins involved in maintaining renal iron homeostasis. Despite the intracellular iron accumulation, the levels of the transferrin receptor in the kidneys were increased, but the levels of the iron exporter ferroportin were not altered in SCD mice. Ferroportin is regulated by hepcidin, which binds to it and promotes its degradation. We found reduced serum hepcidin levels but increased renal hepcidin production in SCD mice. Furthermore, we observed significant macrophage infiltration and increased expression of intercellular adhesion molecule 1 in the endothelial cells of the kidneys in SCD mice. These observations correlated with elevated levels of proinflammatory cytokines IL-1β and IL-6, which can potentially stimulate hepcidin expression. Taken together, our results demonstrate that in individuals with SCD, a renal inflammation state induces renal hepcidin production that blocks the upregulation of ferroportin levels, resulting in dysregulation of iron homeostasis in the kidney and iron deposition in the renal cortex.

Multi-Organ Morphological Findings in a Humanized Murine Model of Sickle Cell Trait

Sickle cell disease (SCD) is caused by the homozygous beta-globin gene mutation that can lead to ischemic multi-organ damage and consequently reduce life expectancy. On the other hand, sickle cell trait (SCT), the heterozygous beta-globin gene mutation, is still considered a benign condition. Although the mechanisms are not well understood, clinical evidence has recently shown that specific pathological symptoms can also be recognized in SCT carriers. So far, there are still scant data regarding the morphological modifications referable to possible multi-organ damage in the SCT condition. Therefore, after genotypic and hematological characterization, by conventional light microscopy and transmission electron microscopy (TEM), we investigated the presence of tissue alterations in 13 heterozygous Townes mice, one of the best-known animal models that, up to now, was used only for the study of the homozygous condition. We found that endothelial alterations, as among which the thickening of vessel basal lamina, are ubiquitous in the lung, liver, kidney, and spleen of SCT carrier mice. The lung shows the most significant alterations, with a distortion of the general tissue architecture, while the heart is the least affected. Collectively, our findings contribute novel data to the histopathological modifications at microscopic and ultrastructural levels, underlying the heterozygous beta-globin gene mutation, and indicate the translational suitability of the Townes model to characterize the features of multiple organ involvement in the SCT carriers.

Urinary angiotensinogen is associated with albuminuria in adults with sickle cell anaemia

We explored the association of novel urinary biomarkers with albumin-creatinine ratio (ACR) in adults with sickle cell anaemia. Of 37 participants, 13 (35.2%) had persistent albuminuria (PA). Urinary levels of clusterin (p = 0.002), retinol-binding protein 4 (p = 0.008), alpha-1 microglobulin (p = 0.002) and angiotensinogen (p = 0.006) were significantly higher in participants with PA than in those without PA. Although univariate analysis showed significant associations between both alpha-1 microglobulin (p = 0.035) and angiotensinogen (p = 0.0021) with ACR, only angiotensinogen was associated with ACR in multivariable analysis (p = 0.04). Our results suggest that urinary angiotensinogen may identify sickle cell anaemia patients at risk for kidney disease.

Pathophysiological characterization of the Townes mouse model for sickle cell disease

A deeper pathophysiologic understanding of available mouse models of sickle cell disease (SCD), such as the Townes model, will help improve preclinical studies. We evaluated groups of Townes mice expressing either normal adult human hemoglobin (HbA), sickle cell trait (HbAS), or SCD (HbS), comparing younger versus older adults, and females versus males. We obtained hematologic parameters in steady-state and hypoxic conditions and evaluated metabolic markers and cytokines from serum. Kidney function was evaluated by measuring the urine protein/creatinine ratio and urine osmolality. In vivo studies included von Frey assay, non-invasive plethysmography, and echocardiography. Histopathological evaluations were performed in lung, liver, spleen, and kidney tissues. HbS mice displayed elevated hemolysis markers and white blood cell counts, with some increases more pronounced in older adults. After extended in vivo hypoxia, hemoglobin, platelet counts, and white blood cell counts decreased significantly in HbS mice, whereas they remained stable in HbA mice. Cytokine analyses showed increased TNF-alpha in HbS mice. Kidney function assays revealed worsened kidney function in HbS mice. The von Frey assay showed a lower threshold to response in the HbS mice than controls, with more noticeable differences in males. Echocardiography in HbS mice suggested left ventricular hypertrophy and dilatation. Plethysmography suggested obstructive lung disease and inflammatory changes in HbS mice. Histopathological studies showed vascular congestion, increased iron deposition, and disruption of normal tissue architecture in HbS mice. These data correlate with clinical manifestations in SCD patients and highlight analyses and groups to be included in preclinical therapeutic studies.

Estimated glomerular filtration rate in Brazilian adults with sickle cell disease: results from the REDS-III multicenter cohort study

Chronic kidney disease (CKD) has a significant impact on sickle cell disease (SCD) morbidity and mortality. Early identification of individuals at highest risk of developing CKD may allow therapeutic intervention to prevent worse outcomes. This study aimed to evaluate the prevalence and risk factors for reduced estimated glomerular filtration rate (eGFR) among adults with SCD in Brazil. Participants in the REDS-III multicenter SCD cohort with more severe genotypes aged ≥ 18 years with at least two serum creatinine values were analyzed. The eGFR was calculated using the Jamaica Sickle Cell Cohort Study GFR equation. The eGFR categories were defined according to the K/DOQI. Participants with eGFR ≥ 90 were compared to those with those with eGFR < 90. Among the 870 participants, 647 (74.4%) had eGFR ≥ 90, 211 (24.3%) had eGFR 60 to 89, six (0.7%) had eGFR 30 to 59, and six (0.7%) had ESRD. Male sex (OR: 37.3; 95%CI: 22.4-65.1), higher age (OR: 1.04; 95%CI: 1.02-1.06), higher diastolic blood pressure (OR: 1.03; 95%CI: 1.009-1.06), lower Hb (OR: 0.80; 95%CI: 0.68-0.93), and lower reticulocytes (OR: 0.94; 95%CI: 0.89-0.99) levels were independently associated with eGFR < 90. There was a trend towards higher odds of death in participants with eGFR < 90 (OR: 1.8; 95%CI: 0.95-3.32; p = 0.065). In turn, participants with eGFR < 60 had a 12.2 (95%CI: 2.1-96.9) times higher odds for death when compared to those with eGFR ≥ 60. In this study, eGFR < 90 was observed in one-quarter of adults. Older age, male sex, higher diastolic blood pressure, lower hemoglobin, and lower reticulocyte levels were associated with occurrence of eGFR < 90. Estimated GFR < 60 increased the risk of mortality.

