Early markers of renal dysfunction in patients with sickle cell/beta-thalassemia

Proteomic analyses of urinary exosomes identify novel potential biomarkers for early diagnosis of sickle cell nephropathy, a sex-based study

Sickle cell nephropathy (SCN) is a leading cause of morbidity and mortality in sickle cell disease (SCD). Early intervention is crucial for mitigating its effects. However, current diagnostic methods rely on generic tests and may not detect SCN until irreversible renal damage occurs. Therefore, specific biomarkers for early diagnosis of SCN are needed. Urinary exosomes, membrane-bound vesicles secreted by renal podocytes and epithelial cells, contain both common and cell type-specific membrane and cytosolic proteins, reflecting the physiologic and pathophysiologic states of the kidney. Using proteomics, we analyzed the proteomes of urinary exosomes from humanized SCD mice at 2 months (without albuminuria) and 4 months (with albuminuria) of age. Excretion of 164 proteins were significantly increased and 176 proteins was significantly decreased in the exosomes when mice developed albuminuria. Based on the relevance to SCD, chronic kidney disease and Western blot confirmation in mice, we analyzed protein abundance of heparanase, cathepsin C, α2-macroglobulin and sarcoplasmic endoplasmic Ca2+ ATPase-3 (SERCA3) in the urinary exosomes and urine of 18 SCD subjects without albuminuria and 12 subjects with albuminuria using Western blot analyses. Both male and female subjects increased or tended to increase the excretion of these proteins in their urinary exosomes upon developing albuminuria, but female subjects demonstrated stronger correlations between the excretion of these proteins and urine albumin creatinine ratio (UACR) compared to male subjects. In contrast, exosomal excretion of Tamm-Horsfall protein, β-actin and SHP-1 was independent of albuminuria. These findings provide a foundation for a time-course study to determine whether increases in the levels of these proteins precede the onset of albuminuria in patients, which will help determine the potential of these proteins as biomarkers for early detection of SCN.

Clinicopathologic Study of Sickle Cell-associated Kidney Disease: A Nigerian Experience

BACKGROUND

Improvements in sickle cell disease (SCD) care have resulted in the survival of many patients into adulthood, although this is accompanied by the increased incidence of end-organ damage, including chronic kidney disease (CKD).

OBJECTIVES

This study assessed the prevalence, pattern and predictors of renal dysfunction in SCD patients and investigated the associated renal histopathologic changes.

METHODS

We evaluated 105 patients with SCD, for proteinuria, estimated glomerular filtration rate (eGFR), and tubular dysfunction. Renal biopsy was conducted on 22 patients who qualified. Data were analysed using SPSS package version 23.

RESULTS

Thirty-seven (35.2%) of the 105 patients had CKD, as defined by an eGFR of 60 ml/min/1.73 m2 and/or proteinuria. The fractional excretion of potassium (FEK) was elevated in all patients, whereas the fractional excretion of sodium (FENa) was elevated in 98.1%. Glomerular filtration rate was negatively correlated with irreversible percentage sickle cell count (r = -0.616, P = 0.0001), FEK (r = -0.448, P = 0.0001) and FENa (r = -0.336, P = 0.004). Age, irreversible percentage sickle cell count, haemoglobin levels and FENa were the major predictors of CKD. The histological pattern in the 22 patients who had biopsies was consistent with mesangioproliferative glomerulonephritis 11 (50%), minimal change disease 6 (27.3%), focal segmental glomerulosclerosis 3 (13.6%) and interstitial nephritis 2 (9.1%).

CONCLUSIONS

CKD was prevalent in SCD patients, and it was characterised by tubular dysfunction and mesangioproliferative glomerulonephritis. The main predictors of CKD were increased age, severity of vaso-occlusive crisis, worsening anaemia and tubular dysfunction.

Frequency, pattern, and associations of renal iron accumulation in sickle/β-thalassemia patients

We evaluated frequency, pattern, and associations of renal iron accumulation in sickle/β-thalassemia. Thirty-three sickle/β-thalassemia patients (36.5 ± 14.7 years; 13 females), 14 homozygous sickle cell disease (SCD) patients, and 71 thalassemia major (TM) patients, enrolled in the E-MIOT Network, underwent magnetic resonance imaging. Iron overload (IO) was quantified by the T2* technique. Sickle/β-thalassemia patients had a significantly lower frequency of renal IO (T2* < 31 ms) than homozygous SCD patients (9.1% vs. 57.1%; P = 0.001), besides having similar hepatic, cardiac and pancreatic IO. Kidney T2* values were comparable between regularly transfused sickle/β-thalassemia and TM patients but were significantly lower in regularly transfused homozygous SCD patients than in the other two groups. In sickle/β-thalassemia patients, global renal T2* values were not associated with age, gender, splenectomy, and presence of regular transfusions or chelation. No correlation was detected between renal T2* values and serum ferritin levels or iron load in the other organs. Global renal T2* values were not associated with serum creatinine levels but showed a significant inverse correlation with serum lactate dehydrogenase (R =  - 0.709; P < 0.0001) and indirect bilirubin (R =  - 0.462; P = 0.012). Renal IO is not common in sickle/β-thalassemia patients, with a prevalence significantly lower compared to that of homozygous SCD patients, but with a similar underlying mechanism due to the chronic hemolysis.

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.

Proteomic discovery in sickle cell disease: Elevated neurogranin levels in children with sickle cell disease

PURPOSE

Sickle cell disease (SCD) is an inherited hemoglobinopathy that causes stroke and silent cerebral infarct (SCI). Our aim was to identify markers of brain injury in SCD.

EXPERIMENTAL DESIGN

Plasma proteomes were analyzed using a sequential separation approach of hemoglobin (Hb) and top abundant plasma protein depletion, followed by reverse phase separation of intact proteins, trypsin digestion, and tandem mass spectrometry. We compared plasma proteomes of children with SCD with and without SCI in the Silent Cerebral Infarct Multi-Center Clinical Trial (SIT Trial) to age-matched, healthy non-SCD controls.

RESULTS

From the SCD group, 1172 proteins were identified. Twenty-five percent (289/1172) were solely in the SCI group. Twenty-five proteins with enriched expression in the human brain were identified in the SCD group. Neurogranin (NRGN) was the most abundant brain-enriched protein in plasma of children with SCD. Using a NRGN sandwich immunoassay and SIT Trial samples, median NRGN levels were higher at study entry in children with SCD (0.28 ng/mL, N = 100) compared to control participants (0.12 ng/mL, N = 25, p < 0.0004).

CONCLUSIONS AND CLINICAL RELEVANCE

NRGN levels are elevated in children with SCD. NRGN and other brain-enriched plasma proteins identified in plasma of children with SCD may provide biochemical evidence of neurological injury.

Predictors associated with sickle cell nephropathy: a systematic review

INTRODUCTION

Sickle cell anemia affects more than 30 million people worldwide. Chronic kidney disease develops in 40% of individuals. The death rate of patients with sickle nephropathy is still high, with little known predictors related to its development. To answer the question "What predictors are associated with the onset of chronic kidney disease in patients with sickle cell anemia?", this article seeks to contribute to a better understanding of sickle nephropathy, making possible a new look at the sickle cell anemia and its kidney complications.

