Complicated Gitelman syndrome and autoimmune thyroid disease: a case report with a new homozygous mutation in the SLC12A3 gene and literature review

A novel homozygous SLC12A3 mutation causing Gitelman syndrome with co-existent autoimmune thyroiditis: a case report and review of the literature

Gitelman syndrome is a rare, autosomal recessively inherited tubulopathy manifesting with hypokalemia, hypomagnesemia, hypocalciuria, and metabolic alkalosis. Common symptoms include fatigue, myalgia, reduced performance capacity, tetany, paresthesia, and delayed growth. However, as reported in the literature, diagnosis in some patients is prompted by an incidental finding of hypokalemia. GS develops due to mutations in the SLC12A3 gene, which encodes the thiazide-sensitive Na-Cl cotransporter. Many variants in the SLC12A3 gene causing GS have been reported in literature. A new pathogenic homozygous mutation (c.2612G > T), absence of hypomagnesemia, and accompanying autoimmune thyroiditis are remarkable in our patient. There are a few Gitelman syndrome cases that are complicated with autoimmune thyroiditis in the literature. In this study, we present a case of Gitelman syndrome with a novel homozygous mutation and accompanying autoimmune thyroiditis and review of the literature.

Investigation of Gene Networks in Three Components of Immune System Provides Novel Insights into Immune Response Mechanisms against Edwardsiella tarda Infection in Paralichthys olivaceus

As a quintessential marine teleost, Paralichthys olivaceus demonstrates vulnerability to a range of pathogens. Long-term infection with Edwardsiella tarda significantly inhibits fish growth and even induces death. Gills, blood, and kidneys, pivotal components of the immune system in teleosts, elicit vital regulatory roles in immune response processes including immune cell differentiation, diseased cell clearance, and other immunity-related mechanisms. This study entailed infecting P. olivaceus with E. tarda for 48 h and examining transcriptome data from the three components at 0, 8, and 48 h post-infection employing weighted gene co-expression network analysis (WGCNA) and protein-protein interaction (PPI) network analysis. Network analyses revealed a series of immune response processes after infection and identified multiple key modules and key, core, and hub genes including xpo1, src, tlr13, stat1, and mefv. By innovatively amalgamating WGCNA and PPI network methodologies, our investigation facilitated an in-depth examination of immune response mechanisms within three significant P. olivaceus components post-E. tarda infection. Our results provided valuable genetic resources for understanding immunity in P. olivaceus immune-related components and assisted us in further exploring the molecular mechanisms of E. tarda infection in teleosts.

Gitelman syndrome with Graves' disease leading to rhabdomyolysis: a case report and literature review

A 14-year-old male patient who suffered from limb numbness, fatigue, and hypokalemia was considered Graves' disease (GD) complicated with thyrotoxic periodic paralysis (TPP) at the first diagnosis. Although with the treatment of antithyroid drugs, he developed severe hypokalemia and rhabdomyolysis (RM). Further laboratory tests revealed hypomagnesemia, hypocalciuria, metabolic alkalosis, hyperrenin, and hyperaldosteronemia. Genetic testing revealed compound heterozygous mutations in the SLC12A3 gene (c.506-1G > A, c.1456G > A) encoding the thiazide-sensitive sodium-chloride cotransporter, which presented a definitive diagnosis of Gitelman syndrome (GS). Moreover, gene analysis revealed his mother diagnosed with subclinical hypothyroidism due to Hashimoto's thyroiditis carried the c.506-1G > A heterozygous mutation in the SLC12A3 gene and his father carried the c.1456G > A heterozygous mutation in the SLC12A3 gene. His younger sister who had hypokalemia and hypomagnesemia carried the same compound heterozygous mutations as the proband and was diagnosed with GS as well, but with a much milder clinical presentation and better treatment outcome. This case suggested the potential relationship between GS and GD, clinicians should strengthen the differential diagnosis to avoid missed diagnosis.

A triple SLC12A3 heterozygous mutations in Gitelman syndrome with renal calculi

Background

Gitelman syndrome (GS) is a rare autosomal recessive salt-losing tubulopathy. Mutations in the SLC12A3 gene encoding the renal thiazide-sensitive Na/Cl cotransporter in the distal renal tubule, cause GS. Identifying biallelic inactivating mutations in the SLC12A3 gene is the most common finding in GS, while the detection of renal calculi is relatively rare.

