Real-world data of Brazilian adults with X-linked hypophosphatemia (XLH) treated with burosumab and comparison with other worldwide cohorts

BACKGROUND

Disease-related variants in PHEX cause XLH by an increase of fibroblast growth factor 23 (FGF23) circulating levels, resulting in hypophosphatemia and 1,25(OH)2 vitamin D deficiency. XLH manifests in early life with rickets and persists in adulthood with osseous and extraosseous manifestations. Conventional therapy (oral phosphate and calcitriol) improves some symptoms, but evidence show that it is not completely effective, and it can lead to nephrocalcinosis (NC) and hyperparathyroidism (HPT). Burosumab (anti-FGF23 antibody) has shown to be effective and safety in the clinical trials.

METHODS

The current real-world collaborative study evaluated genetic, clinical and laboratory data of XLH Brazilian adult patients treated with burosumab.

RESULTS

Nineteen unrelated patients were studied. Patients reported pain, limb deformities and claudication, before burosumab initiation. 78% of them were previously treated with conventional therapy. The severity of the disease was moderate to severe (15 patients with score >5). At the baseline, 3 patients presented NC (16.7%) and 12 HPT (63%). After 16 ± 8.4 months under burosumab, we observed a significant: increase in stature (p = 0.02), in serum phosphate from 1.90 ± 0.43 to 2.67 ± 0.52 mg/dL (p = 0.02); in TmP/GFR from 1.30 ± 0.46 to 2.27 ± 0.64 mg/dL (p = 0.0001), in 1,25 (OH)2 D from 50.5 ± 23.3 to 71.1 ± 19.1 pg/mL (p = 0.03), and a decrease in iPTH from 86.8 ± 37.4 pg/mL to 66.5 ± 31.1 (p = 0.002). Nineteen variants were found (10 novel). HPT tended to develop in patients with truncated PHEX variants (p = 0.06).

CONCLUSIONS

This study confirms the efficacy and safety of burosumab on XLH adult patients observed in clinical trials. Additionally, we observed a decrease in iPTH levels in patients with moderate to severe HPT at the baseline.

A comprehensive model for assessing and classifying patients with thrombotic microangiopathy: the TMA-INSIGHT score

BACKGROUND

Thrombotic Microangiopathy (TMA) is a syndrome characterized by the presence of anemia, thrombocytopenia and organ damage and has multiple etiologies. The primary aim is to develop an algorithm to classify TMA (TMA-INSIGHT score).

METHODS

This was a single-center retrospective cohort study including hospitalized patients with TMA at a single center. We included all consecutive patients diagnosed with TMA between 2012 and 2021. TMA was defined based on the presence of anemia (hemoglobin level < 10 g/dL) and thrombocytopenia (platelet count < 150,000/µL), signs of hemolysis, and organ damage. We classified patients in eight categories: infections; Malignant Hypertension; Transplant; Malignancy; Pregnancy; Thrombotic Thrombocytopenic Purpura (TTP); Shiga toxin-mediated hemolytic uremic syndrome (STEC-SHU) and Complement Mediated TMA (aHUS). We fitted a model to classify patients using clinical characteristics, biochemical exams, and mean arterial pressure at presentation.

RESULTS

We retrospectively retrieved TMA phenotypes using automatic strategies in electronic health records in almost 10 years (n = 2407). Secondary TMA was found in 97.5% of the patients. Primary TMA was found in 2.47% of the patients (TTP and aHUS). The best model was LightGBM with accuracy of 0.979, and multiclass ROC-AUC of 0.966. The predictions had higher accuracy in most TMA classes, although the confidence was lower in aHUS and STEC-HUS cases.

CONCLUSION

Secondary conditions were the most common etiologies of TMA. We retrieved comorbidities, associated conditions, and mean arterial pressure to fit a model to predict TMA and define TMA phenotypic characteristics. This is the first multiclass model to predict TMA including primary and secondary conditions.

Bartter Syndrome-Related Variants Distribution: Brazilian Data and Its Comparison with Worldwide Cohorts

BACKGROUND

Genetic testing is recommended for accurate diagnosis of Bartter syndrome (BS) and serves as a basis for implementing specific target therapies. However, populations other than Europeans and North Americans are underrepresented in most databases and there are uncertainties in the genotype-phenotype correlation. We studied Brazilian BS patients, an admixed population with diverse ancestry.

METHODS

We evaluated the clinical and mutational profile of this cohort and performed a systematic review of BS mutations from worldwide cohorts.

RESULTS

Twenty-two patients were included; Gitelman syndrome was diagnosed in 2 siblings with antenatal BS and congenital chloride diarrhea in 1 girl. BS was confirmed in 19 patients: BS type 1 in 1 boy (antenatal BS); BS type 4a in 1 girl and BS type 4b in 1 girl, both of them with antenatal BS and neurosensorial deafness; BS type 3 (CLCNKB mutations): 16 cases. The deletion of the entire CLCNKB (1-20 del) was the most frequent variant. Patients carrying the 1-20 del presented earlier manifestations than those with other CLCNKB-mutations and the presence of homozygous 1-20 del was correlated with progressive chronic kidney disease. The prevalence of the 1-20 del in this BS Brazilian cohort was similar to that of Chinese cohorts and individuals of African and Middle Eastern descent from other cohorts.

CONCLUSION

This study expands the genetic spectrum of BS patients with different ethnics, reveals some genotype/phenotype correlations, compares the findings with other cohorts, and provides a systematic review of the literature on the distribution of BS-related variants worldwide.