METHODS

A systematic review was developed, using the PRISMA recommendation, for cohort studies on predictors related to the outcome of sickle nephropathy in patients with sickle cell anemia.

RESULTS

Initially 321 studies were identified in Pubmed, of which six were selected to compose this systematic review. Lower hemoglobin levels, increased ages and albuminuria were the most pointed predictors associated with chronic kidney disease.

CONCLUSION

The main predictors associated with the development of chronic kidney disease in individuals with sickle cell anemia were lower hemoglobin levels, increased ages, and albuminuria. New studies evaluating predictors for the development of chronic kidney disease in sickle cell anemia are needed to better understand its installation and prevent its progression.

Do We Store Packed Red Blood Cells under "Quasi-Diabetic" Conditions?

Red blood cell (RBC) transfusion is one of the most common therapeutic procedures in modern medicine. Although frequently lifesaving, it often has deleterious side effects. RBC quality is one of the critical factors for transfusion efficacy and safety. The role of various factors in the cells’ ability to maintain their functionality during storage is widely discussed in professional literature. Thus, the extra- and intracellular factors inducing an accelerated RBC aging need to be identified and therapeutically modified. Despite the extensively studied in vivo effect of chronic hyperglycemia on RBC hemodynamic and metabolic properties, as well as on their lifespan, only limited attention has been directed at the high sugar concentration in RBCs storage media, a possible cause of damage to red blood cells. This mini-review aims to compare the biophysical and biochemical changes observed in the red blood cells during cold storage and in patients with non-insulin-dependent diabetes mellitus (NIDDM). Given the well-described corresponding RBC alterations in NIDDM and during cold storage, we may regard the stored (especially long-stored) RBCs as “quasi-diabetic”. Keeping in mind that these RBC modifications may be crucial for the initial steps of microvascular pathogenesis, suitable preventive care for the transfused patients should be considered. We hope that our hypothesis will stimulate targeted experimental research to establish a relationship between a high sugar concentration in a storage medium and a deterioration in cells’ functional properties during storage.

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.

End points for sickle cell disease clinical trials: renal and cardiopulmonary, cure, and low-resource settings

To address the global burden of sickle cell disease and the need for novel therapies, the American Society of Hematology partnered with the US Food and Drug Administration to engage the work of 7 panels of clinicians, investigators, and patients to develop consensus recommendations for clinical trial end points. The panels conducted their work through literature reviews, assessment of available evidence, and expert judgment focusing on end points related to patient-reported outcome, pain (non-patient-reported outcomes), the brain, end-organ considerations, biomarkers, measurement of cure, and low-resource settings. This article presents the findings and recommendations of the end-organ considerations, measurement of cure, and low-resource settings panels as well as relevant findings and recommendations from the biomarkers panel.

Urinary Metabolic Profile of Patients with Transfusion-Dependent β-Thalassemia Major Undergoing Deferasirox Therapy

INTRODUCTION

Renal dysfunction is a frequent complication in patients suffering from β-thalassemia major (β-TM). The aim of this study was to analyze the renal function and urine metabolomic profile of β-TM patients undergoing transfusions and deferasirox (DFX) therapy, in order to better characterize and shed light on the pathogenesis of renal disease in this setting.

METHODS AND SUBJECTS

40 patients affected by β-TM treated with DFX and 35 age- and gender-matched healthy controls were enrolled in the study. Renal function was assessed. Glomerular filtration rate (GFR) was estimated with CKD-EPI and Schwartz formula for adults and children, respectively. Renal tubular function and maximal urine concentration ability were tested. Urine specimens were analyzed by nuclear magnetic resonance spectroscopy to identify the urinary metabolite profiles.

RESULTS

The study of renal function in β-TM patients revealed normal estimated (e)GFR mean values and the albumin-to-creatinine ratio was <30 mg/g. The analysis of tubular function showed normal basal plasma electrolyte levels; 60% of patients presented hypercalciuria and many subjects showed defective urine concentration. Several amino acids, N-methyl compounds, and organic acids were overexcreted in the urine of thalassemic patients compared with controls.

DISCUSSION

The major finding of this work is that β-TM patients and controls exhibit different concentrations of some metabolites in the urine. Early recognition of urinary abnormalities may be useful to detect and prevent kidney damage.

Early Predictors of Renal Dysfunction in Pediatric Patients with Sickle Cell Disease

Sickle cell disease (SCD) is a hereditary hemoglobinopathy characterized by abnormal hemoglobin production which leads to hemolytic anemia and intermittent occlusion of small blood vessels, which further leads to tissue ischemia, chronic organ damage, and organ dysfunction including urinary system. To measure the serum levels of cystatin-C and beta 2 microglobulin in pediatric patients with SCDand to investigate their significance as early biomarkers of glomerular and/or renal tubular dysfunction. This study was conducted among 70 children with SCD and 40 age and sex-matched children as a control group. All subjects underwent a full medical history, through physical examination, laboratory investigations including blood urea, serum creatinine, serum ferritin, estimated glomerular filtration rate (eGFR) using the Schwartz formula, creatinine clearance, urinary albumin/creatinine ratio, serum cystatin-C, and β-2 microglobulin levels. Pediatric patients with SCD had significantly higher serum cystatin-C and β-2 microglobulin levels compared to controls. In addition, serum cystatin-C and β-2 microglobulin levels were positively correlated with blood urea, serum creatinine, serum ferritin, urinary albumin/creatinine ratio, duration of iron chelating agents and frequency of blood transfusion/year. Serum cystatin-C and β-2 microglobulin levels were negatively correlated with hemoglobin. Our data concluded that serum cystatin-C and β-2 microglobulin had highersensitivity and specificity (91%, 90% and 85.7%, 100%, respectively) than serum creatinine (79% and85%, respectively). Serum Cystatin-C and β-2 microglobulin are early specific and sensitive biomarkers for evaluating glomerular and tubular dysfunction in children with SCD.

Renal complications in thalassemia

Thalassemia is a disease with an extensive morbidity profile affecting almost every organ system. Renal involvement, once considered rare, is an underestimated and poorly studied complication that has been on the rise ever since medical advances granted patients longer life spans. Several studies and reports have emerged recently to shed light on the seriousness of this complication, although data is still lacking in terms of pathophysiology, diagnosis, prevention and treatment. In this review, we evaluate and compare renal involvement in the transfusion-dependent and independent variants of β-Thalassemia, highlighting the pathophysiology of kidney damage that involves iron overload, chronic anemia, and iron chelation therapy. An in-depth and focused review of the types of injuries incurred is also presented along with the diagnostic biomarkers accompanying each type of injury. Most research so far has focused on the transfusion-dependent thalassemia population being the group with most renal involvement, however recent reports have shown evidence of comparable, if not worse, involvement of the non-transfusion dependent population, sometimes leading to end-stage renal disease. As such, we try to shed light on distinct renal involvements in NTDT whenever available.

Renal iron deposition by magnetic resonance imaging in pediatric β-thalassemia major patients: Relation to renal biomarkers, total body iron and chelation therapy

BACKGROUND

The reciprocal of multiecho gradient-echo (ME-GRE) T2* magnetic resonance imaging (MRI) R2*, rises linearly with tissue iron concentration in both heart and liver. Little is known about renal iron deposition in β-thalassemia major (β-TM).

