Clinical and genetic analysis of a case of Gitelman syndrome accompanied with Graves disease and adrenocortical adenoma: A case report

RATIONALE

Gitelman syndrome (GS), also known as familial hypokalemia and hypomagnesemia, is a rare autosomal recessive inherited disease caused by primary renal desalinization caused by impaired reabsorption of sodium and chloride ions in the distal renal tubules. We report a case of clinical and genetic characteristics of GS accompanied with Graves disease and adrenocorticotrophic hormone (ACTH)-independent adrenocortical adenoma.

PATIENT CONCERNS

The patient is a 45 year old female, was admitted to our hospital, due to a left adrenal gland occupying lesion as the chief complaint.

DIAGNOSIS

The patient was finally diagnosed as GS with Graves disease and adrenocortical adenoma.

INTERVENTIONS

Potassium magnesium aspartate (1788 mg/d, taken orally 3 times a day (supplement a few times a day, intake method, treatment duration). Contains 217.2 mg of potassium and 70.8 mg of magnesium, and potassium chloride (4.5 g/d, taken orally 3 times a day (supplement a few times a day, intake method, and treatment duration); Potassium 2356 mg), spironolactone (20 mg/d, taken orally once a day (supplement a few times a day, intake method, treatment duration). After 3 months of treatment, the patient's blood potassium fluctuated between 3.3-3.6 mmol/L, and blood magnesium fluctuated between 0.5-0.7 mmol/L, indicating a relief of fatigue symptoms.

OUTCOMES

On the day 6 of hospitalization, the symptoms of dizziness, limb fatigue, fatigue and pain were completely relieved on patient. In the follow-up of the following year, no recurrence of the condition was found.

LESSONS

The novel c.1444-10(IVS11)G > A variation may be a splicing mutation. The compound heterozygous mutations of the SLC12A3 gene may be the pathogenic cause of this GS pedigree.

From Fish Physiology to Human Disease: The Discovery of the NCC, NKCC2, and the Cation-Coupled Chloride Cotransporters

The renal Na-K-2Cl and Na-Cl cotransporters are the major salt reabsorption pathways in the thick ascending limb of Henle loop and the distal convoluted tubule, respectively. These transporters are the target of the loop and thiazide type diuretics extensively used in the world for the treatment of edematous states and arterial hypertension. The diuretics appeared in the market many years before the salt transport systems were discovered. The evolving of the knowledge and the cloning of the genes encoding the Na-K-2Cl and Na-Cl cotransporters were possible thanks to the study of marine species. This work presents the history of how we came to know the mechanisms for the loop and thiazide type diuretics actions, the use of marine species in the cloning process of these cotransporters and therefore in the whole solute carrier cotransproters 12 (SLC12) family of electroneutral cation chloride cotransporters, and the disease associated with each member of the family.

Gitelman syndrome combined with diabetes mellitus: A case report and literature review

RATIONALE

Gitelman syndrome (GS) is an uncommon autosomal recessive tubulopathy resulting from a functional deletion mutation in the SLC12A3 gene. Its onset is typically insidious and challenging to discern, and it is characterized by hypokalemia, metabolic alkalosis, and reduced urinary calcium excretion. There is limited literature on the diagnosis and management of GS in individuals with concomitant diabetes.

PATIENT CONCERNS

A 36-year-old male patient with a longstanding history of diabetes exhibited suboptimal glycemic control. Additionally, he presented with concurrent findings of hypokalemia, hypomagnesemia, hypocalciuria, and metabolic alkalosis.

DIAGNOSIS

Building upon the patient's clinical manifestations and extensive laboratory evaluations, we conducted thorough genetic testing, leading to the identification of a compound heterozygous mutation within the SLC12A3 gene. This definitive finding confirmed the diagnosis of GS.

INTERVENTIONS

We have formulated a detailed medication regimen for patients, encompassing personalized selection of hypoglycemic medications and targeted electrolyte supplementation.

