Multidisciplinary approach to screening and management of children with Fabry disease: practice at a Tertiary Children’s Hospital in China

Background Fabry disease (FD) remains poorly recognized, especially in children in China. Considering the diversity and nonspecific clinical manifestations accompanying with life-threatening aspect of this disease, methods to improve effective screening and management of the suspects are needed. This study aims to explore how it can be done effectively from a multidisciplinary perspective for children with FD at a tertiary children’s hospital in China. Methods A multidisciplinary team (MDT) of pediatric FD experts was launched at Children’s Hospital of Fudan University. Children with high-risk characteristics were referred by the MDT screening team using the dried blood spot (DBS) triple-test (α-galactosidase A, globotriaosylsphingosine, GLA gene). For newborns who were undergoing genetic testing in the hospital, the GLA gene was listed as a routine analysis gene. Evaluation, family screening, and genetic counselling were implemented after screening by the MDT management team. Results Before the establishment of the MDT, no case was diagnosed with FD in the hospital. However, twelve months following the MDT program's implementation, thirty-five children with high-risk profiles were referred for screening by DBS triple-test, with a yield of diagnosis of 14.3% (5/35). These 5 diagnosed children were referred due to a high-risk profile of pain accompanied by dermatological angiokeratoma and hypohidrosis (n = 2), pain accompanied by abnormal liver function (n = 1), pain only (n = 1), and unexplained renal tubular dysfunction (n = 1). Two neonates were detected early with GLA mutations in the hospital, with a yield of detection of 0.14% (2/1420). Furthermore, another 3 children diagnosed with FD were referred from other hospitals. Family screening of these 10 diagnosed children indicated that 9 boys inherited it from their mothers and 1 girl inherited it from her father. Four of them started to receive enzyme replacement therapy. Conclusion Screening and management of children with FD is effective based on a defined screening protocol and a multidisciplinary approach. We should pay more attention to the high-risk profiles of pain, angiokeratoma, decreased sweating, and unexplained chronic kidney disease in children.

β-Thalassemia minor & renal tubular dysfunction: is there any association?

Objective Beta(β)-thalassemia is one of the most common hereditary hematologic disorders. Patients with thalassemia minor (TM) are often asymptomatic and the rate of renal dysfunction is unknown in these patients. Due to the high prevalence of renal dysfunction in Iran, the current study aimed to determine renal tubular dysfunction in patients with beta-TM. Methods In this case-control study, 40 patients with TM and 20 healthy subjects were enrolled and urinary and blood biochemical analysis was done on their samples. Renal tubular function indices were determined and compared in both groups. Data was analyzed by SPSS software, version 20.0. Results The fraction excretion (FE) of uric acid was 8.31 ± 3.98% in the case and 6.2 ± 34.71% in the control group (p = 0.048). Also, FE of potassium was significantly higher in patients with TM (3.22 ± 3.13 vs. 1.91 ± 0.81; p = 0.036). The mean Plasma NGAL level was 133.78 ± 120.28 ng/mL in patients with thalassemia and 84.55 ± 45.50 ng/mL in the control group (p = 0.083). At least one parameter of tubular dysfunction was found in 45% of patients with thalassemia. Conclusion Based on the results of this study, the prevalence of tubular dysfunction in beta-thalassemia minor patients is high. Due to the lack of knowledge of patients about this disorder, periodic evaluation of renal function in TM patients can prevent renal failure by early diagnosis.

Urinary concentrations of neonicotinoid insecticides were related to renal tubular dysfunction and neuropsychological complaints in Dry-zone of Sri Lanka

Neonicotinoids are systemic insecticides used since the 1990’s , that possess renal tubular toxicity. We conducted a field-based descriptive study in the North Central Dry-zone of Sri Lanka, where chronic kidney disease (CKD) of unknown etiology has been increasing since the 1990’s. To elucidate the relationship between renal tubular dysfunctions and urinary neonicotinoids concentrations, we collected spot urine samples from15 CKD patients, 15 family members, and 62 neighbors in 2015, analyzed two renal tubular biomarkers, Cystatin-C and L-FABP, quantified seven neonicotinoids and a metabolite N-desmethyl-acetamiprid by LC–MS/MS; and we investigated their symptoms using a questionnaire. Cystatin-C and L-FABP had a positive correlation (p < 0.001). N-Desmethyl-acetamiprid was detected in 92.4% of the urine samples, followed by dinotefuran (17.4%), thiamethoxam (17.4%), clothianidin (9.8%), thiacloprid and imidacloprid. Dinotefuran and thiacloprid have never been registered in Sri Lanka. In High Cystatin-C group (> 70 μg/gCre, n = 7), higher urinary concentration of dinotefuran (p = 0.009), and in Zero Cystatin-C group (< LOQ, n = 7), higher N-desmethyl-acetamiprid (p = 0.013), dinotefuran (p = 0.049), and thiacloprid (p = 0.035), and more complaints of chest pains, stomachache, skin eruption and diarrhea (p < 0.05) were found than in Normal Cystatin-C group (n = 78). Urinary neonicotinoids may be one of the potential risk factors for renal tubular dysfunction in this area.