Baseline characteristics and evolution of Brazilian patients with atypical hemolytic uremic syndrome: first report of The Brazilian aHUS Registry

Background

Atypical hemolytic uremic syndrome (aHUS) is an ultra-rare disease. Therefore, studies involving large samples are scarce, making registries powerful tools to evaluate cases. We present herein the first analysis of the Brazilian aHUS Registry (BRaHUS).

Methods

Analysis of clinical, laboratory, genetic and treatment data from patients inserted in the BRaHUS, from 2017 to 2020, as an initiative of the Rare Diseases Committee of the Brazilian Society of Nephrology.

Results

The cohort consisted of 75 patients (40 adults and 35 pediatric). There was a predominance of women (56%), median age at diagnosis of 20.7 years and a positive family history in 8% of cases. Renal involvement was observed in all cases and 37% had low C3 levels. In the <2 years of age group, males were predominant. Children presented lower levels of hemoglobin (P = .01) and platelets (P = .003), and higher levels of lactate dehydrogenase (LDH) (P = .004) than adults. Genetic analysis performed in 44% of patients revealed pathogenic variants in 66.6% of them, mainly in CFH and the CFHR1-3 deletion. Plasmapheresis was performed more often in adults (P = .005) and 97.3% of patients were treated with eculizumab and its earlier administration was associated with dialysis-free after 3 months (P = .08).

Conclusions

The cohort of BRaHUS was predominantly composed of female young adults, with renal involvement in all cases. Pediatric patients had lower hemoglobin and platelet levels and higher LDH levels than adults, and the most common genetic variants were identified in CFH and the CFHR1-3 deletion with no preference of age, a peculiar pattern of Brazilian patients.

Recommendations for the diagnosis and management of Fabry disease in pediatric patients: a document from the Rare Diseases Committee of the Brazilian Society of Nephrology (Comdora-SBN)

Abstract Fabry disease (FD) is a genetic disease, with X-chromosome linked inheritance, due to variants in the GLA gene that encodes the α-galactosidase A (α-GAL) enzyme. The purpose of the present study was to create a consensus aiming to standardize the recommendations regarding the renal involvement of FD with guidelines on the diagnosis, screening, and treatment of pediatric patients. This consensus is an initiative of the Rare Diseases Committee (Comdora) of the Brazilian Society of Nephrology (SBN). Randomized controlled clinical studies and studies with real-life data added to the authors' experience were considered for this review. The result of this consensus was to help manage patient and physician expectations regarding treatment outcomes. Thus, this consensus document recommends the investigation of the pediatric family members of an index case, as well as cases with suggestive clinical signs. From the diagnosis, assess all possible FD impairments and grade through scales. From an extensive review of the literature including pediatric protocols and particularly evaluating pediatric cases from general studies, it can be concluded that the benefits of early treatment are great, especially in terms of neuropathic pain and renal impairment parameters and outweigh the possible adverse effects that were mainly manifested by infusion reactions.

Brazilian consensus recommendations for the diagnosis, screening, and treatment of individuals with fabry disease: Committee for Rare Diseases - Brazilian Society of Nephrology/2021

Fabry disease (FD) is an X-linked inherited disorder caused by mutations in the GLA gene encoding enzyme alpha-galactosidase A (α-Gal A). The purpose of this study was to produce a consensus statement to standardize the recommendations concerning kidney involvement in FD and provide advice on the diagnosis, screening, and treatment of adult and pediatric patients. This consensus document was organized from an initiative led by the Committee for Rare Diseases (Comdora) of the Brazilian Society of Nephrology (SBN). The review considered randomized clinical trials, real-world data studies, and the expertise of its authors. The purpose of this consensus statement is to help manage patient and physician expectations concerning the outcomes of treatment. Our recommendations must be interpreted within the context of available evidence. The decisions pertaining to each individual case must be made with the involvement of patients and their families and take into account not only the potential cost of treatment, but also concurrent conditions and personal preferences. The Comdora intends to update these recommendations regularly so as to reflect recent literature evidence, real-world data, and appreciate the professional experience of those involved. This consensus document establishes clear criteria for the diagnosis of FD and for when to start or stop specific therapies or adjuvant measures, to thus advise the medical community and standardize clinical practice.

Cysteamine bitartrate delayed-release capsules control leukocyte cystine levels and promote statural growth and kidney health in an open-label study of treatment-naïve patients <6 years of age with nephropathic cystinosis

Nephropathic cystinosis is a rare autosomal recessive lysosomal storage disease that is characterized by accumulation of cysteine and formation of crystals within cells of different organs and tissues causing systemic manifestations in childhood that include poor linear growth, ocular involvement, hypothyroidism, and progressive kidney disease. This study was a long-term, prospective open-label evaluation of twice-daily delayed release (DR) cysteamine capsules in cystinosis patients <6 years of age who were naïve to any form of cysteamine treatment. Fifteen treatment-naïve patients <6 years old (mean age 2.2 ± 1.0 years, 53% male, 73% White) were enrolled and treated with DR-cysteamine capsules for up to 18 months. Patients had clinically meaningful decreases in WBC cysteine concentration during treatment (3.2 ± 3.0 nmol ½ cystine/mg protein at Day 1 to 0.8 ± 0.8 nmol ½ cystine/mg protein at study exit), and anthropometric data improvements were consistently observed in height, weight and body surface area. Additionally, estimated glomerular filtration rate increased from 55.93 ± 22.43 ml/min/1.73 m2 at baseline to 63.79 ± 21.44 ml/min/1.73 m2 at study exit. Pharmacokinetic/Pharmacodynamic results support the use of the same starting, escalation, and maintenance doses according to body surface for children aged <6 years that are currently recommended in adults and older children. All patients experienced ≥1 adverse event(s) with vomiting (80%) and upper respiratory tract infection (53%) most frequently reported. Based on our study, patients <6 years of age with nephropathic cystinosis without prior treatment can safely and effectively initiate treatment with DR-cysteamine, a delayed-release form of cysteamine bitartrate that can be given every 12 h.