Case presentation

We report the case of a 33-year-old man admitted with recurrent limb weakness for six years. Laboratory tests showed hypokalemic alkalosis, hypocalciuria and renal potassium wasting; serum magnesium and aldosterone were normal, and ultrasound and computed tomography scans showed right-sided renal calculus. A hydrochlorothiazide test was performed, which showed a blunted response to hydrochlorothiazide. Next-generation sequencing identified triple mutations in SLC12A3, including novel splicing heterozygous mutations (c.2285+2T>C). He was administered with oral potassium chloride and spironolactone and maintained mild symptomatic hypokalemia during his follow-up.

Conclusions

The patient was diagnosed with Gitelman syndrome by genetic testing, accompanied by kidney stones. Although kidney stones are rare in Gitelman syndrome, they are not excluded as a criterion. The composition of kidney stones may be of significance for diagnosis and treatment. HIPPOKRATIA 2023, 27 (2):64-68.

Cathepsin F genetic mutation is associated with familial papillary thyroid cancer

BACKGROUND

Thyroid cancer is one of the most common cancers in the world. Genetic factors are important in the occurrence and development of thyroid cancer, and genetic diagnosis has become an important basis for the prognosis of benign and malignant nodules. We identify a family of six siblings with inherited thyroid cancer susceptibility. All six members of this generation have been definitely diagnosed with papillary thyroid carcinoma. This work aims at confirming the relevant causative genes for thyroid cancer in this pedigree.

METHODS

We extract DNA from the peripheral blood of six individuals and perform whole genome sequencing. Sanger sequencing and immunohistochemistry further testify the cathepsin F (CTSF) mutation and expression.

RESULTS

We identify 57 single nucleotide variations (SNVs) out of at least 4 affected family members via certain filter criteria. The CTSF gene found in five of the six family members is here considered the most promising candidate gene mutation for familial thyroid cancer. Besides, our research also proves several known genes including CTSB, TEKT4, ESR1, MSH6, DIRC3, GNAS, and BANCR that act as probable oncogenic drivers in this family. The Sanger sequencing identifies the existence and veracity of CTSF somatic mutations. The CTSF immunohistochemistry of thyroid cancer tissue specimens displays that higher CTSF expression in mutated patients than that in wild-type patient as well as pericarcinomatous tissue.

CONCLUSIONS

We conclude that the evaluation of CTSF gene mutations of patients in thyroid cancer families may be predictive and valuable for the familial heredity of thyroid cancer.

Novel compound heterozygous mutation of SLC12A3 in Gitelman syndrome co-existent with hyperthyroidism: A case report and literature review

BACKGROUND

Gitelman syndrome (GS) is a rare inherited autosomal recessive tubulopathy, characterized clinically by hypokalemia, hypomagnesemia, hypocalciuria, and metabolic alkalosis, and is caused by an inactivating mutation in SLC12A3. GS is prone to misdiagnosis when occurring simultaneously with hyperthyroidism. It is important to consider the possibility of other diseases when hyperthyroidism is combined with hypokalemia, which is difficult to correct.

CASE SUMMARY

A female patient with hyperthyroidism complicated with limb weakness was diagnosed with thyrotoxic hypokalemic periodic paralysis for 4 mo. However, the patient’s serum potassium level remained low despite sufficient potassium replacement and remission of hyperthyroidism. GS was confirmed by whole exome and Sanger sequencing. Gene sequencing revealed compound heterozygous mutations of c.488C>T (p.Thr163Met), c.2612G>A (p.Arg871His), and c.1171_1178dupGCCACCAT (p.Ile393fs) in SLC12A3. Protein molecular modeling was performed to predict the effects of the identified missense mutations. All three mutations cause changes in protein structure and may result in abnormal protein function. All previously reported cases of GS coexisting with autoimmune thyroid disease are reviewed.

CONCLUSION

We have identified a novel compound heterozygous mutation in SLC12A3. The present study provides new genetic evidence for GS.

A novel mutation of SLC12A3 gene causing Gitelman syndrome

A 48-year-old patient with a history of diabetes mellitus, presented to a surgical ward with abdominal pain. She was found to have hypokalemia. Her younger sister had passed away due to sudden cardiac death at the age of 25 years. Further evaluation revealed an elevated trans-tubular potassium gradient suggestive of renal potassium loss, normal blood pressure, hypomagnesemia, hypocalciuria, and alkalosis. Moreover, there was evidence of secondary hyperaldosteronism. Genetic studies revealed two heterozygous mutations of the SLC12A3 gene, including a novel mutation which has not been reported before anywhere in the world. She was treated with intravenous potassium supplementation and was later converted to oral potassium and oral magnesium supplementation with spironolactone. Her potassium and magnesium levels normalized and glycaemic control also improved. Hypokalemia and hypomagnesemia found in Gitelman syndrome may be associated with insulin resistance and correction of electrolytes can lead to better glycaemic control.