Epidemiology and Outcomes of Glomerular Diseases in Low- and Middle-Income Countries

Glomerular diseases account for a significant proportion of chronic kidney disease in low-income and middle-income countries (LMICs). The epidemiology of glomerulonephritis is characterized inadequately in LMICs, largely owing to unavailable nephropathology services or uncertainty of the safety of the kidney biopsy procedure. In contrast to high-income countries where IgA nephropathy is the dominant primary glomerular disease, focal segmental glomerulosclerosis is common in large populations across Latin America, Africa, Middle East, and South East Asia, while IgA nephropathy is common in Chinese populations. Despite having a high prevalence of known genetic and viral risk factors that trigger focal segmental glomerulosclerosis, membranoproliferative glomerulonephritis also is common in adults and children in some African countries. Treatment of glomerular diseases in adults and children in LMICs largely is dependent on corticosteroids in combination with other immunosuppressive therapy, which often is cyclophosphamide because of its ready availability and low cost of treatment, despite significant adverse effects. Partial and/or complete remission status reported from studies of glomerular disease subtypes vary across LMIC regions, with high rates of kidney failure, mortality, and disease, and treatment complications often reported. Improving the availability of nephropathology services and ensuring availability of specific therapies are key measures to improving glomerular disease outcomes in LMICs.

Glomerular filtration rate abnormalities in sickle cell disease

Sickle cell disease (SCD) is a group of inherited blood disorders affecting the β-globin gene, resulting in the polymerization of hemoglobin and subsequent sickling of the red blood cell. Renal disease, the most common complication in SCD, begins in childhood with glomerular hyperfiltration and then progresses into albuminuria, a fast decline of glomerular filtration, and renal failure in adults. This mini-review focuses on glomerular filtration abnormalities and the mechanisms of hyperfiltration, explores genetic modifiers and methods of estimating glomerular filtration rates, and examines novel biomarkers of glomerular filtration in SCD.

ATR1 Angiotensin II Receptor Reduces Hemoglobin S Polymerization, Phosphatidylserine Exposure, and Increases Deformability of Sickle Cell Disease Erythrocytes

Angiotensin II (Ang II) regulates blood volume and stimulates erythropoiesis through AT1 (ATR1) and AT2 (ATR2) receptors, found in multiple tissues, including erythrocytes. Sickle cell disease (SCD) patients present altered Ang II levels. Hemoglobin S polymerization, deformability and phosphatidylserine translocation are important features of mature erythrocytes, therefore, our hypothesis is Ang II affects these parameters and, if it does, what would be the influence of AT1R and AT2R on these effects. A polymerization assay (PA), deformability, and annexin V binding were performed in SCD erythrocytes samples adding Ang II, ATR1 antagonist (losartan or eprosartan), and ATR2 antagonist (PD123319). Through the PA test, we observed a dose-dependent polymerization inhibition effect when comparing Ang II to control. Losartan did not affect the level or the rate of Ang II inhibition, while PD123319 showed an increased level of protection against polymerization, and eprosartan brought levels back to control. Ang II was able to reduce the translocation of phosphatidylserine from the inner to the outer leaflet, a marker of eryptosis, in the presence of PD123319. Also, ATR1 showed a positive effect increasing deformability. Our data shows that ATR1 is important for maintenance of erythrocyte physiological function in SCD and for prolonging its life.

Hypothesis: Low Vitamin A and D Levels Worsen Clinical Outcomes When Children with Sickle Cell Disease Encounter Parvovirus B19

Human parvovirus B19 causes life-threatening anemia due to transient red cell aplasia (TRCA) in individuals with sickle cell disease (SCD). Children with SCD experiencing profound anemia during TRCA often require red blood cell transfusions and hospitalization. The prevalence of vitamin deficiencies in SCD is high and deficiencies are associated with respiratory and pain symptoms, but the effects of vitamins on acute infection with parvovirus B19 remain unclear. We performed a clinical study in which 20 SCD patients hospitalized with parvovirus B19 infections (Day 0) were monitored over a 120-day time course to query relationships between vitamins A and D and clinical outcomes. There were significant negative correlations between Day 0 vitamin levels and disease consequences (e.g., red blood cell transfusion requirements, inflammatory cytokines). There were significant positive correlations (i) between Day 0 vitamins and peak virus-specific antibodies in nasal wash, and (ii) between Day 0 virus-specific serum plus nasal wash antibodies and absolute reticulocyte counts. There was a significant negative correlation between Day 0 virus-specific serum antibodies and virus loads. To explain the results, we propose circular and complex mechanisms. Low baseline vitamin levels may weaken virus-specific immune responses to permit virus amplification and reticulocyte loss; consequent damage may further reduce vitamin levels and virus-specific immunity. While the complex benefits of vitamins are not fully understood, we propose that maintenance of replete vitamin A and D levels in children with SCD will serve as prophylaxis against parvovirus B19-induced TRCA complications.

