Hypokalemia, hypomagnesemia, hypocalciuria, and recurrent tetany: Gitelman syndrome in a Chinese pedigree and literature review

Diagnosis and outpatient management of Gitelman syndrome from the first trimester of pregnancy

A 32-year-old woman presented with an incidental finding of hypokalaemia on routine bloods at 9 weeks of a second pregnancy, on a background of lifelong salt craving. Her previous pregnancy was uncomplicated. She had no previous significant medical or family history. Venous blood gases showed a hypokalaemic, normochloraemic metabolic alkalosis. Urinary potassium was elevated. Escalating doses of oral supplementation of potassium, magnesium, sodium and potassium-sparing diuretics were required through the course of pregnancy, in response to regular electrolyte monitoring. These were later weaned and completely stopped post partum. Delivery was uneventful with no maternal or neonatal complications. Genetic testing performed post partum showed heterogenous mutation of SCL12A3 gene.

Clinical Characteristics and Gene Mutation Analysis of the Chinese Han Population with Gitelman Syndrome: 3 Case Reports and a Literature Review

The present study reported clinical characteristics and the results of gene mutation analysis of 3 Chinese patients with Gitelman syndrome (GS). Three patients manifested with normal blood pressure, recurrent hypokalemia, and metabolic alkalosis. Only case 2 had obvious hypomagnesemia. Gene sequencing showed a compound heterozygous mutation in SCL12A3 in case 1 and a homozygous mutation in SCL12A3 in case 2. Heterozygous mutations in SCL12A3 and CLCNKB were found in case 3. Then, the literature was reviewed. The keyword “Gitelman syndrome” was inputted into the PubMed, Wanfang Database, and CNK to search all Chinese patients with GS diagnosed by gene mutations and to extract complete clinical data from December 1998 to 2018. Finally, a total of 124 cases of GS were included. No significant differences in the levels of serum potassium and magnesium were observed among the different gene mutations, and the serum magnesium levels in adults were lower than those of the juvenile. GS with reduced blood magnesium had a serious clinical phenotype. Therefore, GS had a diverse phenotype, and its final diagnosis required genetic profiling. The relationship of gene mutation and clinical phenotype needed further study.

A novel compound heterozygous mutation of SLC12A3 gene in a pedigree with Gitelman syndrome and literature review

BACKGROUND

Gitelman syndrome (GS) is a tubulopathy characterized by hypokalemia, hypomagnesemia, hypocalciuria and metabolic alkalosis, which is caused by mutations in SLC12A3 gene.

OBJECTIVE

The objective of this study was to investigate the mutation of SLC12A3 gene in a pedigree with GS and analyzed the clinical manifestations.

METHODS

Next-generation sequencing and Sanger sequencing were performed to explore the mutations of SLC12A3 gene in a GS pedigree that included a 59-year-old male GS patient and a total of 11 family members within three generations.

RESULTS

A novel compound heterozygous mutation of SLC12A3 gene (c.1712T > C in exon14 and c.2986_2987ins GCT in exon26) was identified by genetic testing in the proband. Moreover, we demonstrated that two brothers shared the same heterozygous mutation with the proband, but only one brother had the GS related symptoms. His nephew was the carrier of one mutation (c.1712T > C), and one of his brother, his sister and niece were carriers of the other (c.2986_2987ins GCT).

CONCLUSIONS

This is the first study to report the novel pathogenic compound heterozygous mutation of SLC12A3 gene in GS. Our result further supports the lack of phenotype-genotype correlations in GS. Further functional studies are required to investigate pathophysiologic mechanisms of GS.

Genetic Analysis of SLC12A3 Gene in Chinese Patients with Gitelman Syndrome

Background

The incidence of Gitelman syndrome (GS) has been increasing in our hospital. The aim of this study was to explore the diagnostic accuracy and features of SLC12A3 gene in Chinese patients with GS.

Material/Methods

We searched the literature about Chinese patients with GS in the PubMed database up to July 2018 and also included 8 GS Chinese patients from our hospital in our analysis that explored the features of SLC12A3 gene. We divided all the patients into 3 groups according to diagnostic consensus. Complete compliance was defined to mean containing 2 allelic mutations, partial compliance to mean one allelic mutation, and clinical compliance to mean no mutations.

Results

Totally, 137 patients were enrolled in this study and 90 mutations were counted. Missense mutations accounted for over 72% in Chinese GS patients and the most common one was Thr60Met. According to the consensus, there were 102 patients (74.5%) in the complete compliance group, 31 patients (22.6%) in the partial compliance group, and only 4 patients (2.9%) in the clinical compliance group.

Conclusions

The SLC12A3 gene analysis in Chinese GS patients revealed that the most common mutation was Thr60Met, one of the missense mutations. Most of the patients were in the complete compliance group (i.e., 2 allelic mutations); the other cases might be explained by gene rearrangement.

Novel heterozygous missense mutation of SLC12A3 gene in Gitelman syndrome: A case report

BACKGROUND

To screen for possible pathogenic loci in a patient with Gitelman syndrome by high-throughput exome sequencing and to explore the relationship between genotype and phenotype.

CASE SUMMARY

The clinical data of the patient were collected. Peripheral blood samples were obtained to isolate white blood cells and extract genomic DNA. High-throughput whole exome sequencing for candidate pathogenic genes in the proband was completed by the Huada Gene Technology Co. Ltd (Shenzhen, China). Sequencing showed a novel heterozygous missense mutation (a G to A transition at nucleotide 2582) in exon 22 of the SLC12A3 gene, which resulted in a substitution of histidine for arginine at position 816 of the LRP1B protein and caused the occurrence of disease.

CONCLUSION

This is the first report of a new pathogenic mutation in SLC12A3. Further functional studies are particularly necessary to explore potential molecular mechanisms.

Gitelman syndrome and primary hyperparathyroidism: a rare association

Gitelman syndrome(GS) is a rare autosomal recessive salt-losing tubulopathy of young adults, characterised by hypokalaemia, hypomagnesaemia, hypocalciuria and secondary hyperaldosteronism. Hypercalcaemia due to hypocalciuria in these patients is extremely rare.A 25-year-old healthy woman was referred to the Endocrinology clinic for evaluation of persistent hypokalaemia. She presented with fatigue, myalgias, cramps and paraesthesia. Her physical examination was normal. Laboratory workup revealed: K⁺ 2.7 mEq/L (r.v.3.5-5.1), 24 hours urinary K⁺ 84.7 mEq/24 hours (r.v.25-125), Mg²⁺ 0.71 mg/dL (r.v.1.6-2.6), 24 hours urinary Mg²⁺ 143.1 mg/24 hours (r.v.73-122), Ca²⁺ 12 mg/dL (r.v.8.4-10.2), aldosterone 47.1 ng/mL (r.v. 4-31) and active renin 374.7 uUI/mL (r.v.4.4-46.1). She was diagnosed with GS and was treated with spironolactone, oral K⁺ and Mg²⁺ supplementation. Further investigation confirmed hypercalcaemia due to primary hyperparathyroidism owing to a single parathyroid adenoma. Following parathyroidectomy serum calcium normalised.Current knowledge favours that hypomagnesaemia in patients with GS protects them from hypercalcaemia. In this context of multiple electrolyte imbalances, correction of hypomagnesaemia is a challenge and should be done carefully. Like in our patient, aetiology of hypercalcaemia should be promptly diagnosed and reversed.