AIM

To assess renal iron overload by MRI and its relation to total body iron and renal function among 50 pediatric patients with β-TM.

METHODS

Serum ferritin, serum cystatin C, urinary albumin creatinine ratio (UACR), and urinary β2-microglobulin (β2 M) were measured with calculation of β2 M/albumin ratio. Quantification of liver, heart and kidney iron overload was done by MRI.

RESULTS

Serum cystatin C, UACR and urinary β2 microglobulin as well as urinary β2m/albumin were significantly higher in β-TM patients than the control group. No significant difference was found as regards renal R2* between Patients with mean serum ferritin above 2500 μg/L and those with lower serum cutoff. Renal R2* was higher in patients with poor compliance to chelation therapy and positively correlated to indirect bilirubin, LDH, cystatin C and LIC but inversely correlated to cardiac T2*.

CONCLUSION

kidney iron deposition impairs renal glomerular and tubular functions in pediatric patients with β-TM and is related to hemolysis, total body iron overload and poor compliance to chelation.

Role of serum cystatin-C and beta-2 microglobulin as early markers of renal dysfunction in children with beta thalassemia major

BACKGROUND

Although advancements have been made in the management of thalassemic patients, many unrecognized complications have emerged, such as renal abnormalities.

AIM

To measure serum levels of cystatin-C and β-2 microglobulin in children with beta-thalassemia major (β-TM) and investigate their significance as early markers of glomerular and tubular dysfunctions.

SUBJECTS AND METHODS

The study was performed on 70 children with (β-TM) and 20 apparently healthy children matched for age and sex as a control group. For all the enrolled children, a comprehensive medical history was obtained and complete physical examination was performed, blood urea, serum creatinine, serum ferritin, estimated glomerular filtration rate (eGFR) by Schwartz formula and creatinine clearance, albumin/creatinine ratio in urine, serum cystatin-C levels and β-2 microglobulin were measured.

RESULTS

Thalassemic children had significantly higher cystatin-C and β-2 microglobulin levels compared with control. In addition, serum cystatin-C and β-2 microglobulin were positively correlated with urea, creatinine, serum ferritin, albumin/creatinine ratio, duration of chelation therapy and frequency of blood transfusion/year and negatively correlated with creatinine clearance, hemoglobin, and eGFR. Our data demonstrated that cystatin-C and β-2 microglobulin had higher sensitivity and specificity (91.4%, 90.0%, and 85.7%, 100%, respectively) than serum creatinine and creatinine clearance (83.0%, 100% and 81.4%, 100%, respectively) for small changes in GFR.

CONCLUSION

Cystatin-C and β-2 microglobulin are specific and sensitive early biomarkers for monitoring glomerular and tubular dysfunction in children with β-TM.

Losartan for the nephropathy of sickle cell anemia: A phase-2, multicenter trial

Nephropathy is a common and progressive complication of sickle cell anemia (SCA). In SCA mice, we found that hyperangiotensinemia in the absence of hypertension underlies nephropathy, and its downregulation by losartan, an angiotensin-II-receptor-1 blocker, reduced albuminuria and progression of nephropathy. Therefore, we performed a phase-2 trial of oral losartan, given for 6 months, to explore whether it reduced albuminuria in children and adults with SCA. Participants were allocated to groups defined by class of baseline urinary albumin-to-creatinine ratio (UACR): no albuminuria (NoA), microalbuminuria (MicroA), and macroalbuminuria (MacroA). The primary endpoint was a ≥25% reduction UACR from baseline. There were 32 evaluable participants (mean age 24 years; NoA = 14, MicroA = 12, MacroA = 6). The primary endpoint was met in 83% of the MacroA group (P < 0.0001) and 58% of the MicroA group (P < 0.0001). Median fold-change in UACR was -0.74 for MacroA and -0.46 for MicroA. In MacroA and MicroA, UACR classification improved in 50% but worsened in 11%. Urine osmolality and estimated glomerular filtration rate (eGFR) did not change significantly. Losartan was discontinued in three participants [leg cramps, N = 1; decline in eGFR >25% (142➝104 mL/minute/1.73 m² ), N = 1; rise in serum creatinine >50% (0.2➝0.3 mg/dL), N = 1]. Albuminuria was associated with diastolic dysfunction and impaired functional capacity, although cardiopulmonary status was unchanged after 6 months of losartan therapy. In summary, losartan decreased urinary albumin excretion in most participants with albuminuria. Those with macroalbuminuria had the greatest benefit. This study forms the basis for a phase-3, randomized, placebo-controlled trial of losartan for the nephropathy of SCA.

Clinical Predictive Value of Cystatin C in Pediatric Sickle Cell Disease: A Marker of Disease Severity and Subclinical Cardiovascular Dysfunction

BACKGROUND

Patients with sickle cell disease (SCD) are at high risk of renal dysfunction and cardiovascular morbidity. The association between cystatin C and renal function is well known, however, cystatin C has recently emerged as a strong predictor of cardiovascular events and adverse outcomes in patients with and without kidney disease, mostly related to both inflammation and atherosclerosis.

AIM

To determine cystatin C levels in 53 children and adolescents with SCD compared to 40 age- and sex-matched healthy controls and assess its relation to markers of hemolysis, iron overload, sickle vasculopathy, and carotid intima-media thickness (CIMT).

METHODS

Patients with SCD in steady state were studied, focusing on hydroxyurea therapy, hematological profile, serum ferritin, high-sensitivity C-reactive protein (hs-CRP), urinary albumin-creatinine ratio (UACR), and serum cystatin C. Echocardiography and CIMT were assessed using high-resolution ultrasound. Heart disease was defined by systolic left ventricle dysfunction (shortening fraction <30% or ejection fraction <55%).

RESULTS

Carotid IMT was significantly higher in patients with SCD compared to controls ( P < .001). Patients with SCD having nephropathy, heart disease, or history of frequent sickling crisis (≥3 attacks/y) had significantly higher cystatin C levels than those without ( P < .05). Patients with SCD treated with hydroxyurea had lower cystatin C levels than untreated patients ( P = .039). High-sensitivity C-reactive protein, UACR, ejection fraction, and CIMT were independently related to cystatin C in multiple regression analysis. The cutoff values of cystatin C for detection of renal or cardiovascular complications were determined.

CONCLUSION

Cystatin C may be considered a biological marker for vascular dysfunction and subclinical atherosclerosis in SCD.

[Kidney and hemoglobinopathy]

Sickle-cell disease (SCD), one of the most common severe monogenic disorders into the world, is associated with an increased frequency of chronic kidney disease. SCD is caused by a point mutation in the gene encoding β globin gene which leads to the formation of hemoglobin S that polymerises after deoxygenation. HbS polymerisation is associated with erythrocyte rigidity and vaso-occlusive episodes that play a central role into SCD pathogenesis. The spectrum of renal diseases during SCD is broad and includes various renal manifestations which become more apparent with increasing age. Underlying pathophysiological processes involved in sickle cell nephropathy are multifactorial but endothelial dysfunction related to chronic hemolysis is a key factor contributing to renal involvement. Our review focuses on the pathogenesis and on the spectrum of renal manifestations occurring in SCD patients.

