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Kidney Week

Abstract: FR-PO604

Clinical Features and Genotype-Phenotype Correlation of Bartter Syndrome Type 1 and 2

Session Information

Category: Genetic Diseases of the Kidneys

  • 1202 Genetic Diseases of the Kidneys: Non-Cystic

Authors

  • Kondo, Atsushi, Kobe Daigaku, Kobe, Hyogo, Japan
  • Inoki, Yuta, Kobe Daigaku, Kobe, Hyogo, Japan
  • Ichikawa, Yuta, Kobe Daigaku, Kobe, Hyogo, Japan
  • Tanaka, Yu, Kobe Daigaku, Kobe, Hyogo, Japan
  • Kitakado, Hideaki, Kobe Daigaku, Kobe, Hyogo, Japan
  • Ueda, Chika, Kobe Daigaku, Kobe, Hyogo, Japan
  • Ishiko, Shinya, Kobe Daigaku, Kobe, Hyogo, Japan
  • Sakakibara, Nana, Kobe Daigaku, Kobe, Hyogo, Japan
  • Horinouchi, Tomoko, Kobe Daigaku, Kobe, Hyogo, Japan
  • Yamamura, Tomohiko, Kobe Daigaku, Kobe, Hyogo, Japan
  • Iijima, Kazumoto, Hyogo Prefectural Kobe Children’s Hospital, Kobe, Japan
  • Nozu, Kandai, Kobe Daigaku, Kobe, Hyogo, Japan
Background

Bartter syndrome type 1 and 2 (T1/T2BS) are autosomal recessive hereditary salt-losing tubulopathy (SLT) caused by loss-of-function variants of SLC12A1 (NM_000339) and KCNJ1 (NM_000220) respectively. Although the typical case of both diseases presents severe clinical manifestation at the perinatal period, they are very rare diseases and there are few reports on their clinical course and genotype-phenotype correlations.

Methods

Of 651 patients with suspected SLT who underwent comprehensive genetic testing of 124 genes related to the renal disease by next-generation sequencing at our department, T1BS: 16 and T2BS: 10 cases genetically diagnosed were evaluated retrospectively.

Results

In T1BS, 23 variants (novel:15) were found in the SLC12A1, and in T2BS, 11 variants (novel:7) were identified in the KCNJ1.The median age at the time of genetic testing was 0 years for both diseases. The mean serum potassium level at diagnosis was 2.9 mEq/L in T1BS, but all T2BS patients showed transient hyperkalemia (mean 7.5 mEq/L) in the early postnatal period, followed by hypokalemia (mean 3.2 mEq/L). All patients with T1BS required continuous treatment with potassium products, potassium-retaining diuretics, and/or NSAIDs as a treatment for hypokalemia, whereas only 5 patients (50%) with T2BS required these treatments. Concerning renal prognosis, 3 patients with T1BS and 5 patients with T2BS had deteriorated renal function at the time of genetic testing. Regarding the genotype-phenotype correlation, some of the missense variants of both T1 and T2BS did not show polyhydramnios and presented an atypical mild clinical manifestation without any symptoms in neonatal age. As for the KCNJ1 gene, serum potassium levels tended to be high (mean 3.3 mEq/L) in patients with the large deletion variant including the promoter region that has been previously reported, and this variant may present with mild manifestation.

Conclusion

T2BS shows significant hyperkalemia in the early postnatal period, but the severity of hypokalemia after infancy is milder than that of T1BS, and some cases did not require potassium supplementation. The correlation between the genotype-phenotype is not yet clear, but there were some clinically atypical cases, and further research is needed.

Funding

  • Government Support – Non-U.S.