Clinical Course and Prognosis of Tubulopathies Characterized by Metabolic Alkalosis in Children.

OBJECTIVE: Bartter syndrome and Gitelman syndrome are rare inherited tubulopathies characterized by hypokalemic, hypochloremic metabolic alkalosis. This study aimed to clarify the frequency of the phenotypic and genotypic subgroups, clinical features, long-term management, and prognosis of children diagnosed with Bartter syndrome and Gitelman syndrome in this study. MATERIALS AND METHODS: Twenty-seven patients with Bartter syndrome and 6 patients with Gitelman syndrome, who were followed up between 2004 and 2020 in a single center, were included in the study. RESULTS: The median age of diagnosis was 4 months in patients with Bartter syndrome and 174 months in patients with Gitelman syndrome. At the last follow-up, a total of 12 Bartter syndrome patients had chronic kidney disease with a mean 7.79 ± 4.73 years of age; 5 (18.5%) of these patients had chronic kidney disease stage 2, 5 (18.5%) had chronic kidney disease stage 3, and 2 (7.4%) had chronic kidney disease stage 5. Of the 5 patients with Bartter syndrome with chronic kidney disease stage 2, 2 had CLCNKB and 1 had SLC12A1 gene mutation. Also, CLCNKB mutation was detected in 2 of 5 patients with Bartter syndrome with chronic kidney disease stage 3. Finally, 2 patients with Bartter syndrome with chronic kidney disease stage 5 had BSND mutation in one and CLCNKB mutation in the other. Estimated glomerular filtration rates of all patients with Gitelman syndrome were normal at the last follow-up. There was no statistically significant association of development of chronic kidney disease with genetic mutation, nephrocalcinosis, prematurity, and hypokalemia. CONCLUSION: Patients with Bartter syndrome and Gitelman syndrome may have a different clinical course due to the underlying genetic mutation. Bartter syndrome and Gitelman syndrome require lifelong treatment, and regular follow-up is important to prevent advanced-stage chronic kidney disease.

More than tubular dysfunction: cystinosis and kidney outcomes.

BACKGROUND: Cystinosis is a lysosomal storage disease that affects many tissues. Its prognosis depends predominantly on kidney involvement. Cystinosis has three clinical forms: nephropathic infantile, nephropathic juvenile and non-nephropathic adult. Proximal tubular dysfunction is prominent in the infantile form, whereas a combination of glomerular and tubular alterations are observed in the juvenile form. METHODS: Thirty-six children with nephropathic cystinosis were included in the study. Clinical features, molecular genetic diagnoses, and kidney outcomes of the patients were evaluated. RESULTS: Twenty-one children (58.3%) were male. The median age at diagnosis was 18.5 months. Twenty-eight patients (77.8%) had infantile nephropathic cystinosis, while eight (22.2%) had juvenile nephropathic cystinosis. An acute rapid deterioration of the kidney function with proteinuria, hypoalbuminemia, and nephrotic syndrome, was observed in 37.5% of patients with the juvenile form. The mean estimated glomerular filtration rate (eGFR) was 82.31 ± 37.45 ml/min/1.73m2 at diagnosis and 63.10 ± 54.60 ml/min/1.73m2 at the last visit (p = 0.01). Six patients (16.6%) had kidney replacement therapy (KRT) at the last visit. The median age of patients with kidney failure was 122 months. Patients with a spot urine protein/creatinine ratio < 6 mg/mg at the time of diagnosis had better kidney outcomes (p = 0.01). The most common allele was c.451A>G (32.6%). The patients with the most common mutation tended to have higher mean eGFR and lower leukocyte cystine levels than patients with other mutations. CONCLUSION: Glomerulonephritis may be a frequent finding in addition to the well-known tubular dysfunction in patients with cystinosis. Furthermore, our results highlight that the presence of severe proteinuria at the time of diagnosis is a relevant prognostic factor for kidney survival.

Evaluation of phenotypic and genotypic features of children with distal kidney tubular acidosis.

BACKGROUND: The present study aimed to assess genotype-phenotype correlations with long-term prognosis in children with distal kidney tubular acidosis (dKTA). The kidney function of children with dKTA could be impaired in the long-term. METHODS: Thirty-one children with dKTA from 23 families were included in the present study. Demographic features, growth parameters, clinical manifestations, follow-up results, and genetic analysis results of the patients were recorded. RESULTS: Eighteen children (58.1%) were male. The median age at diagnosis was 3 months. The median follow-up period was 77 months and the longest was 23.5 years. Eight (28.8%) patients had chronic kidney disease (CKD) stage 2 or 3. Three patients aged 24, 23, and 19 years had CKD stage 3 with an estimated glomerular filtration rate of 54, 57, and 48 mL/min/1.73 m2, respectively. Thirteen patients had mutations in the ATP6V0A4 gene, eight had mutations in the ATP6V1B1 gene, and three had mutations in the SLC4A1 gene. There was no significant correlation between molecular diagnosis and CKD. Growth retardation with a height below a standard deviation (SD) score of - 2 was found in 14 patients (45.1%) at the time of diagnosis. The mean height SD score at the last visit was significantly higher in patients who had adequate metabolic control at > 75% of all visits as compared with that in patients who did not. CONCLUSION: Patients with dKTA usually have a good clinical prognosis in childhood with appropriate treatment; however, dRTA is characterized by deterioration of kidney function in adulthood, particularly after puberty.