Changes in Urine Microalbumin-to-Creatinine Ratio in Children with Sickle Cell Disease over Time

BACKGROUND

Approximately 20% of children with sickle cell disease (SCD) have microalbuminuria (MA). Very little is known about the progression of MA in children and young adults with SCD.

METHODS

In this study, we analyzed 5-year EMR data of 373 children [with ≥2 microalbumin-to-creatinine (MA/Cr) ratio measurements] followed at the Medical University of South Carolina to determine the rate, direction, magnitude, and predictors of MA/Cr change over time.

RESULTS

Age range was 1-22 years; mean 10.2 ± 5.2 years, 49.5% were males. Median follow-up duration was 3.12 ± 1.16 years. At baseline, 328 children had normal (<20 mg/L) MA level. Forty-five (12.1%) of children had MA (≥20 mg/L), of which 91% were ≥8 years and 21 (47%) continued to have MA at the end of the study period. On the other hand, during the study period, 24 new patients developed MA and 24 normalized their MA to levels <20 mg/L. In multivariate logistic regression model, age and bilirubin levels were predictive of MA/Cr increase in patients who received at least one blood transfusion during the study period. Baseline MA level was not predictive of the change in MA/Cr.

CONCLUSION

In children and young adults, microalbuminuria is considered a marker of early renal injury. Over time, MA/Cr levels may increase or decrease. Further studies are needed to confirm our findings, assess the reliability of MA as marker of long-term renal injury, and identify high risk patients with SCD likely to have worsening of MA over time.

Endothelial nitric oxide synthase gene intron 4 VNTR polymorphism in sickle cell disease: relation to vasculopathy and disease severity

BACKGROUND

Impaired NO bioavailability represents the central feature of endothelial dysfunction, and is a common denominator in the pathogenesis of vasculopathy in sickle cell disease (SCD). Evidence indicates the contribution of 4a allele of endothelial NO synthase (eNOS) gene to cardiac and renal diseases. We studied the 27-base pair tandem repeat polymorphism in intron 4 of eNOS gene in 51 patients with SCD compared with 55 healthy controls and evaluated its role in disease severity and hemolysis-associated complications.

PROCEDURE

Transfusion history, vaso-occlusive crisis, thrombotic events, urinary albumin excretion, and echocardiography were assessed. Analysis of eNOS intron 4 gene polymorphism was performed by polymerase chain reaction.

RESULTS

The distribution of eNOS alleles and genotypes was similar between patients with SCD and controls. Compared with bb genotype, the frequency of eNOS4a allele (aa and ab genotypes) was significantly higher in patients with elevated tricuspid regurgitant velocity (TRV) (P = 0.009), nephropathy (P = 0.006), or history of cerebral stroke (P = 0.029). Logistic regression analysis revealed that eNOS4a allele was an independent risk factor for elevated TRV (P < 0.001). Patients with SCD and eNOS4a allele had higher lactate dehydrogenase, serum ferritin, D-Dimer, and von Willebrand factor antigen (P < 0.05).

CONCLUSIONS

We suggest that eNOS intron 4 gene polymorphism is related to endothelial dysfunction and vasculopathy in SCD and could provide utility for prediction of increased susceptibility to vascular complications.

Albuminuria correlates with hemolysis and NAG and KIM-1 in patients with sickle cell anemia

BACKGROUND

Although hyperfiltration and albuminuria are common pathological conditions, kidney injury (KI) biomarkers have been seldom studied in individuals with sickle cell anemia (SCA).

METHODS

We undertook a cross-sectional assessment of urine KI biomarkers in children and adults with SCA with and without albuminuria and a normal estimated glomerular filtration rate (eGFR). Albumin, KI molecule 1 (KIM-1), N-acetyl-ß-D-glucosaminidase (NAG), endothelin-1 and transforming growth factor-β1 (TGF-β1) were measured. Assays were normalized by urine creatinine. Urine intracellular hemosiderin and serum lactate dehydrogenase (LDH) were assessed as markers of hemolysis. Albuminuria was associated to the biomarkers by Pearson and Spearman correlation coefficients. Differences between the albuminuria (yes, no) groups were assessed by the t test.

RESULTS

Nineteen patients with albuminuria (mean urine albumin/creatinine 527.14 ± 1070 mg/g, range 38.3--190 mg/g) and 19 patients without albuminuria (mean urine albumin/creatinine 15.93 ± 5.17 mg/g, range 7.9-28.4 mg/g) were studied. The age range for the whole group was 11-48 years, and 47 % were males. Patients with albuminuria were older, had lower hematocrit, were more likely to test positive for urine hemosiderin and had a higher KIM-1 (P = 0.0035) and NAG/ creatinine ratios (P = 0.0062). Urine hemosiderin strongly correlated to a higher LDH level (P < 0.001).

CONCLUSIONS

Despite a normal or increased eGFR, KI biomarkers were detected in the urine of individuals with SCA. NAG, KIM-1 and urine hemosiderin correlated with the presence of albuminuria.

Early Predictors of Renal Dysfunction in Egyptian Patients with β-Thalassemia Major and Intermedia

Background

Better survival of thalassemia patients allowed previously unrecognized renal complications to emerge.

Objectives

Assess prevalence and early predictors of renal dysfunction in young β-thalassemia major (β-TM) and intermedia (β-TI) patients.

Subjects

66 β-TM (group I), 26 β-TI (group II) Egyptian patients and 40 healthy controls.

Methods

Clinical assessment and laboratory data including kidney and liver function tests, such as serum ferritin, serum bicarbonate, plasma osmolality and urinary total proteins, microalbuminuria (MAU), N-acetyl-β-D-glucosaminidase (NAG), retinol binding protein (RBP), α-1 microglobulin, bicarbonate, osmolality, creatinine clearance (CrCl), % fractional excretion of bicarbonate (% FE-HCO3).

Results

The prevalent renal abnormality was proteinuria (71%), followed by increased urinary level of RBP (69.4%), NAG (58.1%), α-1 microglobulin (54.8%) and microalbuminuria (29%) and also decreased urinary osmolality (58.1%). CrCl was a better assessment of renal function and significantly lowered in thalassemia patients. Tubular dysfunctions were more significant in splenectomized β-TM patients who showed more elevation of NAG and α-1 microglobulin and lower urinary osmolality. NAG, RBP and α-1 microglobulin were negatively correlated with CrCl and positively correlated with serum ferritin and urinary total protein. Z-score analysis for identifying patients with renal dysfunction proved superiority of urine total protein and RBP. Comparative statistics of different frequencies revealed significant difference between the urinary total protein and both MAU and % FE-HCO3.

Conclusion

Asymptomatic renal dysfunctions are prevalent in young β-TM and β-TI patients that necessitate regular screening. Urinary total protein and RBP may be cost-effective for early detection.

How I treat renal complications in sickle cell disease

Renal disease is one of the most frequent and severe complications experienced by patients with sickle cell disease; its prevalence is likely to increase as the patient population ages. We recommend regular monitoring for early signs of renal involvement and a low threshold for the use of hydroxyurea as preventative measures for end-stage renal disease. Once renal complications are detected, a careful assessment of the patient is required to rule out other causes of renal disease. Proteinuria and hypertension should be managed aggressively and the patient referred to a specialist nephrology center when progressive decline in renal function is noted. For the few patients who develop advanced chronic kidney disease, timely planning for dialysis and transplantation can significantly improve outcome, and we recommend an exchange blood transfusion policy for all patients on the transplant waiting list and for those with a functioning graft. Alongside the invasive treatment regimes, it is important to remember that renal failure in conjunction with sickle cell disease does carry a significant burden of morbidity and that focusing on symptom control has to be central to good patient care.