Concurrent gitelman syndrome-like tubulopathy and grave's disease

Gitelman syndrome (GS) is a rare autosomal recessive disorder characterized by the loss of function mutation of the solute carrier family-12 member-3 (SLC12A3) gene, encoding for sodium-chloride cotransporter of the distal convolute tubule. GS is characterized by hypokalemia, hypomagnesemia, metabolic alkalosis, and hypocalciuria. GS-like syndrome has been described rarely. Hyperthyroidism due to Grave's disease (GD) is characterized by the presence of autoantibodies to thyrotropin receptors. Concurrent occurrence of GS and GD is rarely reported, that too exclusively from far-east Asian populations. We describe a case of a 45-year-old man who presented with severe muscle weakness; the evaluation showed volume depletion, hypokalemia, hypomagnesemia, renal potassium and magnesium wasting, metabolic alkalosis, and hypocalciuria. He was also detected to have GD at the time of presentation. Genetic evaluation revealed a mutation in transient receptor potential melastatin 4 (TRPM4) gene. The clinical significance of this mutation in our patient remains unclear.

Unmasking of Gitelman Syndrome during Pregnancy in an Adolescent with Thyrotoxic Crisis

BACKGROUND

Gitelman syndrome (GS) is an inherited salt-losing renal tubulopathy characterized by hypokalemic metabolic alkalosis with hypomagnesemia and hypocalciuria. Patients can be asymptomatic until late adolescence or adulthood, and hence may be discovered incidentally during presentation with other illnesses. GS has been described in association with thyroid disorders and should be considered in patients with hyperthyroidism and persistent hypokalemia, especially in those with associated hypomagnesemia and hypocalciuria.

CASE SUMMARY

In this report, we describe an 18-year-old female who presented with hyperemesis gravidarum and thyrotoxicosis, and was incidentally found to have GS, confirmed by the sequence analysis of SLC12A3. Conclusions. Thyroid dysfunctions, such as hypothyroidism, thyrotoxicosis, and thyroid nodules, may develop during pregnancy. A structural homology between the beta-human chorionic gonadotropin and thyroid stimulating hormone molecules, as well as their receptors is probably the basis for the transient thyrotoxicosis crisis during pregnancy. Since hyperemesis in pregnancy can also lead to hypokalemia and alkalosis, a high index of suspicion for GS during pregnancy is required for timely diagnosis and management.

Novel mutations of the SLC12A3 gene in patients with Gitelman syndrome

Mutations in the SLC12A3 gene have been reported to cause Gitelman syndrome (GS). This study aimed to investigate the genetic mutations and clinical features of patients with GS. Four pedigrees (4 GS patients and 14 family members) were enrolled. The symptoms, laboratory results, management, and genotypes were analyzed. Genomic DNA was screened for gene variations using Sanger sequencing. DNA sequences were compared with reference sequences. The effects of the mutations were predicted using prediction tools (Mutation Taster, PolyPhen-2, SIFT, and PROVEAN). Genetic analysis revealed six genetic variants of SLC12A3, including three novel heterozygous mutations (c.2T > C, c.1609C > T, c.3055G > A) and three previously characterized mutations (c.1456G > A, c.2542G > A, c.1077C > G). These mutations were predicted to exert a damaging effect based on predictive in silico tools. GS patients had low blood pressure and low levels of serum K⁺, serum Mg²⁺, and 24-h urinary Ca²⁺ but high levels of 24-h urinary K⁺. These clinical manifestations and genotypes were consistent with the diagnostic criteria of GS. The study described the phenotypes and genotypes of 4 pedigrees involving GS patients, demonstrating the importance of SLC12A3 gene screening for GS.