Distal Renal Tubular Acidosis Associated with Autoimmune Diseases: Reports of 3 Cases and Review of Mechanisms

Case series

Patients: Female, 29-year-old • Female, 67-year-old • Female, 30-year-old

Final Diagnosis: Distal renal tubular acidosis (dRTA)

Symptoms: Hypokalemia • metabolic acidosis

Medication: —

Clinical Procedure: Diagnosis

Specialty: Nephrology • Rheumatology

Eculizumab interruption in atypical hemolytic uremic syndrome due to shortage: analysis of a Brazilian cohort

BACKGROUND

The risk of eculizumab therapy discontinuation in patients with atypical hemolytic uremic syndrome (aHUS) is unclear. The main objective of this study was to analyze the risk of aHUS relapse after eculizumab interruption due to drug shortage in Brazil.

METHODS

We screened all the registered dialysis centers in Brazil (n = 800), willing to participate in the aHUS Brazilian shortage cohort, through electronic mail and formal invitation by the Brazilian Society of Nephrology. We included patients with aHUS whose eculizumab therapy underwent unplanned discontinuation for at least 30 days between January 1st, 2016 and December 31st, 2019 during the maintenance phase of treatment. Relapse was defined by the development of thrombocytopenia, hemolytic anemia, acute kidney injury or thrombotic microangiopathy (TMA) in a kidney biopsy.

RESULTS

We analyzed 25 episodes of exposure to risk of relapse, from 24 patients. Median age was 33 (6-53) years, 18 (72%) were female, 9 (36%) had a functioning renal graft, 5 (20%) were undergoing dialysis. CFH variant was found in 8 (32%) episodes. There were 11 relapses. The risk of relapse was 34%, 44.5% and 58% at 114, 150 and 397 days, respectively. No baseline variable was related to relapse in Cox multivariate analysis, including CFH variant.

CONCLUSIONS

In this study, the cumulative incidence of aHUS relapse at 397 days was 58% after eculizumab interruption. The presence of complement variant does not seem to be associated with a higher relapse rate. The eculizumab interruption was deemed not safe, considering that the rate of relapse was high.

COMDORA-SBN recommendations for patients with rare kidney diseases in relation to the Covid-19 pandemic

During the Covid-19 pandemic, the issue is how to maintain adequate care for people with other diseases. In this document, the SBN Rare Diseases Committee (COMDORA) gives some guidelines on the care of patients with rare kidney diseases. These patients should follow the recommendations for the general population, bearing in mind that, as they have chronic kidney disease, they are included in the risk group for more serious outcomes if they develop Covid-19. Non-essential decision-making procedures should be postponed. In stable cases under appropriate treatment, we must choose to contact our patients remotely, using teleconsultations and home exam collections (if possible). In the presence of a symptom or sign of decompensation of the underlying disease, or infection with Sars-cov-2, advise the patient to seek medical assistance. The patient should not be waiting to get worse. Changes to the prescription should only be made on a scientific basis. Dosage suspension or change is not recommended, even in cases in which the patient needs to go to a center to receive his medication; in this case, the infusion center must follow the recommendations of the Ministry of Health. If the patient develops Covid-19 and uses any drugs, check the need for dose adjustment of the routine medications. Avoid the use of antimetabolics and anti-CD20 in patients with Covid-19, as they reduce viral clearance and predispose to bacterial infections. Contact between the patient and the medical team is essential; changes are recommended only with specialized medical guidance.

Multidisciplinary approach for patients with nephropathic cystinosis: model for care in a rare and chronic renal disease

Care for patients with chronic and rare diseases is complex, especially considering the lack of knowledge about the disease, which makes early and precise diagnosis difficult, as well as the need for specific tests, sometimes of high complexity and cost. Added to these factors are difficulties in obtaining adequate treatment when available, in raising patient and family awareness about the disease and treatment compliance. Nephropathic cystinosis is among these diseases. After more than 20 years as a care center for these patients, the authors propose a follow-up protocol, which has been used with improvement in the quality of care and consists of a multidisciplinary approach, including care provided by a physician, nurse, psychologist, nutritionist and social worker. In this paper, each field objectively exposes how to address points that involve the stages of diagnosis and its communication with the patient and their relatives or guardians, covering the particularities of the disease and the treatment, the impact on the lives of patients and families, the approach to psychological and social issues and guidelines on medications and diets. This protocol could be adapted to the follow-up of patients with other rare diseases, including those with renal involvement. This proposal is expected to reach the largest number of professionals involved in the follow-up of these patients, strengthening the bases for the creation of a national protocol, observing the particularities of each case.

Thrombotic microangiopathy caused by methionine synthase deficiency: diagnosis and treatment pitfalls

BACKGROUND

Inborn errors of cobalamin (Cbl) metabolism form a large group of rare diseases. One of these, Cbl deficiency type C (CblC), is a well-known cause of thrombotic microangiopathy (TMA), especially in infants. However, there has only been a single published case of TMA associated to Cbl deficiency type G (CblG), also known as methionine synthase deficiency (MSD).