Renal function in transfusion-dependent pediatric beta-thalassemia major patients

PURPOSE

In this study, the relationship between glomerular and tubular function and creatinine, glomerular filtration rate (GFR) and urine NAG in thalassemia major patients aged 7-16 years was investigated.

DESIGN AND SETTING

This is a case-control study comprising 280 individuals [144 (51·4%), males; 136 (48·6%), females].

MATERIALS AND METHODS

Patients were divided in groups of 14 individuals and age groups of 7-16 years. Sodium excretion fraction, fraction excretion of potassium, calcium-to-creatinine and uric acid-to-creatinine ratios, and duration of specific blood transfusion were determined in all age groups receiving deferoxamine.

RESULTS

GFR decreased with increasing age, but the correlation was not statistically significant. There was no significant correlation between the ferritin levels and the GFR changes. The mean value of NAG activity between thalassemic patients and controls has no significant difference. The difference in mean age of the groups with high NAG activity and normal NAG activity was statistically significant. Thirty-seven patients (52·1%) in the group with normal NAG activity, and 45 patients (6·25%) in the group with NAG activity above normal were observed with uricosuric effects with no significant difference. Four patients (6·9%) in the group with normal NAG activity and six patients (7·3%) in the group with NAG activity above normal were shown to have hematuria with no significant difference. The results show that the increase in serum ferritin is significantly correlated with the increase in NAG activity (P<0·001, r = 0·2). Of patients with normal NAG activity 1 (1·7%) and with NAG activity higher than normal, 13 (15·9%) cases experienced hypercalciuria that significant difference was existing. The data also indicated that the NAG changes do not correlate with GFR changes.

CONCLUSION

The results showed that kidney dysfunction in thalassemia increases with increasing age, duration, and levels of blood transfusion and hypercalciuria. It is therefore recommended that the presence of severe renal dysfunction in thalassemic patients should be investigated using sensitive and specific tests, mainly NAG, to prevent progress towards the complications.

Renal tubular dysfunction in sickle cell disease

BACKGROUND/AIMS

Kidney abnormalities are one of the main chronic complications of sickle cell disease (SCD). The aim of this study is to investigate the occurrence of renal tubular abnormalities among patients with SCD.

METHODS

This is a prospective study with 26 SCD adult patients in Brazil. Urinary acidification and concentration tests were performed using calcium chloride (CaCl2), after a 12h period of water and food deprivation. Fractional excretion of sodium (FENa), transtubular potassium gradient (TTKG) and solute free water reabsorption (TcH2O) were calculated. The SCD group was compared to a group of 15 healthy volunteers (control group).

RESULTS

Patient`s average age and gender were similar to controls. Urinary acidification deficit was found in 10 SCD patients (38.4%), who presented urinary pH >5.3 after CaCl2 test. Urinary osmolality was significantly lower in SCD patients (355 ± 60 vs. 818 ± 202 mOsm/kg, p=0.0001, after 12h period water deprivation). Urinary concentration deficit was found in all SCD patients (100%). FENa was higher among SCD patients (0.75 ± 0.3 vs. 0.55 ± 0.2%, p=0.02). The TTKG was higher in SCD patients (5.5 ± 2.5 vs. 3.0 ± 1.5, p=0.001), and TcH2O was lower (0.22 ± 0.3 vs. 1.1 ± 0.3L/day, p=0.0001).

CONCLUSIONS

SCD is associated with important kidney dysfunction. The main abnormalities found were urinary concentrating and incomplete distal acidification defect. There was also an increase in the potassium transport and decrease in water reabsorption, evidencing the occurrence of distal tubular dysfunction. .

[Spectrum of renal manifestations in sickle cell disease]

Sickle cell disease (SCD), the most common hemoglobinopathy, is an increasing cause of chronic kidney disease. In the last decade, we have witnessed a better understanding in the characterization of clinical manifestations and pathogenesis of sickle cell nephropathy. The spectrum of renal diseases during SCD includes various renal manifestations such as impairment of urinary concentrating ability, defect in urine acidification, renal papillary necrosis and proteinuria related to glomerular injury leading to progressive end-stage renal disease. Endothelial dysfunction related to chronic hemolysis and the relative renal hypoxia caused by vaso-occlusive sickle red blood cells are probably two key factors for SCN development. Optimal therapeutic management (including the use of blockers of the renin-angiotensin system) of patients with proteinuria remains to be determined. Renal replacement therapy with dialysis is required in SCD patients with end-stage renal disease but these patients should probably undergo kidney transplantation that requires careful management.

Morbidities and mortality in transfusion-dependent Beta-thalassemia patients (single-center experience)

BACKGROUND

The improvement of quality and duration of life of transfusion-dependent B thalassemia patients over the last years discloses several complications due to the underling disorder, iron overload and the treatment with iron chelators. Our Aim was to assess the morbidity patterns and mortality rate of transfusion-dependent thalassemia patients, and compare the outcomes in relation to age of onset, type, duration, and compliance to iron chelation therapy and frequency of blood transfusion.

PROCEDURE

This retrospective study included 447 transfusion-dependent β-thalassemia patients who attended the Thalassemia Center, Ain Shams University Children's Hospital over the last 10 years in the period between January 2000 and January 2010. Data were collected from the patients or their caregivers, as well as by reviewing follow up sheets for examinations and investigations done to detect morbidities as well as iron chelation therapies given. Determination of mortality rate and the causes of death were also done.

RESULTS

Results revealed that the most common morbidities were endocrinologic (44.7%) followed by cardiovascular (41.3%) and hepatic (40.5%), then renal (4%). The different iron chelation therapy groups showed a comparable prevalence of different morbidities. The mortality rate was 1.5% and infection was the most common cause of death. The 5, 10, 20 years' survival rate among the studied patients was 80%, 50%, 20%, respectively.

CONCLUSION

In the past 10 years, the survival and morbidity rates in our center have markedly improved as a result of regular blood transfusion, new iron chelators, and better compliance of the patients.

Sickle cell nephropathy: challenging the conventional wisdom

This review explores the current model of sickle cell nephropathy and the limitations of the model. Renal abnormalities are common complications of sickle cell disease (SCD). Beginning in childhood, patients with SCD develop a urinary concentrating defect resulting in polyuria and a predisposition to nocturnal enuresis and dehydration. The current model of sickle cell nephropathy suggests that destruction of the renal medulla induces production of renal vasodilating substances that feedback to the glomerulus causing hyperfiltration. Hyperfiltration leads to glomerulosclerosis and proteinuria, with eventual reduction in kidney function. The crucial steps of vasodilating substance production and hyperfiltration in children with SCD have not been proven. Treatment of sickle cell nephropathy is aimed at the reduction of proteinuria with angiotensin converting enzyme inhibitors or angiotensin receptor blockers. Hydroxyurea and chronic transfusion therapy may also alter the progression of sickle cell nephropathy in children. Further studies are needed to identify an accurate model and effective treatments for sickle cell nephropathy.