Review and Analysis of Two Gitelman Syndrome Pedigrees Complicated with Proteinuria or Hashimoto's Thyroiditis Caused by Compound Heterozygous SLC12A3 Mutations

Gitelman syndrome (GS) is an autosomal recessive inherited salt-losing renal tubular disease, which is caused by a pathogenic mutation of SLC12A3 encoding thiazide-sensitive Na-Cl cotransporter, which leads to disturbance of sodium and chlorine reabsorption in renal distal convoluted tubules, resulting in phenotypes such as hypovolemia, renin angiotensin aldosterone system (RAAS) activation, hypokalemia, and metabolic alkalosis. In this study, two GS families with proteinuria or Hashimoto's thyroiditis were analyzed for genetic-phenotypic association. Sanger sequencing revealed that two probands carried SLC12A3 compound heterozygous mutations, and proband A carried two pathogenic mutations: missense mutation Arg83Gln, splicing mutation, or frameshift mutation NC_000016.10:g.56872655_56872667 (gcggacatttttg>accgaaaatttt) in exon 8. Proband B carries two missense mutations: novel Asp839Val and Arg904Gln. Both probands manifested hypokalemia, hypomagnesemia, hypocalcinuria, metabolic alkalosis, and RAAS activation; in addition, the proband A exhibited decreased urinary chloride, phosphorus, and increased magnesium ions excretion, complicated with Hashimoto's Thyroiditis, while the proband B exhibited enhanced urine sodium excretion and proteinuria. The older sister of proband B with GS also had Hashimoto's thyroiditis. Electron microscopy revealed swelling and vacuolar degeneration of glomerular epithelial cells, diffuse proliferation of mesangial cells and matrix, accompanied by a small amount of low-density electron-dense deposition, and segmental fusion of epithelial cell foot processes in proband B. Light microscopy showed mild mesangial hyperplasia in the focal segment of the glomerulus, hyperplasia, and hypertrophy of juxtaglomerular apparatus cells, mild renal tubulointerstitial lesions, and one glomerular sclerosis. So, long-term hypokalemia of GS can cause kidney damage and may also be susceptible to thyroid disease.

A novel homozygous mutation (p.N958K) of SLC12A3 in Gitelman syndrome is associated with endoplasmic reticulum stress

PURPOSE

Gitelman syndrome (GS) is an autosomal recessive renal tubular disease that arises as a consequence of mutations in the SLC12A3 gene, which codes for an Na-Cl cotransporter (NCC) in distal renal tubules. This study was designed to explore the mutations associated with GS in an effort to more fully understand the molecular mechanisms governing GS.

METHODS

We analyzed SLC12A3 mutations in a pedigree including a 42-year-old male with GS as well as four related family members over three generations using Sanger and next generation sequencing approaches. We additionally explored the functional ramifications of identified mutations using both Xenopus oocytes and the HEK293T cell line.

RESULTS

We found that the subject with GS exhibited characteristic symptoms including sporadic thirst, fatigue, excess urination, and substantial hypokalemia and hypocalciuria, although magnesium levels were normal. Other analyzed subjects in this pedigree had normal laboratory findings and did not exhibit clear signs of GS. Sequencing analyses revealed that the GS subject exhibited a homozygous missense mutation (c.2874C > G, p.N958K) in exon 24 of SLC12A3. Both parents of this GS subject, as well as his older brother and daughter all exhibited heterozygous mutations at this same site. Functional analyses in Xenopus oocytes indicated that this mutated SLC12A3 gene encodes a protein which fails to mediate normal sodium transport, and when this mutant gene was expressed in HEK293T cells, we observed significant increases in endoplasmic reticulum (ER)-stress pathway activation.

CONCLUSION

The p.N958K mutation in exon 24 of SLC12A3 can trigger GS at least in part via enhancing ER stress responses.

Hypokalemic paralysis in hyperthyroidism: Not all that glitter are gold

Abnormal acid-base status (metabolic acidosis or alkalosis), inappropriate urine electrolytes excretion (high or low Na+ and Cl-), and higher required dose of potassium supplement (4-5 mmol/kg) are suggestive of non-TPP causes of hypokalemia.