CASE DIAGNOSIS/TREATMENT

A 21-month-old boy presented with pallor and oral ulcers during episodes of upper respiratory infection (URI). Further examination revealed signs of TMA, and the patient progressed to acute renal failure (ARF). Renal biopsy showed TMA. Evaluation for infection and autoantibodies were negative. The C3 and C4 complement fractions were normal. Analysis of the bone marrow aspirate suggested megaloblastic anemia and signs of hematopoiesis activation (secondary to peripheral hemolysis). Although the serum vitamin B12 level was normal, the patient was treated with cyanocobalamin, with no improvement. The ARF and hematologic parameters improved with conservative treatment. A severe relapse occurred during the follow-up, with normal ADAMTS13 activity. The presumed diagnosis was atypical hemolytic uremic syndrome, and the patient was started on eculizumab, but his response was poor, even when the dosage was increased. At this point it was also recognized that his developmental speech was delayed. Based on these findings, whole exome sequencing was performed, leading to the detection of two novel deleterious variants in the gene coding for methionine synthase, confirming the diagnosis of MSD. Subsequent treatment consisted of elevating the patient's serum homocysteine level and starting him on hydroxicobalamin, with normalization of all hematologic parameters although the microalbuminuria remained.

CONCLUSIONS

Methionine synthase deficiency is very rare and characterized by megaloblastic anemia and neurological symptoms. We report the second case of MSD associated to TMA previously diagnosed as aHUS in which the patient had a poor response to eculizumab.

Treatment of Bartter syndrome. Unsolved issue

OBJECTIVE

To describe the results of a long-term follow-up of Bartter syndrome patients treated with different drugs.

METHOD

Patients were diagnosed according to clinical and laboratory data. Treatment protocol was potassium supplementation, sodium, spironolactone, and non-steroidal anti-inflammatory drug. Patients who developed proteinuria were converted to angiotensin conversion enzyme inhibitor. The variables evaluated for each drug were Z-score for weight and stature, proteinuria, creatinine clearance, gastrointestinal complaints, amount of potassium supplementation, serum potassium and bicarbonate levels, and findings of upper digestive endoscopy.

RESULTS

20 patients were included. Follow-up was 10.1 ± 5.2 years. 17 patients received indomethacin for 5.9 ± 5.3 years; 19 received celecoxib, median of 35 months; and five received enalapril, median of 23 months. During indomethacin, a statistically significant increase was observed in the Z-score for stature and weight, without a change in the creatinine clearance. Seven of 17 patients had gastrointestinal symptoms, and upper digestive endoscopy evidenced gastritis in three patients and gastric ulcer in four patients. During celecoxib use, a significant increase was detected in the Z-score for stature and weight and a reduction of hyperfiltration; seven patients presented gastrointestinal symptoms, and upper digestive endoscopy evidenced mild gastritis in three. During enalapril use, no significant changes were observed in the Z-score for stature, weight and creatinine clearance. The conversion to enalapril resulted in a significant reduction in proteinuria.

CONCLUSION

The authors suggest starting the treatment with celecoxib, and replacing by ACEi if necessary, monitoring the renal function. The safety and efficacy of celecoxib need to be assessed in larger controlled studies.

[Eculizumab for the treatment of atypical hemolytic uremic syndrome: case report and revision of the literature]

SHU atypical (aHUS), that is, not associated with Escherichia coli Shiga toxinproducing, is seen in 5 to 10% of cases of Hemolytic Uremic Syndrome (HUS), and can occur at any age and may be sporadic or familial. The prognosis in these cases is reserved, with high mortality and morbidity in the acute phase of the disease, and about 50% of cases can develop chronic kidney disease. The increased knowledge of the pathogenesis of aHUS (overactivation of the alternative pathway of complement), was accompanied by the appearance of a drug, eculizumab, which acts as an inhibitor of membrane attack complex. Our goal is to report a case of infant with aHUS with excellent clinical and laboratory response with the use of eculizumab. 14 month old infant, previously healthy, male, presented anemia and thrombocytopenia at 12 months of age. He was treated with corticosteroids and forwarded to our service for high blood pressure. However, the scans showed nephrotic proteinuria with renal involvement and hypoalbuminemia with direct Coombs negative. He developed anemia, thrombocytopenia, worsening of renal function and hypertension. Renal biopsy showed thrombotic microangiopathy (TMA). On the non-hemolytic anemia, thrombocytopenia and acute renal failure with histological substrate MAT, was diagnosed of aHUS. The patient received eculizumab excellent clinical and laboratory response. This case shows the importance of early diagnosis and treatment of the aHUS. Eculizumab is effective and keeps long-term remission, avoiding invasive measures such as plasmapheresis, which resolves only part of the picture.

Hemolytic-Uremic Syndrome in childhood

There is a group of diseases that may manifest with thrombotic microangiopathy and present clinical overlap. Among these we emphasize the thrombotic thrombocytopenic purpura and Hemolytic Uremic Syndrome, and the latter can occur by the action of toxins, systemic diseases, overactivation of the alternative complement system pathway, which can occur due to changes in regulatory proteins (atypical HUS) and finally, idiopathic. You must carry out a series of tests to differentiate them. aHUS is a diagnosis of exclusion of other causes of MAT. The treatment of aHUS with plasma therapy, results in most cases with good shortterm response, especially hematological; however, it is a progressive and devastating disease and can lead to death and terminal chronic renal disease. Treatment with plasma displays great recurrence of long-term disease and renal insufficiency. Eculizumab, a monoclonal antibody anti-C5, has been associated with hematological remission, benefits on renal function and no need of plasma therapy.

N-acetyl-cysteine is associated to renal function improvement in patients with nephropathic cystinosis

BACKGROUND

Nephropathic cystinosis is an autosomal recessive systemic severe disease characterized by intralysosomal cystine storage. Cysteamine is an essential component of treatment. There is solid evidence that cystine accumulation itself is not responsible for all abnormalities in cystinosis; there is also a deficiency of glutathione in the cytosol. Patients with cystinosis can be more susceptible to oxidative stress.