OUTCOMES

Following 1 week of comprehensive therapeutic intervention, the patient's serum potassium level effectively normalized to 3.79 mmol/L, blood glucose parameters stabilized, and there was significant alleviation of clinical symptoms.

LESSONS

GS has a hidden onset and requires early diagnosis and intervention based on patient related symptoms and laboratory indicators in clinical practice, and personalized medication plans need to be provided according to the specific situation of the patient.

Long-Term Indomethacin Treatment in a Chinese Child with Gitelman Syndrome: Case Report and Literature Review on its Efficacy and Tolerance

BACKGROUND Gitelman syndrome (GS) is a rare inherited autosomal recessive salt-losing renal tubulopathy. Early-onset GS is difficult to differentiate from Bartter syndrome (BS). It has been reported in some cases that cyclooxygenase (COX) inhibitors, which pharmacologically reduce prostaglandin E2(PGE2) synthesis, are helpful for GS patients, especially in children, but the long-term therapeutic effect has not yet been revealed. CASE REPORT A 4-year-old boy was first brought to our hospital for the chief concern of short stature and growth retardation. Biochemical tests demonstrated severe hypokalemia, hyponatremia, and hypochloremic metabolic alkalosis. The patient's serum magnesium was normal. He was diagnosed with BS and treated with potassium supplementation and indomethacin and achieved stable serum potassium levels and slow catch-up growth. At 11.8 years of age, the patient showed hypomagnesemia and a genetic test confirmed that he had GS with compound heterozygous mutations in the SLC12A3 gene. At the age of 14.8 years, when indomethacin had been taken for nearly 10 years, the boy reported having chronic stomachache, while his renal function remained normal. After proton pump inhibitor and acid inhibitor therapy, the patient's symptoms were ameliorated, and he continued to take a low dose of indomethacin (37.5 mg/d divided tid) with good tolerance. CONCLUSIONS Early-onset GS in childhood can be initially misdiagnosed as BS, and gene detection can confirm the final diagnosis. COX inhibitors, such as indomethacin, might be tolerated by pediatric patients, and long-term therapy can improve the hypokalemia and growth retardation without significant adverse effects.

Electrolyte Disorders in Mitochondrial Cytopathies: A Systematic Review

SIGNIFICANCE STATEMENT

Several recent studies identified mitochondrial mutations in patients with Gitelman or Fanconi syndrome. Mitochondrial cytopathies are generally not considered in the diagnostic workup of patients with electrolyte disorders. In this systematic review, we investigated the presence of electrolyte disorders in patients with mitochondrial cytopathies to determine the relevance of mitochondrial mutation screening in this population. Our analysis demonstrates that electrolyte disorders are commonly reported in mitochondrial cytopathies, often as presenting symptoms. Consequently, more clinical attention should be raised for mitochondrial disease as cause for disturbances in electrolyte homeostasis. Further prospective cohort studies are required to determine the exact prevalence of electrolyte disorders in mitochondrial cytopathies.

BACKGROUND

Electrolyte reabsorption in the kidney has a high energy demand. Proximal and distal tubular epithelial cells have a high mitochondrial density for energy release. Recently, electrolyte disorders have been reported as the primary presentation of some mitochondrial cytopathies. However, the prevalence and the pathophysiology of electrolyte disturbances in mitochondrial disease are unknown. Therefore, we systematically investigated electrolyte disorders in patients with mitochondrial cytopathies.

METHODS

We searched PubMed, Embase, and Google Scholar for articles on genetically confirmed mitochondrial disease in patients for whom at least one electrolyte is reported. Patients with a known second genetic anomaly were excluded. We evaluated 214 case series and reports (362 patients) as well as nine observational studies. Joanna Briggs Institute criteria were used to evaluate the quality of included studies.

RESULTS

Of 362 reported patients, 289 had an electrolyte disorder, with it being the presenting or main symptom in 38 patients. The average number of different electrolyte abnormalities per patient ranged from 2.4 to 1.0, depending on genotype. Patients with mitochondrial DNA structural variants seemed most affected. Reported pathophysiologic mechanisms included renal tubulopathies and hormonal, gastrointestinal, and iatrogenic causes.