Longitudinal Study of Glomerular Hyperfiltration in Adults with Sickle Cell Anemia: A Multicenter Pooled Analysis

Glomerular hyperfiltration is common in young sickle cell anemia patients and precedes development of overt kidney disease. In this multicenter pooled cohort, we characterized hyperfiltration and its decline to normal range in adult patients. Glomerular filtration rate (GFR) was estimated using the creatinine-based 2009 CKD-EPI (Chronic Kidney Disease Epidemiology Collaboration) equation omitting race adjustment and the 2021 CKD-EPI equation. Using CKD-EPI–2009, 506 patients had baseline estimated GFR (eGFR) ≥90 mL/min per 1.73 m², median age of 24 (interquartile range [IQR], 19-34) years and 5.17 years of follow-up. The prevalence of hyperfiltration (eGFR ≥140 and ≥130 mL/min per 1.73 m² for men and women, respectively) was 38.3%. Using CKD-EPI–2009, baseline hyperfiltration was less likely with older age (odds ratio [OR], 0.78; 95% confidence interval [CI], 0.73-0.83; P < .0001), male sex (OR, 0.32; 95% CI, 0.18-0.58; P = .0002), and higher weight (OR, 0.96; 95% CI, 0.94-0.99; P = .001). Using CKD-EPI–2021, hyperfiltration was similarly less likely with older age (OR, 0.75; 95% CI, 0.70-0.81; P < .0001), male sex (OR, 0.24; 95% CI, 0.13-0.44; P < .0001), and higher weight (OR, 0.97; 95% CI, 0.95-0.99; P = .004). In patients with baseline hyperfiltration, eGFR declined to normal values at a median age of 26.2 years. Using CKD-EPI–2009, this decline was associated with male sex (HR, 2.20; 95% CI, 1.26-3.87; P = .006), systolic blood pressure (hazard ratio [HR], 1.02; 95% CI, 1.01-1.04; P = .01), and hydroxyurea use (HR, 1.74; 95% CI, 1.002-3.03; P = .05). Using CKD-EPI–2021, decline of eGFR to normal was only associated with male sex (HR, 3.39; 95% CI, 2.01-5.69; P < .0001). Decline to normal eGFR range from hyperfiltration occurs earlier in males, those on hydroxyurea, and with higher systolic blood pressure.

The nephropathy of sickle cell trait and sickle cell disease

Sickle cell syndromes, including sickle cell disease (SCD) and sickle cell trait, are associated with multiple kidney abnormalities. Young patients with SCD have elevated effective renal plasma flow and glomerular filtration rates, which decrease to normal ranges in young adulthood and subnormal levels with advancing age. The pathophysiology of SCD-related nephropathy is multifactorial - oxidative stress, hyperfiltration and glomerular hypertension are all contributing factors. Albuminuria, which is an early clinical manifestation of glomerular damage, is common in individuals with SCD. Kidney function declines more rapidly in individuals with SCD than in those with sickle cell trait or in healthy individuals. Multiple genetic modifiers, including APOL1, HMOX1, HBA1 and HBA2 variants are also implicated in the development and progression of SCD-related nephropathy. Chronic kidney disease and rapid decline in estimated glomerular filtration rate are associated with increased mortality in adults with SCD. Renin-angiotensin-aldosterone system inhibitors are the standard of care treatment for albuminuria in SCD, despite a lack of controlled studies demonstrating their long-term efficacy. Multiple studies of novel therapeutic agents are ongoing, and patients with SCD and kidney failure should be evaluated for kidney transplantation. Given the high prevalence and severe consequences of kidney disease, additional studies are needed to elucidate the pathophysiology, natural history and treatment of SCD-related nephropathy.

Sickle Cell Disease and Kidney

Sickle cell disease causes several kidney manifestations. They include defects in urine concentration, impaired handling of potassium and hydrogen ion, albuminuria, acute kidney injury, and chronic kidney disease to name a few. Glomerular hyperfiltration, tubular hyperfunctioning, endothelial damage from repeated sickling and vaso-occlusive episodes, and iron-induced proinflammatory changes in the glomerular mesangium and tubulointerstitium are some of the mechanisms of kidney damage. Albuminuria is one of the most and common clinical features of kidney disease and progresses with age. Kidney disease in patients with sickle cell is associated with increased mortality. Annual screening for proteinuria starting at age 10 years and limiting the use of nonsteroidal anti-inflammatory agents and the use of angiotensin-converting enzyme inhibitors may help in early detection and delaying the progression of kidney disease. Adequate hydration, angiotensin-converting enzyme inhibitors, and adequate control of sickle cell are the main stay of treatment for albuminuria. The hemoglobin goal for patients with sickle cell nephropathy is lesser (10 g/dL) than that for patients with chronic kidney disease due to other causes given that a higher hemoglobin level increases viscosity and the risk of precipitating vaso-occlusive episodes. A multidisciplinary approach is recommended for managing patients with sickle cell and kidney diseases.

The pharmacokinetic and safety profile of single-dose deferiprone in subjects with sickle cell disease

Patients with sickle cell disease (SCD) who undergo repeated blood transfusions often develop iron overload. Deferiprone (Ferriprox®) is an oral iron chelator indicated for the treatment of transfusional iron overload due to thalassemia syndromes and has been recently approved as a treatment for iron overload in adult and pediatric patients with SCD and other anemias. The present study aims to characterize the pharmacokinetic (PK) profile of deferiprone (DFP) in adult subjects with SCD. In this phase I, open-label study, subjects with SCD were administered a single 1500 mg dose of DFP. Blood and urine samples were collected for PK assessments of DFP and its main metabolite, deferiprone 3-O-glucuronide (DFP-G). Eight subjects were enrolled and completed the study. Following drug administration, serum levels of DFP and DFP-G rose to maximum concentrations at 1.0 and 2.8 h post-dose, respectively. The half-lives of DFP and DFP-G were 1.5 and 1.6 h, respectively. The majority of administered drug was metabolized and excreted as DFP-G, with less than 4% excreted unchanged in urine up to 10 h post-dose. Subjects received a safety assessment 7 (± 3) days post-dose. Two subjects reported mild adverse events unrelated to the study drug, and no other safety concerns were reported. The PK profile of DFP in SCD subjects is consistent with previous reports in healthy adult volunteers, suggesting no special dosing adjustments are indicated for this population. These findings provide valuable insight for treating iron overload in patients with SCD, who have limited chelation therapy treatment options (trial registration number: NCT01835496, date of registration: April 19, 2013).