CASE-DIAGNOSIS/TREATMENT

The patient cohort comprised 23 cystinosis patients (16 males) aged <18 years (mean age 8.0 ± 3.6 years) with chronic kidney disease class I-IV with good adherence to treatment, including cysteamine. Oxidative stress was evaluated based on the levels of serum thiobarbituric acid-reactive substances (TBARS), and renal function was evaluated based on serum creatinine and cystatin C levels and creatinine clearance (Schwartz formula). N-Acetylcysteine (NAC), an antioxidant drug was given to all patients for 3 months (T1) at 25 mg/kg/day divided in three doses per day. The measured values at just before the initiation of NAC treatment (T0) served as the control for each patient.

RESULTS

Median serum TBARS levels at T0 and T1 were 6.92 (range 3.3-29.0) and 1.7 (0.6-7.2)  nmol/mL, respectively (p < 0.0001). In terms of renal function at T0 and T1, serum creatinine levels (1.1 ± 0.5 vs. 0.9 ± 0.5 mg/dL, respectively; p < 0.0001), creatinine clearance (69.7 ± 32.2 vs. T1 = 78.5 ± 33.9 mL/min/1.73 m(2), respectively; p = 0.006), and cystatin c level (1.33 ± 0.53 vs. 1.15 ± 0.54 mg/l, respectively; p = 0.0057) were all significantly different at these two time points. Serum creatinine measurements at 6 (T -6) and 3 months (T -3) before NAC initiation and at 3 (T +3) and 6 months (T +6) after NAC had been withdrawn were also evaluated.

CONCLUSION

During the 3-month period that our 23 cystinosis patients were treated with NAC, oxidative stress was reduced and renal function significantly improved. No side-effects were detected. Larger and controlled studies are needed to confirm these findings.

[Practical markers of renal function in cystinosis patients]

BACKGROUND

Cystinosis is an autossomic recessive systemic disease that leads to renal insufficiency early in life unless cysteamine be started early. Unfortunately, even in this situation the patients will develop chronic renal disease with need of renal replacement therapy about second decade of life. Therefore, the renal function evaluation is essential to these patients. The aim of this study was to evaluate cystatin C, serum creatinine and creatinine clearance estimated by stature (Schwartz Formula) in cystinosis patients, with different degrees of renal function, and to correlate these parameters.

METHODS

We studied cystinosis patients, aged lower than 18 years, with different degrees of renal function, classified according to KDOQI in Chronic Kidney Disease stage 1 to 4. No patient was under renal replacement therapy. In these patients we evaluate the serum creatinine, cystatin C and creatinine clearance according to Schwartz Formula.

RESULTS

We analyzed 103 blood samples of 26 patients. We detected a significant statistical correlation between serum creatinine and cystatin C (r = 0.81, p < 0.0001), cystatin C and creatinine clearance estimated by stature (r = -0.84, p < 0.0001) and between serum creatinine and creatinine clearance estimated by stature (r = -0.97, p < 0.0001).

CONCLUSIONS

The expensive measurement of cystatin C showed no advantage in relation to serum creatinine and creatinine clearance according to Schwartz Formula in cystinosis patients to estimate the glomerular filtration rate. This is the first report checking the value of serum creatinine, creatinine clearance estimated by stature and cystatin C in cystinosis patients.

Pharmacokinetics of cyclosporin--a microemulsion in children with idiopathic nephrotic syndrome

OBJECTIVE

We present a prospective study of a microemulsion of cyclosporin to treat idiopathic nephrotic syndrome in ten children with normal renal function who presented cyclosporin trough levels between 50 and 150 ng/ml and achieved complete remission with cyclosporin. To compare the pharmacokinetic parameters of cyclosporin in idiopathic nephrotic syndrome during remission and relapse of the nephrotic state.

METHOD

The pharmacokinetic profile of cyclosporin was evaluated with the 12-hour area under the time-concentration curve (auc0-12) using seven time-point samples. This procedure was performed on each patient during remission and relapse with the same cyclosporin dose in mg/kg/day. The 12-hour area under the time-concentration curve was calculated using the trapezoidal rule. All of the pharmacokinetic parameters and the resumed 4-hour area under the time-concentration curve were correlated with the 12-hour area under the time-concentration curve. ClinicalTrials.gov: NCT01616446.

RESULTS

There were no significant differences in any parameters of the pharmacokinetic of cyclosporin during remission and relapse, even when the data were normalized by dose. The best correlation with the 12-hour area under the time-concentration curve was the 4-hour area under the time-concentration curve on remission and relapse of the disease, followed by the 2-hour level after cyclosporin (c2) dosing in both disease states.

CONCLUSIONS

These data indicate that the same parameters used for cyclosporin therapeutic monitoring estimated during the nephrotic state can also be used during remission. Larger controlled studies are needed to confirm these findings.

The long-term use of enalapril and hydrochlorothiazide in two novel mutations patients with Dent's disease type 1

Dent's disease type 1 is an X-linked tubular disease caused by mutations in the renal chloride channel CLCN-5, and it is characterized by low molecular weight proteinuria, hypercalciuria, nephrocalcinosis, and renal failure. Several cases have been described in which the only presenting symptoms were asymptomatic proteinuria, and focal segmental or global glomerulosclerosis. The renal failure in these patients may be caused by hypercalciuria and persistent proteinuria. Therefore, angiotensin converse enzyme inhibitor and thiazides could be useful. Our aim is to report the effects of these drugs in two novel mutations patients with Dent's disease type 1. In this report, no significant correlations between dosage of hydrochlorothiazide and calciuria and no significant correlations between proteinuria and dosage of enalapril were detected. This is important since these are polyuric patients and these drugs could be dangerous to their renal function.