Evidence for a Genotype–Phenotype Correlation in Patients with Pathogenic GLUT2 (SLC2A2) Variants

Fanconi-Bickel syndrome (FBS) is a very rare but distinct clinical entity with the combined features of hepatic glycogen storage disease, generalized proximal renal tubular dysfunction with disproportionately severe glucosuria, and impaired galactose tolerance. Here, we report five cases (out of 93 diagnosed in our lab) with pathogenic variants on both GLUT2 (SLC2A2) alleles. They come from 3 families and presented with an exceptionally mild clinical course. This course was correlated to data from old and most recent expression and transport studies in Xenopus oocytes. GLUT2 genotype in patients 1 and 2 was p.[153_4delLI];[P417R] with the first variant exhibiting normal membrane expression and partially retained transport activity (5.8%) for 2-deoxyglucose. In patient 3, the very first GLUT2 variant ever detected (p.V197I) was found, but for the first time it was present in a patient in the homozygous state. This variant had also shown unaffected membrane expression and remarkable residual activity (8%). The genotype in patient 4, p.[153_4delLI];[(E440A)], again included the 2-amino-acid deletion with residual transporter function, and patient 5 is the first found to be homozygous for this variant. Our results provide further evidence for a genotype-phenotype correlation in patients with GLUT2 variants; non-functional variants result in the full picture of FBS while dysfunctional variants may result in milder presentations, even glucosuria only, without other typical signs of FBS.

Tubular Dysfunction and Ruptured Ureter in a Child with Menkes Syndrome

Children with Menkes disease may develop various urological and renal problems that evolve as the disease progresses. A 4-year-old boy with Menkes disease had multiple bladder diverticula and a history of recurrent urinary tract infection caused by urea-splitting organisms. The child developed urosepsis and right pyelonephritis. Subsequent investigations revealed multiple right renal stones and a ruptured right ureter. The child also developed hypokalemia, hypophosphatemia, and normal anion gap metabolic acidosis that required electrolyte and potassium citrate supplement. Further assessment revealed renal tubular dysfunction. Our case suggests that regular imaging surveillance, monitoring of renal function and electrolyte profile, and tubular function assessment should be considered in children with Menkes disease.

Construction of Mode of Action for Cadmium-Induced Renal Tubular Dysfunction Based on a Toxicity Pathway-Oriented Approach

Although it is recognized that cadmium (Cd) causes renal tubular dysfunction, the mechanism of Cd-induced nephrotoxicity is not yet fully understood. Mode of action (MOA) is a developing tool for chemical risk assessment. To establish the mechanistic MOA of Cd-induced renal tubular dysfunction, the Comparative Toxicogenomics Database (CTD) was used to obtain genomics data of Cd-induced nephrotoxicity, and Ingenuity® Pathway Analysis (IPA) software was applied for bioinformatics analysis. Based on the perturbed toxicity pathways during the process of Cd-induced nephrotoxicity, we established the MOA of Cd-induced renal tubular dysfunction and assessed its confidence with the tailored Bradford Hill criteria. Bioinformatics analysis showed that oxidative stress, DNA damage, cell cycle arrest, and cell death were the probable key events (KEs). Assessment of the overall MOA of Cd-induced renal tubular dysfunction indicated a moderate confidence, and there are still some evidence gaps to be filled by rational experimental designs.