Clinical and genetic factors are associated with kidney complications in African children with sickle cell anaemia

Clinical and genetic factors have been reported as influencing the development of sickle cell nephropathy (SCN). However, such data remain limited in the paediatric population. In this cross-sectional study, we enrolled 361 sickle cell disease children from the Democratic Republic of Congo. Participants were genotyped for the beta (β)-globin gene, apolipoprotein L1 (APOL1) risk variants, and haem oxygenase-1 (HMOX1) GT-dinucleotide repeats. As markers of kidney damage, albuminuria, hyperfiltration and decreased estimated glomerular filtration with creatinine (eGFRcr) were measured. An association of independent clinical and genetic factors with these markers of kidney damage were assessed via regression analysis. Genetic sequencing confirmed sickle cell anaemia in 326 participants. Albuminuria, hyperfiltration and decreased eGFRcr were present in 65 (20%), 52 (16%) and 18 (5·5%) patients, respectively. Regression analysis revealed frequent blood transfusions, indirect bilirubin and male gender as clinical predictors of SCN. APOL1 high-risk genotype (G1/G1, G2/G2 and G1/G2) was significantly associated with albuminuria (P = 0·04) and hyperfiltration (P = 0·001). HMOX1 GT-dinucleotide long repeats were significantly associated with lower eGFRcr. The study revealed a high burden of kidney damage among Congolese children and provided evidence of the possible role of APOL1 and HMOX1 in making children more susceptible to kidney complications.

Longitudinal study of glomerular hyperfiltration and normalization of estimated glomerular filtration in adults with sickle cell disease

Glomerular hyperfiltration is common in sickle cell disease (SCD) and precedes proteinuria and declining kidney function. We evaluated hyperfiltration in SCD patients and its "normalization." Routine visit data were collected retrospectively from adult SCD patients in a single centre from 2004 to 2013. Baseline was defined as first available serum creatinine and hyperfiltration as estimated glomerular filtration rates (eGFR) >130 ml/min/1·73 m² for women and >140 ml/min/1·73 m² for men. Normalization of hyperfiltration was eGFR reduction to 90-130 ml/min/1·73 m² for women or 90-140 ml/min/1·73 m² for men. Among 292 patients, median age was 27 years [interquartile range (IQR):20·0-38·0], and 56·8% had baseline hyperfiltration. Baseline hyperfiltration was inversely associated with age [odds ratio (OR):0·86, 95% confidence interval (CI): 0·82-0·90; P < 0·0001], male sex (OR:0·16, 95% CI: 0·07-0·41; P = 0·0001), haemoglobin (OR:0·76, 95% CI 0·61-0·94; P = 0·01), weight (OR:0·96, 95% CI: 0·93-0·99; P = 0·004), and angiotensin-converting enzyme inhibitor/angiotensin receptor blocker (ACE-I/ARB) use (OR:0·08, 95% CI: 0·01-0·75; P = 0·03), and positively with hydroxycarbamide use (OR:2·99, 95% CI: 1·18-7·56; P = 0·02). Of 89 hyperfiltration patients without baseline proteinuria, 10 (11·2%) developed new-onset proteinuria [median 1·05 years (IQR:0·63-2·09)]. Normalization of hyperfiltration was less likely with higher baseline eGFR [hazard ratio (HR):0·90, 95% CI: 0·86-0·95; P < 0·0001] and more likely in males (HR:6·35, 95% CI:2·71-14·86, <0·0001). Hyperfiltration is common in adult SCD patients, particularly when younger. Decline to normal values is more likely in males, possibly representing kidney function loss rather than improvement in hyperfiltration.

Gabapentin for acute pain in sickle cell disease: A randomized double-blinded placebo-controlled phase II clinical trial

Pain in sickle cell disease (SCD) can have a neuropathic component. This randomized phase II double-blinded placebo-controlled study evaluated the efficacy of gabapentin in reducing pain and opioid consumption (morphine-equivalent dose [MED]) during acute vaso-occlusive crisis (VOC). Of 90 patients aged 1-18 years with VOC pain, 45 were randomized to a single gabapentin dose (15 mg/kg) and 45 to placebo, in addition to standard treatment; 42 and 44 patients were evaluable in the gabapentin and placebo arms, respectively. A decrease in pain of ≥33% was reported in 68% of patients in the gabapentin arm and 60% of those in the placebo arm (one-sided p = 0.23). The median MED (mg/kg) in the gabapentin (0.12) and placebo arms (0.13) was similar (p = 0.9). However, in the subset of patients with the HbSS genotype (n = 45), the mean (SD) absolute pain score decrease by the time of discharge was significantly greater in the gabapentin arm (5.9 [3.5]) than in the placebo arm (3.6 [3.3]) (p = 0.032). Pain scores in the overall study population were not significantly reduced when gabapentin was added to standard treatment; however, gabapentin benefited individuals with the more severe genotype, HbSS, during acute VOC. Larger, prospective studies are needed to confirm these findings.

Sickle cell nephropathy. Clinical manifestations and new mechanisms involved in kidney injury

Kidney problems are among the most common complications in sickle cell disease (SCD). They occur early in childhood and are one of the main factors related to mortality in these patients. The main underlying pathogenic mechanisms are vaso-occlusion and haemolysis. The renal medulla has ideal conditions for the sickling of red cells due to its low partial pressure of oxygen, high osmolarity and acidic pH. Initially, sickle-cell formation in the vasa recta of the renal medulla causes hyposthenuria. This is universal and appears in early childhood. Microscopic and macroscopic haematuria also occur, in part related to renal papillary necrosis when the infarcts are extensive. Release of prostaglandins in the renal medulla due to ischaemia leads to an increase in the glomerular filtration rate (GFR). Adaptively, sodium reabsorption in the proximal tubule increases, accompanied by increased creatinine secretion. Therefore, the GFR estimated from creatinine may be overestimated. Focal segmental glomerulosclerosis is the most common glomerular disease. Albuminuria is very common and reduction has been found in 72.8% of subjects treated with ACE inhibitors or ARB. Recent evidence suggests that free haemoglobin has harmful effects on podocytes, and may be a mechanism involved in impaired kidney function in these patients. These effects need to be better studied in SCD, as they could provide a therapeutic alternative in sickle cell nephropathy.