Oxidative stress in cystinosis patients

Background/Aims

Nephropathic cystinosis (NC) is a severe systemic disease and cysteamine improves its prognosis. Lysosomal cystine accumulation is the hallmark of cystinosis and is regarded as the primary defect due to mutations in the CTNS gene. However, there is great evidence that cystine accumulation itself is not responsible for all abnormalities observed in NC. Studies have demonstrated altered ATP metabolism, increased apoptosis, and cell oxidation. An increased number of autophagosomes and autophagic vacuoles have been observed in cystinotic fibroblasts and renal epithelial cells, suggesting that altered autophagy plays a role in NC, leading to increased production of reactive oxygen species. Therefore, cystinosis patients can be more susceptible to oxidative stress (OS) and it can contribute to the progression of the renal disease. Our goal was to evaluate a marker of OS (serum TBARS) in NC children, and to compare the results with those observed in healthy controls and correlated with renal function parameters.

Methods

The study included patients aged under 18 years, with good adherence to the treatment and out of renal replacement therapy. The following parameters were evaluated: serum creatinine, BUN, creatinine clearance estimated by stature and serum TBARS levels.

Results

We selected 20 patients aged 8.0 ±3.6 years and observed serum TBARS levels of 4.03 ±1.02 nmol/ml. Serum TBARS levels in the 43 healthy controls, aged 7.4 ±1.1 years, were 1.60 ±0.04 nmol/ml. There was a significant difference between the plasma TBARS levels among the 2 groups (p < 0.0001). We detected no significant correlation between plasma TBARS levels and renal function.

Conclusion

An increased level of serum TBARS in patients with NC was observed and this abnormality was not correlated with the renal function status degree. This is the first report that shows increased oxidative stress in serum of NC patients.

Miosite e rabdomiólise na doença mão-pé-boca na infância

OBJETIVO: Relatar um caso de doença mão-pé-boca complicada por miosite, rabdomiólise e hepatite, interessante por ser a doença frequente em crianças e poder apresentar complicações graves, apesar de raras. DESCRIÇÃO DO CASO: Paciente de três anos de idade, sexo feminino, com história de febre por três dias, seguida pelo aparecimento de lesões ulceradas em mucosa oral e mialgia intensa. Após três dias, voltou a apresentar febre por mais dois dias (febre bifásica). Nesses dois dias, apresentou lesões eritematosas pelo corpo, principalmente nos pés, mãos e face, e procurou atendimento médico. Evoluiu com aumento de enzimas musculares e hepáticas (CPK com valor máximo de 345.007U/L, TGO 2041U/L, TGP 1589U/L, gama-GT 94U/L) e aumento transitório da creatinina sérica, com clearance de creatinina estimado pela estatura de 73mL/minuto/1,73m2 de superfície corporal. Houve melhora progressiva, com hidratação vigorosa e alcalinização da urina, sem necessidade de diálise. COMENTÁRIOS: Trata-se de uma criança com doença mão-pé-boca, com miosite, rabdomiólise e hepatite. São enfatizados os critérios clínicos laboratoriais para o diagnóstico e a importância da monitorização das complicações da doença

Dental abnormalities and oral health in patients with Hypophosphatemic rickets

INTRODUCTION

Hypophosphatemic rickets represents a group of heritable renal disorders of phosphate characterized by hypophosphatemia, normal or low serum 1,25 (OH)2 vitamin D and calcium levels. Hypophosphatemia is associated to interglobular dentine and an enlarged pulp chambers.

AIM

Our goal was to verify the dental abnormalities and the oral health condition in these patients.

MATERIAL AND METHODS

Prospective study of oral conditions in patients with Hypophosphatemic rickets. This report employed a simple method to be easily reproducible: oral clinical exam and radiographic evaluation.

RESULTS

Fourteen patients were studied, 5 males, median age of 11 years (4 to 26). Occlusion defects (85,7%) and enamel hypoplasia (57,1%) were significant more frequently than dental abscesses (one patient). We observed enlarged pulp chambers in 43% of the patients and hypoplasia and dentin abnormalities in 14,3%. We could not detect a significant correlation between dental abnormalities and delayed treatment (p > 0,05). DMFT index for 6 to 12 years patients (n = 12) showed that the oral health is unsatisfactory (mean DMFT = 5).

CONCLUSIONS

Patients with Hypophosphatemic Rickets frequently present dental alterations and these are not completely recovered with the treatment, unless dental abscess and they need a periodical oral examination.

Report of a Brazilian multicenter study on nephropathic cystinosis

INTRODUCTION

The Brazilian Multicenter Nephropathic Study Group, founded in 1999, is currently composed of 16 pediatric nephrology units, which are coordinated by the Pediatric Nephrology Unit of Instituto da Criança--HCFMUSP. This Study Group intends to better know our patients, their special characteristics and facilitates the treatment.

OBJECTIVE

To present an update on the demographics of the ongoing study participants with interest on renal function status, response to therapy, and extra-renal complications.

METHODS

Patient recruitment to the study is based on informed consent and has been supported by the Brazilian Society of Nephrology, by the creation of an electronic homepage and by the participation in medical meetings and publications in medical periodicals. Our study protocol involves the initial and follow-up questionnaire, the measurement of intraleukocyte cystine content, initiation and follow-up therapy with cysteamine, and clinical patient follow-up based on a protocol of subsidiary exams.