Bartter syndrome and hypothyroidism masquerading cystinosis in a 3-year-old girl: rare manifestation of a rare disease

Cystinosis is a multisystem disorder with varied presentations secondary to deposition of cystine crystals in different organ systems. Children with cystinosis typically present with renal tubular acidosis and failure to thrive. We report a 3-year-old girl, born to a third-degree consanguineous couple, who presented with failure to thrive and polyuria. Laboratory investigations showed metabolic alkalosis suggestive of a Bartter-like syndrome and acquired hypothyroidism. Although metabolic alkalosis is a rare manifestation of cystinosis, the presence of renal tubular dysfunction and hypothyroidism prompted consideration of a probable diagnosis of cystinosis in the index child. Slit-lamp examination revealed cystine crystals in the cornea and genetic analysis showed a mutation in exon 9 of the CTNS (cystinosin, lysosomal cystine transporter) gene on chromosome 17. We highlight the importance of considering cystinosis as a differential diagnosis for Bartter syndrome and hypothyroidism.

Current Challenges and Future Perspectives of Renal Tubular Dysfunction in Diabetic Kidney Disease

Over decades, substantial progress has been achieved in understanding the pathogenesis of proteinuria in diabetic kidney disease (DKD), biomarkers for DKD screening, diagnosis, and prognosis, as well as novel hypoglycemia agents in clinical trials, thereby rendering more attention focused on the role of renal tubules in DKD. Previous studies have demonstrated that morphological and functional changes in renal tubules are highly involved in the occurrence and development of DKD. Novel tubular biomarkers have shown some clinical importance. However, there are many challenges to transition into personalized diagnosis and guidance for individual therapy in clinical practice. Large-scale clinical trials suggested the clinical relevance of increased proximal reabsorption and hyperfiltration by sodium-glucose cotransporter-2 (SGLT2) to improve renal outcomes in patients with diabetes, further promoting the emergence of renal tubulocentric research. Therefore, this review summarized the recent progress in the pathophysiology associated with involved mechanisms of renal tubules, potential tubular biomarkers with clinical application, and renal tubular factors in DKD management. The mechanism of kidney protection and impressive results from clinical trials of SGLT2 inhibitors were summarized and discussed, offering a comprehensive update on therapeutic strategies targeting renal tubules.

A Rare Case of Nephrogenic Diabetes Insipidus From Tenofovir

Introduction: Diabetes insipidus (DI) is a clinical condition which manifests as excessive urine output, either because of impaired or inadequate antidiuretic hormone (ADH) secretion, or an inability of the kidneys to respond to ADH. Nephrogenic DI is more often drug induced. Recent clinical reports have shown that medications like tenofovir may result in nephrogenic DI as well. Tenofovir is a well-known nucleoside reverse transcriptase inhibitor analog of adenosine used in the management of both human immunodeficiency virus (HIV) and chronic hepatitis B. With its increased use, reports of adverse outcomes have been documented, mainly its effect on renal function including nephrogenic DI, renal failure and Fanconi syndrome. We present a case of nephrogenic DI whilst on Biktarvy (a combination of bictegravir, emtricitabine and tenofovir alafenamide). Case: A 59-year-old African American female with a history of HIV on Biktarvy, T2DM, HLD, HTN, MI, CAD, COPD presented to our hospital with weakness and falls for 1-2 months associated with polydipsia and polyuria. She had started Biktarvy for HIV about 2 months ago after which her symptoms got worse. Labs showed a serum Na of 151, potassium of 3.2 on admission with serum osmolality of 323 and urine osmolality of 134. During hospitalization, she was challenged with 100ug oral Desmopressin. Urine labs failed to correct after Desmopressin administration which was highly indicative of severe nephrogenic DI. The challenge was repeated with 200ug oral Desmopressin with similar results. Pituitary DI was considered given the patient’s falls; however urine osmolality did not improve following desmopressin challenge. Furthermore, her serum Co-peptin level was elevated at 36.1 that ruled out central DI. The patient’s hypokalemia was believed to be driving her nephrogenic DI which has been reported in various case reports with patients on Tenofovir, but has never been reported in patients taking Biktarvy (which includes Tenofovir Alafenamide). She was subsequently placed on fluid restriction during which time the patient’s serum Na and Cr increased while urine osmolality did not correct. HCTZ was ultimately started as a treatment for nephrogenic DI and patient was transitioned of biktarvy to lamivudine and dolutegravir. Her polyuria and polydipsia improved, however she developed hyponatremia likely because of HCTZ. Patient concentrating ability improved off biktarvy and HCTZ was discontinued on the day prior to discharge without issue. Her subsequent serum sodium and potassium levels were normal. Conclusions: Our case highlights a rare incidence of tenofovir induced hypokalemia leading to nephrogenic DI. This case illustrates the importance of monitoring patients on tenofovir for signs of renal [tubular] dysfunction. In a polyuric patient on tenofovir, there should be a high index of suspicion for nephrogenic diabetes insipidus.