Generalization of a genetic risk score for time to first albuminuria in children with sickle cell anaemia: SCCRIP cohort study results

Albuminuria predicts kidney disease progression in individuals with sickle cell anaemia (SCA); however, earlier prediction of kidney disease with introduction of reno-protective therapies prior to the onset of albuminuria may attenuate disease progression. A genetic risk score (GRS) for SCA-related nephropathy may provide an improved one-time test for early identification of high-risk patients. We utilized a GRS from a recent, large, trans-ethnic meta-analysis to identify three single nucleotide polymorphisms that associate individually and in a GRS with time to first albuminuria episode in children with SCA.

Rapid decline in estimated glomerular filtration rate in sickle cell anemia: results of a multicenter pooled analysis

Not available.

Progression of albuminuria in patients with sickle cell anemia: a multicenter, longitudinal study

Sickle cell nephropathy results in chronic kidney disease (CKD), which is associated with significant morbidity and mortality in sickle cell anemia (SCA). Albuminuria is an early manifestation of sickle nephropathy; however, little is known about progression of albuminuria or its correlation with glomerular filtration rate (GFR) decline or CKD. We studied nephropathy progression in 303 SCA participants in a prospective, multicenter, longitudinal study. We collected steady-state urine and serum samples yearly and assessed albumin/creatinine ratio (ACR), estimated GFR (eGFR), and SCA and nephropathy biomarkers. Participants with albuminuria (ACR ≥30 mg/g) for ≥2 annual measurements were classified as having persistent albuminuria (PA). At baseline (mean age, 21 years; range, 2-64 years), 32% had albuminuria. In longitudinal multivariate analysis, ACR was associated with sex, anemia, older age, and higher bilirubin and kidney injury molecule-1 levels. Albuminuria increased with age by 3.5 mg/g per year (P < .0001). Of 175 participants with ≥3 annual samples, 81% with baseline albuminuria ≥100 mg/g developed PA. Decreased eGFR and adult CKD were associated with PA (P = .002 and P = .02, respectively), but not with baseline albuminuria. Rate of eGFR decline was steeper among adults (but not children) with albuminuria, compared with those without (P = .02). Participants with PA were more likely to have rapid eGFR decline compared with those without (P = .03). In this longitudinal study, albuminuria progressed with age, and adults with albuminuria had worse eGFR decline than those without. Albuminuria ≥100 mg/g predicted PA, which was associated with rapid eGFR decline and CKD development in adults with SCA. This trial was registered at www.clinicaltrials.gov as #NCT02239016.

Investigations of Kidney Dysfunction-Related Gene Variants in Sickle Cell Disease Patients in Cameroon (Sub-Saharan Africa)

Background

Renal dysfunctions are associated with increased morbidity and mortality in sickle cell disease (SCD). Early detection and subsequent management of SCD patients at risk for renal failure and dysfunctions are essential, however, predictors that can identify patients at risk of developing renal dysfunction are not fully understood.

Methods

In this study, we have investigated the association of 31 known kidney dysfunctions-related variants detected in African Americans from multi-ethnic genome wide studies (GWAS) meta-analysis, to kidney-dysfunctions in a group of 413 Cameroonian patients with SCD. Systems level bioinformatics analyses were performed, employing protein-protein interaction networks to further interrogate the putative associations.

Results

Up to 61% of these patients had micro-albuminuria, 2.4% proteinuria, 71% glomerular hyperfiltration, and 5.9% had renal failure. Six variants are significantly associated with the two quantifiable phenotypes of kidney dysfunction (eGFR and crude-albuminuria): A1CF-rs10994860 (P = 0.02020), SYPL2-rs12136063 (P = 0.04208), and APOL1 (G1)-rs73885319 (P = 0.04610) are associated with eGFR; and WNT7A-rs6795744 (P = 0.03730), TMEM60-rs6465825 (P = 0.02340), and APOL1 (G2)-rs71785313 (P = 0.03803) observed to be protective against micro-albuminuria. We identified a protein-protein interaction sub-network containing three of these gene variants: APOL1, SYPL2, and WNT7A, connected to the Nuclear factor NF-kappa-B p105 subunit (NFKB1), revealed to be essential and might indirectly influence extreme phenotypes. Interestingly, clinical variables, including body mass index (BMI), systolic blood pressure, vaso-occlusive crisis (VOC), and haemoglobin (Hb), explain better the kidney phenotypic variations in this SCD population.

Conclusion

This study highlights a strong contribution of haematological indices (Hb level), anthropometric variables (BMI, blood pressure), and clinical events (i.e., vaso-occlusive crisis) to kidney dysfunctions in SCD, rather than known genetic factors. Only 6/31 characterised gene-variants are associated with kidney dysfunction phenotypes in SCD samples from Cameroon. The data reveal and emphasise the urgent need to extend GWAS studies in populations of African ancestries living in Africa, and particularly for kidney dysfunctions in SCD.

Sickle cell nephropathy. Clinical manifestations and new mechanisms involved in kidney injury

Kidney problems are among the most common complications in sickle cell disease (SCD). They occur early in childhood and are one of the main factors related to mortality in these patients. The main underlying pathogenic mechanisms are vaso-occlusion and haemolysis. The renal medulla has ideal conditions for the sickling of red cells due to its low partial pressure of oxygen, high osmolarity and acidic pH. Initially, sickle-cell formation in the vasa recta of the renal medulla causes hyposthenuria. This is universal and appears in early childhood. Microscopic and macroscopic haematuria also occur, in part related to renal papillary necrosis when the infarcts are extensive. Release of prostaglandins in the renal medulla due to ischaemia leads to an increase in the glomerular filtration rate (GFR). Adaptively, sodium reabsorption in the proximal tubule increases, accompanied by increased creatinine secretion. Therefore, the GFR estimated from creatinine may be overestimated. Focal segmental glomerulosclerosis is the most common glomerular disease. Albuminuria is very common and reduction has been found in 72.8% of subjects treated with ACE inhibitors or ARB. Recent evidence suggests that free haemoglobin has harmful effects on podocytes, and may be a mechanism involved in impaired kidney function in these patients. These effects need to be better studied in SCD, as they could provide a therapeutic alternative in sickle cell nephropathy.