RESULTS

We identified 102 patients (42 females) with nephropathic cystinosis in Brazil since 1999. Forty-six children are followed at the Instituto da Criança/SP, 15 at the Hospital Pequeno Príncipe/PR, 12 at the UNICAMP/SP, 10 at the Unidade de Transplante Renal - HCFMUSP/SP and 3 at the Santa Casa/SP; the remaining patients are followed at the Instituto da Criança and at their respective doctors' offices in different nephrology services in Brazil. Of these patients, 23/102 (22.5%) have normal renal function, 19/102 (18.6%) are in chronic renal failure with conservative treatment, 26/102 are on dialysis (18 on peritoneal dialysis and 8 on hemodialysis), and 34/102 received a renal transplant. The extra-renal involvement diagnosed was: hypothyroidism in 63 patients, diabetes mellitus in 8 patients, muscular involvement in 7 patients, a compromised central nervous system in 5 patients, hepatic complications in 5 patients, and deglutition dysfunction in 2 patients. During this period, 10/102 patients died. Cysteamine has been used by 81/102 patients (20 children started the therapy under 2 years of age). Growth parameters were improved by cysteamine, mainly in the youngest patients. We used recombinant growth hormone in 15 patients with persistent low growth velocity and stature z score under 2.5%. We could also observe a delay in appearance of extra-renal complications in patients receiving cysteamine.

CONCLUSION

Our study demonstrates the importance of a multi-center study for recruitment, diagnosis and management of rare diseases. This study promotes access to the adequate treatment with profound impact on the quality of life.

Nephrogenic diabetes insipidus (NDI): clinical, laboratory and genetic characterization of five Brazilian patients

INTRODUCTION

Nephrogenic diabetes insipidus is characterized by a lack of response in the distal nephron to the antidiuretic hormone arginine vasopressin. Manifestations include polyuria, polydipsia, hyposthenuria, recurrent episodes of dehydration and fever and growth failure. Most cases are caused by mutations in the AVPR2 gene. The mutant receptors are trapped intracellularly.

METHOD

We studied five boys using clinical, laboratory and molecular data. The mean age at diagnosis was 14.6 months (range 6 to 24) and 12.2 years (7.8 to 19) after the follow-up period. The mean period of follow-up was 132.2 +/- 50.9 months.

RESULTS

The geometric means of the z-scores of weight and stature were -4.5 and -3.6, respectively, at diagnosis. At the last medical appointment, the z-scores of weight and stature were -0.3 and -0.9, respectively. Three patients were diagnosed with ureterohydronephrosis and exhibited increased post-void urine volume. Mutations in the AVPR2 gene were found in all patients, and the carrier status was confirmed in four of five cases. Two unrelated children presented identical mutations (S167L) in arginine vasopressin R2. Two of the patients had a mutation that has already been described in other Brazilian families (R337X), and one patient showed a de novo mutation (Y128D) in arginine vasopressin R2, since his mother's molecular analysis was normal. The recurrence risk for this family was significantly reduced.

CONCLUSION

This study reports the clinical and laboratory characterization of Nephrogenic diabetes insipidus and reiterates the importance of the genetic basis that underlies the disease diagnosis and genetic counseling.

Functional analysis of a novel missense NBC1 mutation and of other mutations causing proximal renal tubular acidosis

Mutations in the Na(+)-HCO(3)(-) cotransporter NBC1 cause severe proximal tubular acidosis (pRTA) associated with ocular abnormalities. Recent studies have suggested that at least some NBC1 mutants show abnormal trafficking in the polarized cells. This study identified a new homozygous NBC1 mutation (G486R) in a patient with severe pRTA. Functional analysis in Xenopus oocytes failed to detect the G486R activity due to poor surface expression. In ECV304 cells, however, G486R showed the efficient membrane expression, and its transport activity corresponded to approximately 50% of wild-type (WT) activity. In Madin-Darby canine kidney (MDCK) cells, G486R was predominantly expressed in the basolateral membrane domain as observed for WT. Among the previously identified NBC1 mutants that showed poor surface expression in oocytes, T485S showed the predominant basolateral expression in MDCK cells. On the other hand, L522P was exclusively retained in the cytoplasm in ECV304 and MDCK cells, and functional analysis in ECV304 cells failed to detect its transport activity. These results indicate that G486R, like T485S, is a partial loss of function mutation without major trafficking abnormalities, while L522P causes the clinical phenotypes mainly through its inability to reach the plasma membranes. Multiple experimental approaches would be required to elucidate potential disease mechanism by NBC1 mutations.

Hypophosphatemic rickets: results of a long-term follow-up

This study reports the benefits and side effects of conventional treatment, phosphate and calcitriol supplementation in patients with heritable hypophosphatemic rickets and a long-term follow-up, median of 60.9 months. The group is composed of 17 patients (ten girls). Sixteen patients presented with bone pain and/or deformities, and in one patient the diagnosis was radiological. All the patients had increased alkaline phosphatase, hypophosphatemia, decreased fractional phosphate tubular reabsorption (TRP) and maximum tubular phosphate reabsorption/glomerular filtration rate ratio (TPO4/GFR). Ten of 17 patients had metabolic acidosis, which was corrected only with the conventional treatment. Potassium citrate was prescribed to the patients who developed hypercalciuria. Excluding one patient with pulmonary dysfunction, the remaining 16 patients were divided into two groups according to the age at treatment onset (T0): group I (GI) > or =4 years (n =9) and GII <4 years (n =7). GI and GII had similar follow-up periods and treatment protocols. Seven out of nine GI patients underwent orthopedic surgery, in contrast to none of GII. Anthropometric data results showed that within each group there is no difference in weight and stature z -score at T0 and at the end of the observation (Tf), but, when both groups are compared, GII shows higher z-score for stature at T0 (p <0.05) and at Tf (p <0.05). Nephrocalcinosis developed in three cases and correlated with hypercalciuria (p <0.001) and dose of calcitriol (p =0.03). In conclusion, higher stature z-score is associated with early treatment. A careful protocol is recommended to detect such complications as nephrocalcinosis. We suggest potassium citrate for patients with hypercalciuria to avoid calcium precipitation.