CONCLUSIONS

Mitochondrial diseases should be considered in the evaluation of unexplained electrolyte disorders. Furthermore, clinicians should be aware of electrolyte abnormalities in patients with mitochondrial disease.

Gitelman Syndrome and Hypertension: A Case Report

In a patient with persistent hypokalemia, it is important to consider Gitelman syndrome, a rare, salt-wasting tubulopathy inherited in an autosomal recessive pattern. Gitelman syndrome leads to electrolyte abnormalities like hypokalemia, hypomagnesemia, and metabolic alkalosis. Typical clinical features include muscle cramps, fatigue, polydipsia, and salt cravings. Our case involves a female patient in her early 40s who visited the endocrinology clinic with symptoms of polyuria, constipation, muscle weakness, and fatigue. Electrolyte abnormalities included hypokalemia, hypomagnesemia, hypochloremia, and hyperreninemia. Initial tests, such as renal function tests, renal ultrasound, and CT scan, yielded normal results. Differential diagnosis of Gitelman syndrome and Bartter syndrome was considered due to the mutual electrolyte abnormalities of hypokalemia and metabolic alkalosis. Bartter syndrome was ruled out in our patient due to the presence of hypomagnesemia, which indicates a different defective receptor. Ultimately, genetic testing would be necessary to confirm the diagnosis of Gitelman syndrome considering the characteristic electrolyte disturbances and classic clinical presentation of fatigue, weakness, and salt craving.

Novel heterozygous mutations of SLC12A3 gene in a Chinese pedigree with Gitelman syndrome: A care-compliant case report

RATIONALE

The diagnosis of Gentleman syndrome (GS) is usually delayed because the clinical symptoms are easily mistaken.

PATIENT CONCERNS

A 19-year-old male patient was referred to endocrinology due to intermittent twitch of extremities for approximately 7 years.

DIAGNOSES

The diagnosis of GS was made based on the laboratory and gene detection results. We identified 2 new variants in the SLC12A3 gene [c.857 A > C (exon7) and c.2089_2095del (exon17)] in his Asian family.

INTERVENTIONS

The patient received the treatment of potassium chloride sustained release tablets, potassium magnesium aspartate and spironolactone. After given potassium supplement through enema, his serum potassium level was corrected to normal.

OUTCOMES

The electrolyte imbalance including hypokalemia and hypomagnesemia were improved with a remission of the clinical manifestations. But the patient's condition still could not remain stable for his irregular oral potassium supplementation during the follow-up of nearly 3 months.

LESSONS

Our finding broadens the variant spectrum of SLC12A3 and contributes to a more quickly genetic counseling. As a result, when a patient presents with persistent, unspecified, and inadequately treated hypokalemia, tests for GS should indeed be considered. For suspected cases of GS, genetic testing should always be considered in the diagnosis.

Gitelman Syndrome Manifesting With Acute Hypokalemic Paralysis: A Case Report

Gitelman syndrome (GS) is a rare renal tubulopathy, classically characterized by renal salt wasting and metabolic alkalosis. It is usually an incidental diagnosis, being asymptomatic or with mild symptoms. GS manifesting with acute flaccid paralysis is extremely uncommon. We report a case of GS that mimicked Guillain-Barré syndrome (GBS), manifesting with acute hypokalemic paralysis. A middle-aged male with no known comorbidities presented to our center with paresthesias of all four limbs for one month and progressive, asymmetric limb weakness over the past eight days. Neurological examination revealed hypotonia, global areflexia, and power ranging from 3/5 to 4/5 in all four limbs, leading to our initial clinical diagnosis of GBS. Our patient's laboratory panel revealed hypokalemia, hypomagnesemia, metabolic alkalosis, and hypocalcemia, characteristic of GS. Additionally, he had significantly elevated creatine phosphokinase, suggestive of rhabdomyolysis. Further urine studies revealed renal potassium wasting, confirming the diagnosis of GS. Whole exome genome sequencing for common causative genes and workup for autoimmune disease were both negative. With gradual electrolyte correction, the patient rapidly improved symptomatically. Our case highlights an uncommon initial presentation of GS and emphasizes the need for more literature on its manifestations from the Indian subcontinent.