Nephrotic syndrome on sickle cell disease: the impact of Hydroxyurea

Nephropathy is a common under-recognised complication of sickle cell disease (SCD) and one of the main factors of poor prognosis in these patients. The association between nephrotic syndrome and SCD in children is rare. Strategies for sickle cell nephropathy prevention are still poorly established. Blood pressure control as well as monitoring of microalbuminuria and renal function are mandatory. The use of antiproteinuric drugs, such as anti-ACE inhibitors (ACEis) and hydroxyurea, should be considered in early stages. Here, we report a case of a female adolescent with SCD and inaugural nephrotic syndrome who, after an initial treatment failure with corticotherapy, had a remarkable recovery after treatment with hydroxyurea and ACEis.

Mortality and Hospitalizations among Sickle Cell Disease Patients with End-Stage Kidney Disease Initiating Dialysis

BACKGROUND

Sickle cell disease (SCD) is the most common inherited hematological disorder and a well-described risk factor for end-stage kidney disease (ESKD). Mortality and hospitalizations among patients with SCD who develop ESKD remain understudied. Furthermore, prior studies focused only on SCD patients where ESKD was caused by SCD. We aimed to describe mortality and hospitalization risk in all SCD patients initiating dialysis and explore risk factors for mortality and hospitalization.

METHODS

We performed a national observational cohort study of African American ESKD patients initiating dialysis (2000-2014) in facilities affiliated with a large dialysis provider. SCD was identified by diagnosis codes and matched to a reference population (non-SCD) by age, sex, dialysis initiation year, and geographic region of care. Sensitivity analyses were conducted by restricting to patients where SCD was recorded as the cause of ESKD.

RESULTS

We identified 504 SCD patients (mean age: 47 ± 14 years; 48% females) and 1,425 reference patients (mean age: 46 ± 14 years; 49% females). The median follow-up was 2.4 (IQR 1.0-4.5) years. Compared to the reference, SCD was associated with higher mortality risk (hazard ratio 1.66; 95% confidence interval [CI]: 1.36-2.03) and higher hospitalization rates (incidence rate ratio 2.12; 95% CI: 1.88-2.38) in multivariable analyses. Exploratory multivariable mortality risk models showed the largest mortality risk attenuation with the addition of time-varying hemoglobin and high-dose erythropoietin, but the association of SCD with mortality remained significant. Sensitivity analyses (restricted to ESKD caused by SCD) also showed significant associations between SCD and mortality and hospitalizations, but with larger effect estimates. High-dose erythropoietin was associated with the highest risk for mortality and hospitalization in SCD.

CONCLUSIONS

Among ESKD patients, SCD is associated with a higher risk for mortality and hospitalization, particularly in patients where SCD is identified as the cause of ESKD.

Stable renal function in children and adolescents with sickle cell disease after nonmyeloablative hematopoietic stem cell transplantation

BACKGROUND

Sickle cell disease (SCD) is associated with renal complications starting as early as infancy. Allogeneic hematopoietic stem cell transplant (HSCT) treatments using newer nonmyeloablative (NMA) conditioning regimens show promising results in treating SCD in the pediatric population, but renal outcome parameters after transplantation have not been described.

AIM

To describe baseline renal parameters as well as short- and long-term renal outcomes in pediatric patients with SCD who underwent NMA-HSCT.

METHODS

A retrospective chart review of pediatric patients who received NMA-HSCT in Alberta, Canada. Short-term renal outcomes evaluated were: (1) acute kidney injury (AKI), (2) fluid overload (FO), and (3) hypertension. Long-term outcomes evaluated were: (1) estimated glomerular filtration rate (eGFR) development and at last follow-up with hyperfiltration defined as eGFR ≥ 150 mL/min/1.73 m² , (2) proteinuria, and (3) hypertension.

RESULTS

The mean follow-up time was 128.6 weeks (standard deviations, 69.3). No posttransplant AKI events or FO were observed. eGFR remained > 90 mL/min/1.73 m² at last follow-up in all patients, whereas hyperfiltration was present in eight (44.4%) and four (22.2%) patients pre- and post-HSCT, respectively, which are significantly different (P < 0.0001). Consequently, median GFR was significantly higher pre-HSCT compared with 24 months HSCT (P < 0.009). Long-term hypertension post-HSCT was present in six patients (33.3%).

CONCLUSION

This study describes stable kidney function in children with SCD after NMA-HSCT without evidence of AKI or FO episodes. Rates of hyperfiltration decreased post-HSCT, which signifies that NMA-HSCT could potentially preserve long-term renal function in this population at risk of progressive chronic kidney disease. Further prospective studies are needed to confirm these novel findings.

Atypical presentation of acute post-infectious glomerulonephritis in patients with sickle cell disease: report of two cases

BACKGROUND

Sickle cell disease (SCD) is a highly prevalent genetic disease worldwide. In the natural evolution of SCD, glomerular lesions can develop, presenting histopathological patterns of segmental or focal membranoproliferative glomerulosclerosis, with or without thrombotic microangiopathy. We report two cases of acute post-infectious glomerulonephritis (APIGN), with atypical presentations, in patients with SCD.