Sickle cell nephropathy - a practical approach

Despite its apparently simple molecular aetiology, sickle cell disease (SCD) has long been known to have a remarkably variable clinical course, with complications involving many organs including the kidneys. Whilst many affected individuals show no evidence of renal involvement into late adulthood, others develop renal dysfunction in childhood or early adult life with a significant proportion eventually requiring renal replacement therapy. This review explores the pathophysiology and clinical manifestations of sickle cell nephropathy (SCN) and discusses how each complication can be investigated, monitored and managed in the outpatient setting. We summarize current knowledge of genetic modulation of sickle-related renal dysfunction. We outline the evidence for various treatment options and discuss others for which little evidence currently exists.

New insights on pathophysiology, clinical manifestations, diagnosis, and treatment of sickle cell nephropathy

Sickle cell nephropathy is one of the main chronic complications of sickle cell disease (SCD), the most common of the hematological hereditary disorders. Several studies have been performed since the first description of SCD 100 years ago to investigate the mechanisms of kidney involvement in this disease. It has been demonstrated that both glomerular and tubular compartments can be damaged as a direct consequence of SCD, including renal function loss, concentration and acidification deficits, and glomerulopathies. This article highlights the aspects of sickle cell nephropathy pathophysiology and clinical manifestations and describes the most recent advances in the diagnosis and treatment of this disorder.

Fok-I polymorphism of vitamin D receptor gene and the presence of renal dysfunction in patients with β-thalassemia major

Recent evidence supports the presence of renal dysfunction even among young patients with β-thalassemia major. However, the possible genetic contribution has never been investigated. The aim of this study was to correlate the presence of Fok-I polymorphism of the vitamin D receptor gene with abnormal levels of early markers of renal impairment in children and young adults with thalassemia. Thirty-four patients (19 male and 15 female) with β-thalassemia major on conventional treatment, with a mean decimal age of 14.62 ± 5.47 years (range: 5-22 years), were included in the study. Markers of renal function were determined in serum and in urine and patients were genotyped for Fok-I gene polymorphism. Genotype frequencies were similar to those previously reported for other populations: 47.06% of the patients were homozygous for the F allele, 41.18% were heterozygous, and 11.76% were homozygous for the f allele. A considerable number of patients demonstrated impaired renal function with increased serum cystatin C levels (29.41%), glomerular dysfunction with proteinuria (68%), as well as significant tubulopathy with hypercalciuria (73.08%), and increased levels of urinary β(2)-microglobulin (29.41%). When patients were stratified according to Fok-I polymorphism, a significantly higher prevalence of abnormally increased serum levels of cystatin C was observed in patients being homozygous for the f allele (75%) compared with those being heterozygous (Ff) or homozygous for the F allele (14.29% and 31.25%, respectively, P = .02). Further studies are needed to confirm these preliminary results and elucidate the possible mechanisms involved.

Biomarkers for early detection of sickle nephropathy

Renal complications affect nearly 30-50% of adults with sickle cell anemia (SCA), causing significant morbidity and mortality. Standard renal function tests like serum creatinine and glomerular filtration rate become abnormal in this disease only when renal damage has become extensive and largely irreversible. Moreover, not all patients develop sickle nephropathy (SN). Therefore, noninvasive biomarkers that predict early onset of SN are necessary. We performed a cross-sectional analysis for nephropathy in 116 patients with sickle cell disease, analyzing urinary kidney injury molecule-1 (KIM-1), liver-type fatty acid binding protein (L-FABP), N-acetyl-b-D-glucosaminidase (NAG), neutrophil gelatinase-associated lipocalin (NGAL) and transforming growth factor-β1 (TGF-β), together with conventional renal biomarkers (urine albumin and osmolality, and serum creatinine and cystatin C estimated GFR) during routine clinic visits when patients were at steady-state/baseline. We observed a distinct biomarker pattern: KIM-1 and NAG emerged as biomarkers with a strong association with albuminuria. Surprisingly, and in contrast to other acute/chronic renal disorders, NGAL, L-FABP, and TGF-β levels did not show any relationship with albuminuria in patients with SCA. Our study identifies potential biomarkers for SN, and suggests longitudinal validation of these biomarkers for early detection of SN, so that therapeutic interventions can be applied before renal damage becomes irreversible.

Early markers of nephrotoxicity in patients with metal-on-metal hip arthroplasty

BACKGROUND

Metal ions released from arthroplasty devices are largely cleared in urine, leading to high exposure in renal tissues. Validated early markers of renal damage are routinely used to monitor workers in heavy metal industries, and renal risk can be quantified in these industries. It is unclear if the ion levels in patients with metal-on-metal hips are sufficient to cause renal damage.

QUESTION

Does metal-on-metal (MOM) bearing use over a 10-year period lead to elevation of early renal markers compared with the levels expected in subjects with no metal exposure?

METHODS

We retrospectively reviewed 31 patients who underwent MOM hip resurfacings 10 years earlier. Whole blood specimens were collected for metal ion analysis, serum for creatinine estimation, and urine for timed metal ion output and renal markers. The renal marker levels of 30 age- and gender-matched subjects with no metal exposure and no known renal problems or diabetes mellitus were used as controls for renal markers.

RESULTS

Median serum creatinine level in the MOM group was 1.1 mg/dL (interquartile range, 1.0-1.2 mg/dL) and median creatinine clearance was 79.2 mL/min. In this cohort, the number of patients with markers of renal damage above the reference range was comparable to the controls. None of the renal markers were associated with metal levels.

CONCLUSION

The absence of elevation of renal markers in this cohort 10 years after MOM bearing implantation is reassuring. However, we believe surveillance through further longer-term, large-scale controlled trials are needed to monitor this arthroplasty-induced low-intensity (but long-term) trace element exposure to rule out potential nephrotoxicity.

Urinary transforming growth factor beta-1 as a marker of renal dysfunction in sickle cell disease

Renal dysfunction affects 5-18% of patients with sickle cell disease (SCD). To date, no studies have described urinary levels of transforming growth factor β-1 (TGF-β1), a marker of fibrosis, and neutrophil gelatinase-associated lipocalin (NGAL), a marker of acute/chronic kidney disease, as biomarkers in identifying patients at risk of developing renal disease in SCD. We hypothesized that SCD subjects will have increased urinary excretion of TGF-β1 and NGAL compared with healthy controls (CTR). We examined 51 SCD subjects: 42 HbSS, 8 HbSC, and 1 HbSD. Sixteen out of 42 patients with HbSS were on hydroxyurea (HU). Urinary excretion of TGF-β1 was 26.4 ± 1.5 pg/mgCr in SCD subjects vs 15.0 ± 2.4 pg/mgCr in CTR (p<0.00001). SCD patients with hemoglobin < 9 g/dl had higher urinary TGF-β1 than patients with milder anemia (p=0.002). Urinary TGF-β1 trended lower in HbSS patients treated with HU (23.61 ± 2.6 pg/mgCr), vs patients not on HU (27.69 ± 1.8 pg/mgCr; p=0.055). There was no correlation between urinary TGF-β1 and microalbuminuria or estimated glomerular function. There was no difference in urinary NGAL in SCD patients vs CTR. We suggest that urinary TGF-β1 may serve as a marker of early renal injury in SCD.