Heart's Dangerous Symphony: Torsade De Pointes Unleashed by Gitelman Syndrome-Induced Hypomagnesemia

Gitelman syndrome (GS) is a rare autosomal recessive salt-losing renal tubular disorder associated with a mutation of SLC12A3 or CLCNKB genes which encodes the thiazide-sensitive sodium-chloride co-transporter (NCCT) in the distal renal tubule. It is inherited as an autosomal recessive disorder. Hypokalemia, metabolic alkalosis, hypomagnesemia, hypocalciuria, and renin-angiotensin-aldosterone system (RAAS) activation are characteristics of GS. GS is often misdiagnosed or underdiagnosed owing to its low incidence and lack of awareness. Its prevalence is estimated to be around 1-10 per 40,000 people. We report a case of cardiac arrest secondary to torsade de pointes (TdP) because of GS-induced hypomagnesemia. Our case highlights the importance of clinicians being aware of the potential electrolyte abnormalities and complications associated with GS, as it can lead to catastrophic consequences if not identified and corrected earlier.

Thiazides Attenuate Insulin Secretion Through Inhibition of Mitochondrial Carbonic Anhydrase 5b in β -Islet Cells in Mice

SIGNIFICANCE STATEMENT

Thiazide diuretics (thiazides) are among the most widely prescribed drugs worldwide, but their use is associated with glucose intolerance and new-onset diabetes mellitus. The molecular mechanisms remain elusive. Our study reveals that thiazides attenuate insulin secretion through inhibition of the mitochondrial carbonic anhydrase isoform 5b (CA5b) in pancreatic β cells. We furthermore discovered that pancreatic β cells express only one functional carbonic anhydrase isoform, CA5b, which is critical in replenishing oxaloacetate in the mitochondrial tricarboxylic acid (TCA) cycle (anaplerosis). These findings explain the mechanism for thiazide-induced glucose intolerance and reveal a fundamental role of CA5b in TCA cycle anaplerosis and insulin secretion in β cells.

BACKGROUND

Thiazide diuretics are associated with glucose intolerance and new-onset diabetes mellitus. Previous studies demonstrated that thiazides attenuate insulin secretion, but the molecular mechanisms remain elusive. We hypothesized that thiazides attenuate insulin secretion via one of the known molecular thiazide targets in β cells.

METHODS

We performed static insulin secretion experiments with islets of wild-type, Sodium/chloride co-transporter (NCC) (SLC12A3), and sodium-driven chloride/bicarbonate exchanger (NDCBE) (SLC4A8) knock-out (KO) mice and with murine Min6 cells with individual knockdown of carbonic anhydrase (CA) isoforms to identify the molecular target of thiazides in β cells. CA isoform 5b (CA5b) KO mice were then used to assess the role of the putative thiazide target CA5b in β -cell function and in mediating thiazide sensitivity in vitro and in vivo .

RESULTS

Thiazides inhibited glucose- and sulfonylurea-stimulated insulin secretion in islets and Min6 cells at pharmacologically relevant concentrations. Inhibition of insulin secretion by thiazides was CO 2 /HCO 3- -dependent, not additive to unselective CA inhibition with acetazolamide, and independent of extracellular potassium. By contrast, insulin secretion was unaltered in islets of mice lacking the known molecular thiazide targets NCC or NDCBE. CA expression profiling with subsequent knockdown of individual CA isoforms suggested mitochondrial CA5b as a molecular target. In support of these findings, thiazides significantly attenuated Krebs cycle anaplerosis through reduction of mitochondrial oxaloacetate synthesis. CA5b KO mice were resistant to thiazide-induced glucose intolerance, and thiazides did not alter insulin secretion in CA5b KO islets.