CASE PRESENTATION

Case 1: An 18-year-old female with SCD presented with a 21-day history of progressive oedema, accompanied by dyspnoea, productive cough, fever, and chest pain. Blood tests showed the following: haemoglobin 6.1 g/dl; leucocytes 18,820 cells/mm³; and creatinine 0.49 mg/dl. A urine sample evidenced leucocyturia and haematuria. The 24-h proteinuria was 8.99 g, serum albumin level was 1.2 g/dl, low serum C3 levels and high levels of anti-streptolysin O. Renal biopsy was consistent with APIGN. The patient was treated with diuretic and anti-proteinuric agents, subsequently evolving to reversal of the renal alterations. Case 2: A 12-year-old male with SCD presented with a 20-day history of a non-productive cough and progressive oedema, together with hypertension. The serum creatinine concentration was 0.48 mg/dl. A urine sample evidenced leukocyturia and haematuria. The 24-h proteinuria was 12.5 g, and the serum albumin level was 2.6 g/dl. The levels of C3 and C4 were normal. Renal biopsy revealed APIGN. The patient was treated with diuretic and anti-proteinuric agents, subsequently evolving reversal of the renal alterations.

CONCLUSIONS

The presentation of the two cases reported here are not typical of SCD-related kidney injury. Analysis of the renal biopsy specimens elucidated the diagnosis, affecting the prognosis, because that of APIGN is highly favourable, unlike that of nephrotic syndrome associated with SCD glomerulopathy.

The detection of anti-dengue virus IgM in urine in participants enrolled in an acute febrile illness study in Puerto Rico

BACKGROUND

Dengue is an important arboviral disease with about 100 million dengue cases per year, of which, ~5% result in severe disease. Clinical differentiation of dengue from other acute febrile illnesses (AFI) is difficult, and diagnostic blood tests are costly. We evaluated the utility of anti-DENV IgM in urine to identify dengue cases among AFI patients enrolled in a clinical study.

METHODS

Between May 2012-March 2013, 1538 study participants with fever for ≤7 days were enrolled, a medical history was obtained, and serum and urine specimens were collected. Serum was tested for DENV RNA and anti-DENV IgM. Urine was tested for anti-DENV IgM, and its sensitivity and specificity to detect sera laboratory-positive dengue cases were calculated. We evaluated if urine anti-DENV IgM positivity early (≤5 days post-illness onset [DPO]) and late (6-14 DPO) in the clinical course was associated with dengue severity.

RESULTS

Urine anti-DENV IgM sensitivity and specificity were 47.4% and 98.5%, respectively, when compared with serum anti-DENV IgM ELISA results, and 29.7% and 91.1% when compared with serum rRT-PCR results. There was no correlation between urine anti-DENV IgM positivity and patient sex or pre-existing chronic disease. Early in the clinical course, a significantly higher proportion of those who developed dengue with warning signs had anti-DENV IgM in their urine when compared to those without warning signs (20.4% vs. 4.3%). There was no difference in the proportion with urine anti-DENV IgM positivity between severity groups late in the clinical course.

CONCLUSION

While detection of urine anti-DENV IgM lacked adequate diagnostic sensitivity, it is a highly specific marker for laboratory-positive dengue, and its presence early in the clinical course may distinguish those with more severe disease. Further assessment of urine anti-DENV IgM by DPO is warranted to determine its utility as an early diagnostic (and possibly prognostic) marker for dengue.

Effects of hypoxia-reoxygenation stimuli on renal redox status and nuclear factor erythroid 2-related factor 2 pathway in sickle cell SAD mice

NEW FINDINGS

What is the central question of this study? What are the effects of repeated subclinical vaso-occlusions on nuclear factor erythroid 2 related factor 2 (Nrf2) and oxidative stress balance regulation in the kidney of transgenic SAD mice? What is the main finding and its importance? In response to hypoxia-reoxygenation, nuclear Nrf2 protein expression decreased in the kidney of SAD mice while haem oxygenase transcripts were increased. This suggest that in SAD mice, other transcription factors than Nrf2 could be involved in renal antioxidant gene regulation in response to hypoxia-reoxygenation.

ABSTRACT

Hypoxia-reoxygenation (H/R) stress is known to increase oxidative stress in transgenic sickle mice and can cause organ failure. Here we described the effects of H/R on nuclear factor erythroid 2-related factor 2 (Nrf2) as a putative regulator of redox status in the kidneys of SAD mice investigating Nrf2-regulated antioxidant enzymes. Transgenic SAD mice and healthy C57Bl/6J mice were exposed to 4 h of hypoxia followed by various times of reoxygenation at ambient air (2 or 6 h). Regardless of the conditions (i.e. normoxia or H/R), SAD mice expressed higher renal oxidative stress levels. Nuclear Nrf2 protein expression decreased after 2 h post-hypoxia only in the medulla region of the kidney and only in SAD mice. Simultaneously, haem oxygenase transcripts were affected by H/R stimulus with a significant enhancement after 2 h post-hypoxia. Similarly, hypoxia inducible factor-1α staining increased after 2 h post-hypoxia in SAD mice in both cortex and medulla areas. Our data confirm that the kidneys are organs that are particularly sensitive to H/R stimuli in sickle cell SAD mice. Also, these results suggest an effect of the duration of recovery period (short vs. long) and specific responses according to kidney areas, medulla vs. cortex, on Nrf2 expression in response to H/R stimuli in SAD mice.

Renal abnormalities among children with sickle cell conditions in highly resource-limited setting in Ghana

Sickle cell disease (SCD) is associated with progressive multi-organ failure especially, the brain and kidney and leads to high morbidity and mortality rate. The aim of this study was to determine the prevalence of renal abnormalities among children with SCD. This cross-sectional study recruited 212 sickling positive patients comprising of 96 Hb AS, 48 Hb SC, and 68 Hb SS phenotypes from the Pediatric Unit of Wassa Akropong Government Hospital, Wassa Akropong, Ghana. Early morning urine and venous blood samples were collected from each participant. Urinalysis was conducted and serum urea and creatinine levels were estimated. Estimate glomerular filtration rate (eGFR) was calculated using the Swartz equation. Classification of chronic kidney disease (CKD) was based on 'The Kidney Disease: Improving Global Outcomes (KIDIGO)' criteria. The mean age of the children were 7.90 years. Serum creatinine (p = 0.0310) and urea (p<0.0001) levels were significantly higher among Hb AS participants compared with Hb SS phenotype. The prevalent indicators of renal abnormalities were proteinuria (26.4%), urine granular cast (5.6%) and CKD (39.6%). Proteinuria, urine granular cast and CKD were most prevalent among Hb SS (47.1%, 11.8% and 73.5% respectively) compared with Hb SC (41.7%, 8.3%, and 45.8% respectively) and Hb AS (4.2%, 0.0%, and 14.5%) phenotypes, respectively. Sickle cell conditions were significantly associated with proteinuria (p<0.0001) and CKD (p = 0.0378). Children with Hb SS [aOR = 5.04, 95% CI (2.47-10.3); p<0.0001] and Hb SC [aOR = 3.14 95% CI (1.39-7.01); p = 0.0174] were at increased odds of developing CKD after adjusting for age, BMI and gender. Proteinuria and CKD are associated with sickle cell disease (Hb SC and Hb SS). Renal function should be routinely monitored for children with SCD.