Prevalence and clinical correlates of microalbuminuria in children with sickle cell disease

Sickle cell disease (SCD) is associated with a large spectrum of renal abnormalities, one of which, microalbuminuria/proteinuria (MA/P), is a known predictor of end-stage renal disease. We studied 90 children with SCD (57% male; mean age 11.4 +/- 5.2 years) to determine the prevalence and examine clinical correlates of MA/P. The average of two spot urine microalbumin-to-creatinine samples obtained 6 months apart was recorded. Medical records were reviewed for demographic and biochemical data. Medication use, resting office blood pressures (BP), vaso-occlusive pain crises (VOC), and monthly transfusions were recorded. Fourteen children (15.5%) had MA/P. Hemoglobin (Hb) levels were significantly lower in the children with MA than in those without MA/P (8.8 +/- 1.1 vs. 9.8 +/- 1.4 g/dL, respectively) and were significantly correlated with MA (rho = 0.24, p = 0.03). Children with MA were more likely to have abnormal BP (p = 0.058), with 5/14 being hypertensive or pre-hypertensive. In a multivariate logistic regression model of MA, both Hb and BP classification remained in the final model. MA is a simple screening biomarker of early kidney injury in children with SCD. Larger studies to evaluate predictive factors of MA and the relationship to BP are needed.

Renal functions in pediatric patients with beta-thalassemia major: relation to chelation therapy: original prospective study

BACKGROUND

In beta-thalassemia, profound anemia and severe hemosiderosis cause functional and physiological abnormalities in various organ systems. In recent years, there have been few published studies mainly in adult demonstrating renal involvement in beta-thalassemia. This prospective study was aimed to investigate renal involvement in pediatric patients with transfusion dependent beta-thalassemia major (TD-betaTM), using both conventional and early markers of glomerular and tubular dysfunctions, and to correlate findings to oxidative stress and iron chelation therapy.

METHODS

Sixty-nine TD-betaTM patients (aged 1-16 years) and 15 healthy controls (aged 3-14 years) were enrolled in this study. Based on receiving chelation therapy (deferoxamine, DFO), patients were divided into two groups: group [I] with chelation (n=34) and group [II] without chelation (n=35). Levels of creatinine (Cr), calcium (Ca), inorganic phosphorus (PO4), uric acid (UA) and albumin were measured by spectrophotometer. Serum (S) levels of cystatin-C (SCysC) and total antioxidant capacity (STAC) and urinary (U) levels of beta2-microglobulin (Ubeta2MG) were measured by immunosorbent assay (ELISA). Urinary N-acetyl-beta-D-glucosaminidase (UNAG) activity and malondialdehyde (UMDA) were measured by chemical methods. Estimated glomerular filtration rate (eGFR) was determined from serum creatinine.

RESULTS

In patient with and without chelation, glomerular [elevated SCysC, SCr, Ualbumin/Cr and diminished eGFR]; and tubular dysfunctions [elevated SUA, SPO4, UNAG/Cr, Ubeta2MG/Cr] and oxidative stress marker disturbances [diminished STAC and elevated UMDA/Cr] were reported than controls. In patients with chelation, SCysC was significantly higher while, STAC was significantly lower than those without chelation. In all patients, SCysC showed significant positive correlation with SCr and negative correlation with eGFR; STAC showed significant positive correlation with eGFR and negative correlation with SCysC, SCr, UNAG/Cr; UMDA/Cr showed significant positive correlation with Ualbumin/Cr, Ubeta2MG/Cr, UNAG/Cr.

CONCLUSIONS

Our data confirm high frequency of glomerular and tubular dysfunctions in TD-betaTM pediatric patients which could be attributed to oxidative stress and DFO therapy.

Renal function in infants with sickle cell anemia: baseline data from the BABY HUG trial

OBJECTIVES

To examine the feasibility and accuracy of glomerular filtration rate (GFR) measurements in infants with sickle cell anemia (SCA).

STUDY DESIGN

The NHLBI/NICHD-sponsored Phase III randomized double-blinded placebo-controlled trial (BABY HUG) tests the hypothesis that hydroxyurea can prevent chronic organ damage in SCA. GFR elevation is a coprimary endpoint, measured quantitatively by technetium 99m-labeled diethylenetriaminepentaacetic acid (DTPA) plasma clearance and estimated by the Schwartz equation with height and creatinine.

RESULTS

Baseline DTPA GFR measurement was attempted in 191 infants; 176 of 184 completed studies (96%) were interpretable. Average age (mean +/- 1SD) was 13.7 +/- 2.6 months. Average DTPA GFR was 125.2 +/- 34.4 (range 40.2-300.9, normal 91.5 +/- 17.8 mL/min/1.73m(2)), while Schwartz estimates were higher at 184.4 +/- 55.5 mL/min/1.73m(2). DTPA GFR was correlated with Schwartz GFR (r(2) = 0.0658, P = .0012); also with age, weight, height, and kidney volume (all P < .002); but not with hemoglobin, HbF, white blood cell count, reticulocytes, medical events, or splenic function.

CONCLUSIONS

Quantitative GFR measurement is feasible but variable among infants with SCA. Schwartz GFR estimates are not highly correlated with quantitative DTPA GFR values. Baseline GFR measurements suggest that renal dysfunction in SCA, evidenced by glomerular hyperfiltration, begins during infancy.

Magnetic resonance detection of kidney iron deposition in sickle cell disease: a marker of chronic hemolysis

PURPOSE

To study the pattern, etiology, and significance of renal iron accumulation in chronically transfused sickle cell disease (SCD) and thalassemia major (TM) patients using magnetic resonance imaging (MRI).

MATERIALS AND METHODS

Magnetic resonance imaging (MRI) was performed in 75 SCD patients, 73 TM patients, and 16 healthy controls. Multiecho gradient echo protocols were used to measure T2* reciprocals (R2*) in the kidney, liver, and heart. Kidney R2* was compared to tissue iron estimates, serum iron markers, and surrogates of intravascular hemolysis by univariate regression.

RESULTS

Mean R2* in SCD patients was 55.3+/-45.3 Hz, compared with 22.1+/-11 Hz in TM patients and 21.3+/-5.8 Hz in control subjects (P<0.001). Kidney R2* decreased with advancing age (R2=0.09, P<0.02). Kidney R2* correlated strongly with increased serum lactate dehydrogenase levels found in SCD (R2=0.55, P<0.001), but was independent of hepatic iron concentration and cardiac R2*. Kidney R2* did not correlate with blood pressure, creatinine, cardiac index, or right and left ejection fraction.

CONCLUSION

Intravascular hemolysis, not chronic transfusion, causes renal hemosiderosis in SCD. Prospective trials are necessary to determine whether kidney R2* is a biomarker for hemolysis-mediated vascular complications in SCD.

Rust urine after intense hand drumming is caused by extracorpuscular hemolysis

BACKGROUND AND OBJECTIVES

During Carnival, groups of > or =60 drummers go drumming with their hands and marching for periods of 2 to 4 h. The objective of this study was to determine the frequency and type of urinary abnormalities after candombe drumming and to evaluate possible pathogenic mechanisms.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

For analysis of pathogenic mechanisms, a group of individuals were prospectively evaluated before and after candombe drumming.