CONCLUSIONS

Thiazides attenuate insulin secretion via inhibition of the mitochondrial CA5b isoform in β cells of mice.

Case report: Gitelman syndrome with diabetes: Confirmed by both hydrochlorothiazide test and genetic testing

RATIONALE

Gitelman syndrome (GS) is an autosomal recessive tubulopathy caused by mutations of the SLC12A3 gene. It is characterized by hypokalemic metabolic alkalosis, hypomagnesemia and hypocalciuria. Hypokalemia, hypomagnesemia, and increased renin-angiotensin-aldosterone system (RAAS) activity can cause glucose metabolism dysfunction. The diagnosis of GS includes clinical diagnosis, genetic diagnosis and functional diagnosis. The gene diagnosis is the golden criterion while as functional diagnosis is of great value in differential diagnosis. The hydrochlorothiazide (HCT) test is helpful to distinguish GS from batter syndrome, but few cases have been reported to have HCT testing.

PATIENT CONCERNS

A 51-year-old Chinese woman presented to emergency department because of intermittent fatigue for more than 10 years.

DIAGNOSES

Laboratory test results showed hypokalemia, hypomagnesemia, hypocalciuria and metabolic alkalosis. The HCT test showed no response. Using next-generation and Sanger sequencing, we identified 2 heterozygous missense variants (c.533C > T:p.S178L and c.2582G > A:p.R861H) in the SLC12A3 gene. In addition, the patient was diagnosed with type 2 diabetes mellitus 7 years ago. Based on these findings, the patient was diagnosed with GS with type 2 diabetic mellitus (T2DM).

INTERVENTIONS

She was given potassium and magnesium supplements, and dapagliflozin was used to control her blood glucose.

OUTCOMES

After treatments, her fatigue symptoms were reduced, blood potassium and magnesium levels were increased, and blood glucose levels were well controlled.

LESSONS

When GS is considered in patients with unexplained hypokalemia, the HCT test can be used for differential diagnosis, and genetic testing can be continued to confirm the diagnosis when conditions are available. GS patients often have abnormal glucose metabolism, which is mainly caused by hypokalemia, hypomagnesemia, and secondary activation of RAAS. When a patient is diagnosed with GS and type 2 diabetes, sodium-glucose cotransporter 2 inhibitors (SGLT2i) can be used to control the blood glucose level and assist in raising blood magnesium.

Gitelman Syndrome: A Case Report

Gitelman syndrome is a rare hereditary tubulopathy characterized by hypokalemic metabolic alkalosis, hypomagnesemia, and hypocalciuria. In this case report, we describe a 21-year-old male who presented with myalgias, asthenia, general muscle weakness, and hypokalemia after receiving oral potassium supplementation for six months. Additional biochemical studies showed hypomagnesemia, metabolic alkalosis, and increased urinary potassium and magnesium excretion. Calcium urinary excretion was within the normal range, but 25-hydroxycholecalciferol levels were low. Systolic arterial hypertension was found, probably reflecting chronic hyperreninemic hyperaldosteronism. Genetic testing for SCL12A3 mutations identified a pathogenic variant in homozygosity, which confirmed the Gitelman syndrome diagnosis. Treatment with chronic potassium and magnesium oral supplementation was started, as well as eplerenone and amiloride, with sustained correction of hypokalemia and hypomagnesemia.

Long-Read Sequencing Identifies Novel Pathogenic Intronic Variants in Gitelman Syndrome

BACKGROUND

Gitelman syndrome is a salt-losing tubulopathy characterized by hypokalemic alkalosis and hypomagnesemia. It is caused by homozygous recessive or compound heterozygous pathogenic variants in SLC12A3 , which encodes the Na + -Cl - cotransporter (NCC). In up to 10% of patients with Gitelman syndrome, current genetic techniques detect only one specific pathogenic variant. This study aimed to identify a second pathogenic variant in introns, splice sites, or promoters to increase the diagnostic yield.