Bartter syndrome: benefits and side effects of long-term treatment

The present study reports clinical and laboratory data of patients with Bartter syndrome at diagnosis and follow-up with emphasis on the long-term benefits and side effects of the pharmacological therapy, which includes indomethacin and potassium supplementation. We followed 12 children, 6 boys, with a median age at diagnosis of 24.5 months (range 7-137 months) and at the end of the study 157.5 months (range 26.0-224.0 months). All children presented with polyuria and polydipsia, dehydration, and metabolic and electrolyte disturbances with failure to thrive. However, at study entry 5 of 12 patients also had hypophosphatemia, which disappeared after a mean time of 50+/-22.4 months, 3 of 12 had nephrocalcinosis, and 2 of 12 had typical renal cysts. Despite treatment, hypokalemia was persistent in some patients. During long-term follow-up we observed recovery of growth velocity and adequate metabolic and electrolyte balance. However, we noticed renal and gastrointestinal complications: 2 patients had a perforated gastric ulcer, 1 had a gastric ulcer, and gastritis was detected in 3 children. A decreased glomerular filtration rate was observed in 2 patients during follow-up. Our data emphasize the need for regular surveillance of renal function and gastrointestinal endoscopy in these patients. As an alternative to indomethacin, we present our satisfactory preliminary results with rofecoxib.

Fístula gastrocólica na síndrome de Bartter em uso de indometacina: relato de dois casos

Os autores relatam dois casos de fístula gastrocólica causada por uso crônico de indometacina em pacientes com síndrome de Bartter, em acompanhamento no Instituto da Criança do Hospital das Clínicas da Faculdade de Medicina da Universidade de São Paulo. O diagnóstico foi realizado por meio de trânsito intestinal, que evidenciou passagem de contraste da grande curvatura gástrica para o cólon transverso. O tratamento foi cirúrgico em ambos os casos.

[Retinol-binding protein urinary levels in a pediatric population: evolution according to age]

OBJECTIVE: The kidney of the child, mainly the newborn, is specially susceptible to ischemic and/or toxic injuries, which can affect the renal tubular function. Therefore, reliable and precocious markers of tubular dysfunction would be useful in Pediatrics. The urinary levels of retinol binding-protein (RBPu) has been used in this way. Our goal was to evaluate the RBPu behavior in childhood to establish a reference interval and verify possible differences according to the age. METHODS: We studied healthy children aged 1 month to 8 years and healthy term and preterm babies; in the last group we only included babies without hemodynamic repercussion. We collected isolated urine samples once for children above 1 month and periodically for those below this age. In this urine, besides the dipsticks test (Combur 9(R), Boehringer), RBPu and creatinine were measured. RESULTS: We observed that the RBPu levels in childhood do not have a normal distribution; after logarithm data transformation we were able to establish an interval of reference for children above one month of age: 3 to 269 micro g/L, mean of 27 micro g/ L. In newborns, we found a large variation of RBPu excretion. However, we noticed that the excretion decreases significantly, reaching the healthy adult levels at the end of the 1st month, for term as well as for preterm newborns. CONCLUSIONS: We suggest that RBPu can be used as a marker of proximal tubular dysfunction, since we could establish an interval of reference, and it can be repeated whenever necessary in the follow-up of this kind of injury, because it is not an invasive exam. Moreover, this study contributes to the knowledge of the tubular function development for showing that at the end of the 1st month of life the newborn's kidney is able to reabsorb RBPu as the healthy adult kidney is.

[Hematuria in children: retrospective study of 128 pediatric patients]

OBJECTIVE: To evaluate the diagnostic frequency of the various diseases associated with the development of hematuria in children, in a pediatric nephrology unit pertaining to a university hospital. METHODS: The clinical records of 128 children (70 male, 50 female) who presented intermittent/persistent macroscopic hematuria or persistent microscopic hematuria as the chief clinical complaint/finding, in the period of 1978-1995, were retrospectively analyzed. This evaluation was performed with special attention to the patientacute;s clinical history, physical examination, personal and family morbid history information. Patients whose investigation was not complete were not considered for analysis. The mean age on presentation was 8.2 years (5 months - 16 years) and the mean period of observation was 3.2 years (1 month-15 years). RESULTS: Macroscopic hematuria occurred in 104 patients and persistent microscopic hematuria was present in 24 patients. Urinary metabolic disturbances and urinary lithiasis, alone or in association, were diagnosed in the majority of the patients (65.5%). Hypercalciuria was the urinary metabolic disturbance (90.1%) mostly detected, either alone (73.2%) or in association with hyperuricosuria (16.9%). A positive family history of lithiasis was reported in 32.1% of the patients in which the diagnosis of lithiasis/urinary metabolic disturbance was confirmed. Glomerulopathies were diagnosed in 25% of the patients, with the predominance of post-infectious acute glomerulonephritis (11 patients, 34%). In 6 children, the etiology of hematuria was not elucidated, despite extensive investigation, including renal biopsy.CONCLUSION: The authors present an algorithm for the diagnosis of hematuria in children and suggest that in cases of isolated hematuria, presenting without clinical clues to the possible etiology, laboratory investigation should be started with the evaluation of urinary metabolic disturbances / lithiasis.