METHODS

Candombe drummers were recruited in January 2006, 1 wk before prolonged drumming. After clinical evaluation, urine and blood samples were obtained before and immediately after drumming.

RESULTS

Forty-five healthy individuals (four women and 41 men), median age 31 yr (14 to 56), were evaluated. Predrumming urine and plasma samples were obtained for 30 individuals. Nineteen (42%) of 45 had a previous history of rust urine emission temporally related with candombe drumming. After drumming, 18 of 26 showed urine abnormalities; six of 26 showed rust urine, eight of 26 had microhematuria, and seven of 26 had proteinuria >1 g/L. The candombe drummers who showed rust urine after heavy drumming presented significantly higher levels of lactate dehydrogenase and total bilirubin when compared with those without urine abnormalities. Haptoglobin was significantly lower in the rust urine group. Fragmented red cells were observed in the blood smear of individuals with rust urine. Rust urine after drumming was associated with previous episodes of rust urine and glucosuria.

CONCLUSIONS

Taken together, these data confirm that rust urine is caused by extracorpuscular hemolysis.

Short-term follow-up of patients with sickle cell disease and albuminuria

BACKGROUND

Albuminuria with normal serum creatinine occurs frequently in patients with sickle cell disease (SCD), but the rate of progression to more advanced chronic renal disease is unknown. The purpose of this study was to investigate the rate of progression of children and young adults with SCD and albuminuria over time.

PROCEDURE

Urine albumin/creatinine (A/C) ratios and serum creatinine were obtained serially. Serum cystatin C levels were determined in a subgroup of 20 patients.

RESULTS

Of 38 patients with SCD who had albuminuria (30 with microalbuminuria and 8 with proteinuria), 10.5% had progressive disease during follow-up of 20 +/- 12 months. Progressive disease was observed in 2 of 30 patients with MA because MA worsened to either intermittent proteinuria (1 patient), or persistent proteinuria after 7 months follow-up (1 patient). Two of eight patients with proteinuria worsened to nephrotic-range after 8 and 17 months with elevations of serum creatinine. All eight patients with proteinuria were treated with angiotensin blockade and/or hydroxyurea. Of those, six patients responded to treatment with decreased albuminuria and no changes in serum creatinine. Serum cystatin C level trended to increase before serum creatinine in patients with proteinuria.

CONCLUSIONS

Patients with rapid progression to nephrotic-range proteinuria showed decreased kidney function. Therefore, patients with albuminuria should be monitored closely for progression, and therapy with hydroxyurea and/or angiotensin blockade should be considered for patients who develop proteinuria. Serum cystatin C appears more sensitive than serum creatinine to detect early decrease in kidney function.

Early markers of renal dysfunction in patients with beta-thalassemia major

Studies of renal involvement in thalassemia syndromes have been varied and few. The most important cause of mortality and morbidity in these patients is organ failure due to iron deposition. We report here a cross-sectional study carried out between February 2005 and February 2006 on all beta-thalassemia major patients being treated in Mofid Children's hospital, Tehran. The aim of the study was to detect renal dysfunction in these patients. The patient cohort consisted of 103 patients with various disease severities. Fresh first morning urine samples were collected and analyzed for sodium (Na), potassium (K), calcium (Ca), creatinine (Cr), phosphate, uric acid (UA), N-acetyl beta-D-glucosaminidase (NAG) and amino acids. We also carried out a complete blood count evaluation and assayed fasting blood sugar and serum ferritin, sodium, potassium, creatinine, uric acid and amino acids in all patients. The mean age of our patient cohort was 12.5+/-5.53 years and 53.4% were female. Abnormal levels of urinary NAG were detected in 35.9% of patients (confidence interval 26-45%). Abnormal levels of fractional excretion (FE)-Na, FE-K and FE-UA and abnormal urine protein Pr/Cr and urine Ca/Cr ratios were present in 29.1, 7.8, 52.4, 0.3 and 22.3% of the patients, respectively. There was a significant relationship between urinary NAG and the age of the patient (R=0.35), duration of deferoxamine therapy (R= 0.31), duration of receiving blood transfusions (R=0.34) and level of fasting blood sugar (R=0.2). We concluded that renal disorders are not rare in patients with beta-thalassemia major and that they may increase in terms of frequency with age, increased duration of transfusion and deferoxamine usage and high levels of blood sugar.

Analysis of renal impairment in children with Wilson's disease

BACKGROUND

Since the diverse manifestations of renal impairment appear in different periods of Wilson's disease, misdiagnosis or missed diagnosis is not rare. This study was undertaken to find the clinical features of renal impairment in children with Wilson's disease or hepatolenticular degeneration (HLD).

METHODS

Eighty-five children with HLD who had been treated at our department between January 1991 and June 2006 were retrospectively studied. The clinical data of 25 patients with renal impairment were analyzed.

RESULTS

In the 85 HLD patients, 34 had renal impairment. Nine of the 34 patients with D-penicillamine treatment were excluded. In the remaining 25 patients, 7 had initiated symptoms of renal impairment, 5 of them with edema, 1 with gross hematuria, and 1 with acute hemolysis and acute renal failure. Twelve of the 25 patients had proteinuria, 14 had hematuria, and 5 had both proteinuria and hematuria. Urine glucose was positive in 4 patients, urine N-acetyl-beta-D-glucosaminidase (NAG) increased in 5, and urine beta2-microglobulin increased in 6. Urine red blood cell (RBC) phase was detected in 7 patients, including glomerular hematuria in 5 patients and non-glomerular hematuria in 2. Blood urea nitrogen and creatinine increased in 1 patient. B-ultrasound revealed bilaterally enlarged kidneys in 3 patients. Kidney biopsy showed diffuse mesangial proliferation and IgA deposit in mesangial region in 1 patient. All of the 25 patients had cornea K-F ring and the level of ceruloplasmin decreased. Six patients had a family history of HLD.

CONCLUSIONS

The manifestations of renal impairment with HLD are varied. HLD should be excluded from patients with unexplained renal impairment, while those with HLD should take examinations of the kidney to identify renal impairment. We propose that renal function and urinalysis should be checked regularly in patients receiving treatment of D-penicillamine.

Diagnostic potential for urinary proteomics

Urine represents a modified ultrafiltrate of plasma, with protein concentrations typically approximately 1000-fold lower than plasma. Urine’s low protein concentration might suggest it to be a less promising diagnostic specimen than plasma. However, urine can be obtained noninvasively and tests of many urinary proteins are well-established in clinical practice. Proteomic technologies expand opportunities to analyze urinary proteins, identifying more than 1000 proteins and peptides in urine. Urine offers a sampling of most plasma proteins, with increased proportions of low-molecular-weight protein and peptide components. Urine also offers enriched sampling of proteins released along the urinary tract. Although urine presents some challenges as a diagnostic specimen, its diverse range of potential markers offers great potential for diagnosis of both systemic and kidney diseases. Examples of clinical situations where this may be of value are for more sensitive detection of kidney transplant rejection or of renal toxicity of medications.

Tools to detect and modify sickle cell nephropathy

Placement of the development of a sickle cell nephropathy in a time/event line is helped by better measures of glomerular filtration rate, tubular dysfunction, and proteinuria. Preventing or slowing the nephropathy can improve the outcome of this complication of the devastating sickle cell disease.