METHODS

Long-read sequencing of SLC12A3 was performed in 67 DNA samples from individuals with suspected Gitelman syndrome in whom a single likely pathogenic or pathogenic variant was previously detected. In addition, we sequenced DNA samples from 28 individuals with one variant of uncertain significance or no candidate variant. Midigene splice assays assessed the pathogenicity of novel intronic variants.

RESULTS

A second likely pathogenic/pathogenic variant was identified in 45 (67%) patients. Those with two likely pathogenic/pathogenic variants had a more severe electrolyte phenotype than other patients. Of the 45 patients, 16 had intronic variants outside of canonic splice sites (nine variants, mostly deep intronic, six novel), whereas 29 patients had an exonic variant or canonic splice site variant. Midigene splice assays of the previously known c.1670-191C>T variant and intronic candidate variants demonstrated aberrant splicing patterns.

CONCLUSION

Intronic pathogenic variants explain an important part of the missing heritability in Gitelman syndrome. Long-read sequencing should be considered in diagnostic workflows for Gitelman syndrome.

Cardiac Arrest as the First Presentation of Gitelman Syndrome

Gitelman syndrome is a salt-wasting tubulopathy characterized by profound hypokalemia, hypomagnesemia, metabolic alkalosis, and hypocalciuria. Cardiac arrest is a relatively rare manifestation of Gitelman syndrome. Here we present a case of Gitelman syndrome in a patient with recurrent cardiac arrest. A 43-year-old female was admitted for out-of-hospital cardiac arrest secondary to ventricular fibrillation. Initial workup revealed severe hypokalemia, hypomagnesemia, metabolic alkalosis, and prolonged QTc. The workup revealed a picture of salt-wasting tubulopathy with hypokalemia, hypomagnesemia, and hypocalciuria. Potassium was repleted aggressively, and the patient received potassium-sparing agents resulting in the stabilization of potassium levels. Before discharge, an implantable cardioverter defibrillator (ICD) was placed for secondary prevention of cardiac arrest. The patient remained symptom-free, and electrolytes remained stable. This case highlights the diagnostic challenges of Gitelman syndrome and the importance of accurate diagnosis in improving patient outcomes.

The genetic spectrum of Gitelman(-like) syndromes

PURPOSE OF REVIEW

Gitelman syndrome is a recessive salt-wasting disorder characterized by hypomagnesemia, hypokalemia, metabolic alkalosis and hypocalciuria. The majority of patients are explained by mutations and deletions in the SLC12A3 gene, encoding the Na+-Cl--co-transporter (NCC). Recently, additional genetic causes of Gitelman-like syndromes have been identified that should be considered in genetic screening. This review aims to provide a comprehensive overview of the clinical, genetic and mechanistic aspects of Gitelman(-like) syndromes.

RECENT FINDINGS

Disturbed Na+ reabsorption in the distal convoluted tubule (DCT) is associated with hypomagnesemia and hypokalemic alkalosis. In Gitelman syndrome, loss-of-function mutations in SLC12A3 cause impaired NCC-mediated Na+ reabsorption. In addition, patients with mutations in CLCKNB, KCNJ10, FXYD2 or HNF1B may present with a similar phenotype, as these mutations indirectly reduce NCC activity. Furthermore, genetic investigations of patients with Na+-wasting tubulopathy have resulted in the identification of pathogenic variants in MT-TI, MT-TF, KCNJ16 and ATP1A1. These novel findings highlight the importance of cell metabolism and basolateral membrane potential for Na+ reabsorption in the DCT.

SUMMARY

Altogether, these findings extend the genetic spectrum of Gitelman-like electrolyte alterations. Genetic testing of patients with hypomagnesemia and hypokalemia should cover a panel of genes involved in Gitelman-like syndromes, including the mitochondrial genome.