Thyroid Function in 35 Patients with Gitelman Syndrome

Objective. In this study, we aimed to analyze thyroid function and related risk factors for thyroid dysfunction in 35 patients with Gitelman syndrome (GS). Methods. This study included 35 patients with GS who were referred to West China Hospital of Sichuan University from Aug 2013 to Jan 2018. General patient characteristics were collected, and thyroid function was assessed. To evaluate the potential contribution of hypokalemia to thyroid dysfunction, 636 patients who were clinically diagnosed with primary aldosteronism (PA) during the same period were included as the control group; these patients were divided into a hypokalemia group ( $N=528$ ) and a normokalemia group ( $N=108$ ). Logistic regression was used to screen for significant determinants of thyroid dysfunction in the GS patients. Results. Patients with GS had a significantly different prevalence of subclinical hypothyroidism, hypothyroidism, and hyperthyroidism than patients with hypokalemic PA and normokalemic PA (28.6%, 2.9%, and 11.4% vs. 15.5%, 6.1%, and 0.7% vs. 8.3%, 4.6%, and 2.8%, $P<0.001$ ). No significant difference was observed in the distribution of thyroid function between the hypokalemic PA group and the normokalemic PA group ( $P>0.05$ ). No significant differences were seen in the positive rates of thyrotropin receptor antibody (TRAb), thyroglobulin antibody (TGAb), and thyroid peroxidase antibody (TPOAb) among the three groups ( $P>0.05$ ). In the logistic regression, only sex (OR, 7.4; 95% CI, 1.555-35.479; $P=0.012$ ) was significantly correlated with thyroid dysfunction in GS patients. Conclusion. GS is complicated with a greater rate of thyroid dysfunction than primary aldosteronism. The risk of thyroid dysfunction in female patients with GS is higher than that in male patients.

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.

Inherited salt-losing tubulopathies are associated with immunodeficiency due to impaired IL-17 responses

Increased extracellular sodium activates Th17 cells, which provide protection from bacterial and fungal infections. Whilst high salt diets have been shown to worsen autoimmune disease, the immunological consequences of clinical salt depletion are unknown. Here, we investigate immunity in patients with inherited salt-losing tubulopathies (SLT). Forty-seven genotyped SLT patients (with Bartter, Gitelman or EAST Syndromes) are recruited. Clinical features of dysregulated immunity are recorded with a standardised questionnaire and immunological investigations of IL-17 responsiveness undertaken. The effects of altering extracellular ionic concentrations on immune responses are then assessed. Patients are hypokalaemic and hypomagnesaemic, with reduced interstitial sodium stores determined by ²³Na-magnetic resonance imaging. SLT patients report increased mucosal infections and allergic disease compared to age-matched controls. Aligned with their clinical phenotype, SLT patients have an increased ratio of Th2:Th17 cells. SLT Th17 and Tc17 polarisation is reduced in vitro, yet STAT1 and STAT3 phosphorylation and calcium flux following T cell activation are unaffected. In control cells, the addition of extracellular sodium (+40 mM), potassium (+2 mM), or magnesium (+1 mM) reduces Th2:Th17 ratio and augments Th17 polarisation. Our results thus show that the ionic environment typical in SLT impairs IL-17 immunity, but the intracellular pathways that mediate salt-driven Th17 polarisation are intact and in vitro IL-17 responses can be reinvigorated by increasing extracellular sodium concentration. Whether better correction of extracellular ions can rescue the immunophenotype in vivo in SLT patients remains unknown.

Salt levels in culture affect the polarisation of Th17 cells, which normally protect the host from fungal and bacterial infections. Here, the authors study patients with salt-losing tubulopathies (SLT) to find that, while Th17 immunity is dampened in SLT patients, their Th17-inducing signaling pathways are intact and can be reinvigorated by exogenous salt.

Interpreting an apoptotic corpse as anti-inflammatory involves a chloride sensing pathway

Apoptotic cell clearance (efferocytosis) elicits an anti-inflammatory response by phagocytes, but the mechanisms that underlie this response are still being defined. Here, we uncover a chloride-sensing signalling pathway that controls both the phagocyte 'appetite' and its anti-inflammatory response. Efferocytosis transcriptionally altered the genes that encode the solute carrier (SLC) proteins SLC12A2 and SLC12A4. Interfering with SLC12A2 expression or function resulted in a significant increase in apoptotic corpse uptake per phagocyte, whereas the loss of SLC12A4 inhibited corpse uptake. In SLC12A2-deficient phagocytes, the canonical anti-inflammatory program was replaced by pro-inflammatory and oxidative-stress-associated gene programs. This 'switch' to pro-inflammatory sensing of apoptotic cells resulted from the disruption of the chloride-sensing pathway (and not due to corpse overload or poor degradation), including the chloride-sensing kinases WNK1, OSR1 and SPAK-which function upstream of SLC12A2-had a similar effect on efferocytosis. Collectively, the WNK1-OSR1-SPAK-SLC12A2/SLC12A4 chloride-sensing pathway and chloride flux in phagocytes are key modifiers of the manner in which phagocytes interpret the engulfed apoptotic corpse.

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.