Why, Who, When, and How? Rationale for Considering Allogeneic Stem Cell Transplantation in Children with Sickle Cell Disease

Considering the progress made in the management of sickle cell disease during the past 30 years, along with the excellent results obtained with hematopoietic stem cell transplantation (SCT), it is important to reexamine why, who, when and how to recommend allogeneic SCT in children with sickle cell disease. While sickle cell disease has a low risk of death in children and a high risk for morbidity during aging, SCT carries an early risk of death, graft-vs-host disease and infertility. Nevertheless, SCT offers at least 95% chance of cure with low risk of chronic graft-vs-host disease when a matched-sibling donor is available and the risks of infertility can be reduced by ovarian, sperm or testis cryopreservation. Thus, all available therapies such as hydroxyurea, transfusions and SCT should be presented to the parents, providers, and affected children and discussed with them from infancy. Furthermore, the use of these therapies should be adjusted to the severity of the disease and to local availabilities in order to choose the treatment offering the best benefit/risk ratio.

Kidney biopsy findings in children with sickle cell disease: a Midwest Pediatric Nephrology Consortium study

BACKGROUND

Renal damage is a progressive complication of sickle cell disease (SCD). Microalbuminuria is common in children with SCD, while a smaller number of children have more severe renal manifestations necessitating kidney biopsy. There is limited information on renal biopsy findings in children with SCD and subsequent management and outcome.

METHODS

This is a multicenter retrospective analysis of renal biopsy findings and clinical outcomes in children and adolescents with SCD. We included children and adolescents (age ≤ 20 years) with SCD who had a kidney biopsy performed at a pediatric nephrology unit. The clinical indication for biopsy, biopsy findings, subsequent treatments, and outcomes were analyzed.

RESULTS

Thirty-six SCD patients (ages 4-19 years) were identified from 14 centers with a median follow-up of 2.6 years (0.4-10.4 years). The indications for biopsy were proteinuria (92%) and elevated creatinine (30%). All biopsies had abnormal findings, including mesangial hypercellularity (75%), focal segmental glomerulosclerosis (30%), membranoproliferative glomerulonephritis (16%), and thrombotic microangiopathy (2%). There was increased use of hydroxyurea, angiotensin-converting-enzyme inhibitors, and angiotensin receptor blockers following renal biopsy. At last follow-up, 3 patients were deceased, 2 developed insulin-dependent diabetes mellitus, 6 initiated chronic hemodialysis, 1 received a bone marrow transplant, and 1 received a kidney transplant.

CONCLUSIONS

Renal biopsies, while not commonly performed in children with SCD, were universally abnormal. Outcomes were poor in this cohort of patients despite a variety of post-biopsy interventions. Effective early intervention to prevent chronic kidney disease (CKD) is needed to reduce morbidity and mortality in children with SCD.

Sickle cell disease nephropathy: an update on risk factors and potential biomarkers in pediatric patients

One of the major chronic complications of sickle cell disease (SCD) is sickle cell nephropathy. The aim of this review is to discuss the pathophysiology, natural history, clinical manifestations, risk factors, biomarkers and therapeutic approaches for sickle cell nephropathy, focusing on studies with pediatric patients. The earliest manifestation of renal disease is an increase in the glomerular filtration rate. A finding that may also be observed in early childhood is microalbuminuria. Nephrin, KIM-1, VGFs, chemokines and renin-angiotensin system molecules have emerged as potential early markers of renal dysfunction in SCD. In regards to a therapeutic approach, renin-angiotensin system inhibitors and angiotensin receptor blockers seem to be effective for the control of albuminuria in adults with SCD, although new studies in children are needed. The precise moment to begin renoprotection in SCD patients who should be treated remains to be determined.

Rapid decline in estimated glomerular filtration rate is common in adults with sickle cell disease and associated with increased mortality

We evaluated the prevalence of rapid decline in kidney function, its potential risk factors and influence upon mortality in sickle cell disease (SCD) in a retrospective single-center study. Rapid decline of kidney function was defined as estimated glomerular filtration rate (eGFR) loss of >3·0 ml/min/1·73 m² per year. A multivariable logistic regression model for rapid eGFR decline was constructed after evaluating individual covariates. We constructed multivariate Cox-regression models for rapid eGFR decline and mortality. Among 331 SCD patients (median age 29 years [interquartile range, IQR: 20, 41]; 187 [56·5%] female) followed for median 4·01 years (IQR: 1·66, 7·19), rapid eGFR decline was noted in 103 (31·1%). History of stroke (odds ratio [OR]: 2·91, 95% confidence interval [CI]: 1·25-6·77) and use of angiotensin converting enzyme inhibitors/angiotensin receptor blockers (OR: 3·17, 95% CI: 1·28-7·84) were associated with rapid eGFR decline. The rate of eGFR change over time was associated with mortality (hazard ratio [HR]: 0·99, 95% CI: 0·984-0·995, P = 0·0002). In Cox-regression, rapid eGFR decline associated with mortality (HR: 2·07, 95% CI: 1·039-4·138, P = 0·04) adjusting for age, sex and history of stroke. Rapid eGFR decline is common in SCD and associated with increased mortality. Long-term studies are needed to determine whether attenuating loss of kidney function may decrease mortality in SCD.