Pseudo-pheochromocytoma due to obstructive sleep apnea: a case report

SUMMARY

Obstructive sleep apnea (OSA) is a condition of intermittent nocturnal upper airway obstruction. OSA increases sympathetic drive which may result in clinical and biochemical features suggestive of pheochromocytoma. We present the case of a 65-year-old male with a 2.9-cm left adrenal incidentaloma on CT, hypertension, symptoms of headache, anxiety and diaphoresis, and persistently elevated 24-h urine norepinephrine (initially 818 nmol/day (89-470)) and normetanephrine (initially 11.2 µmol/day (0.6-2.7)). He was started on prazosin and underwent left adrenalectomy. Pathology revealed an adrenal corticoadenoma with no evidence of pheochromocytoma. Over the next 2 years, urine norepinephrine and normetanephrine remained significantly elevated with no MIBG avid disease. Years later, he was diagnosed with severe OSA and treated with continuous positive airway pressure. Urine testing done once OSA was well controlled revealed complete normalization of urine norepinephrine and normetanephrine with substantial symptom improvement. It was concluded that the patient never had a pheochromocytoma but rather an adrenal adenoma with biochemistry and symptoms suggestive of pheochromocytoma due to untreated severe OSA. Pseudo-pheochromocytoma is a rare presentation of OSA and should be considered on the differential of elevated urine catecholamines and metanephrines in the right clinical setting.

LEARNING POINTS

Obstructive sleep apnea (OSA) is a common condition among adults. OSA may rarely present as pseudo-pheochromocytoma with symptoms of pallor, palpitations, perspiration, headache, or anxiety. OSA should be considered on the differential of elevated urine catecholamines and metanephrines, especially in patients with negative metaiodobenzylguanidine (MIBG) scan results.

Molecular mechanisms for the modulation of blood pressure and potassium homeostasis by the distal convoluted tubule

Epidemiological and clinical observations have shown that potassium ingestion is inversely correlated with arterial hypertension prevalence and cardiovascular mortality. The higher the dietary potassium, the lower the blood pressure and mortality. This phenomenon is explained, at least in part, by the interaction between salt reabsorption in the distal convoluted tubule (DCT) and potassium secretion in the connecting tubule/collecting duct of the mammalian nephron: In order to achieve adequate K⁺ secretion levels under certain conditions, salt reabsorption in the DCT must be reduced. Because salt handling by the kidney constitutes the basis for the long‐term regulation of blood pressure, losing salt prevents hypertension. Here, we discuss how the study of inherited diseases in which salt reabsorption in the DCT is affected has revealed the molecular players, including membrane transporters and channels, kinases, and ubiquitin ligases that form the potassium sensing mechanism of the DCT and the processes through which the consequent adjustments in salt reabsorption are achieved.

Euglycemic Diabetic Ketoacidosis Due to SGLT2 Inhibitor in a Patient With Gitelman Syndrome: A Therapeutic Dilemma

Euglycemic diabetic ketoacidosis (DKA) is a rarely reported side effect of sodium-glucose cotransporter-2 inhibitor (SGLT2i) empagliflozin. A 51-year-old female with Gitelman syndrome and type 2 diabetes mellitus (DM) presented with abdominal pain after a recent hospitalization for acute pancreatitis. Her diabetes medications included metformin, pioglitazone, and empagliflozin. Diabetic ketoacidosis was suspected; however, glucose levels were below the cutoff for DKA; therefore, she was diagnosed with euglycemic DKA. Her pancreatitis workup was insignificant. Severe symptomatic hypokalemia despite aggressive repletion limited the management of DKA with insulin infusion therapy. As her ketonemia resolved, she was initiated on subcutaneous insulin with a small but acceptable decrease in potassium. The therapeutic dilemma of managing euglycemic DKA due to SGLT2i in a patient with Gitelman syndrome has not been previously described.

A Challenging Case of Persisting Hypokalemia Secondary to Gitelman Syndrome

There are several causes of hypokalemia, including transcellular shift, renal loss, gastrointestinal loss, and decreased oral intake. Sometimes it is challenging to know the source of the problem; however, with detailed history, physical examination, and appropriate laboratory investigations, the physician should be able to narrow down the differentials diagnosis to reach the right one. One of the rare causes of hypokalemia is Gitelman syndrome, which is a salt-losing tubulopathy that manifests as renal potassium wasting, metabolic alkalosis, hypokalemia, hypomagnesemia, hypocalciuria, and hyperreninemic hyperaldosteronism. This disorder is inherited in an autosomal recessive pattern with an incidence of 25 instances per million population. We report a challenging case of persistent hypokalemia in a 30-year-old woman who presented with a history of palpitation, bilateral upper and lower limbs numbness, nausea, diarrhea, and generalized fatigue for three days. After history and physical examination, the patient was diagnosed with an episode of enteritis, and laboratory workups revealed low potassium and magnesium levels, and it was thought that these electrolyte abnormalities were secondary to gastrointestinal loss. Therefore, the patient was mainly treated supportively along with potassium and magnesium replacement. However, after one week of replacement, the patient still had low potassium and magnesium levels in spite of being diarrhea-free, so renal loss was suspected. Urine electrolytes revealed high renal potassium loss with low-normal blood pressure, arterial blood gases revealed metabolic alkalosis with a pH of 7.49 and bicarbonate level of 29 mEq/L. Repeated urine chemistry was done to check for chloride level and turned out to be high, and 24-hour urinary excretion of calcium was very low. Therefore, the patient was diagnosed with Gitelman syndrome and was managed with potassium and magnesium replacements intravenously, and was encouraged to consume a diet rich in these electrolytes. After complete resolutions of the symptoms and correction of potassium and magnesium levels, the patient was discharged home in stable condition.

Gitelman Syndrome Provisionally Diagnosed During the First Presentation of Diabetic Ketoacidosis

Gitelman syndrome (GS) is an autosomal recessive disease characterized by hypokalemia, hypomagnesemia, metabolic alkalosis, and hypocalciuria. It is caused by mutations in gene SLC12A3 (located in chromosome 16q) encoding NaCl cotransporter. GS is usually asymptomatic for several years and is diagnosed in late childhood or adulthood. The association between GS and diabetic ketoacidosis (DKA) is rare. We present a case of a 25-year-old man with newly diagnosed diabetes mellitus and DKA with profound hypokalemia and hypomagnesemia who was provisionally found to have GS.

Type 2 diabetes mellitus caused by Gitelman syndrome-related hypokalemia: A case report

INTRODUCTION

Gitelman syndrome (GS) is an autosomal-recessive disease caused by SLC12A3 gene mutations. It is characterized by hypokalemic metabolic alkalosis in combination with hypomagnesemia and hypocalciuria. Recently, patients with GS are found at an increased risk for developing type 2 diabetes mellitus (T2DM). However, diagnosis of hyperglycemia in GS patients has not been thoroughly investigated, and family studies on SLC12A3 mutations and glucose metabolism are rare. Whether treatment including potassium and magnesium supplements, and spironolactone can ameliorate impaired glucose tolerance in GS patients, also needs to be investigated.

PATIENT CONCERNS

We examined a 55-year-old Chinese male with intermittent fatigue and persistent hypokalemia for 17 years.

DIAGNOSES

Based on the results of the clinical data, including electrolytes, oral glucose tolerance test (OGTT), and genetic analysis of the SLC12A3 gene, GS and T2DM were newly diagnosed in the patient. Two mutations of the SLC12A3 gene were found in the patient, one was a missense mutation p.N359K in exon 8, and the other was a novel insert mutation p.I262delinsIIGVVSV in exon 6. SLC12A3 genetic analysis and OGTT of 9 other family members within 3 generations were also performed. Older brother, youngest sister, and son of the patient carried the p.N359K mutation in exon 8. The older brother and the youngest sister were diagnosed with T2DM and impaired glucose tolerance by OGTT, respectively.

INTERVENTIONS

The patient was prescribed potassium and magnesium (potassium magnesium aspartate, potassium chloride) oral supplements and spironolactone. The patient was also suggested to maintain a high potassium diet. Acarbose was used to maintain the blood glucose levels.

OUTCOMES

The electrolyte imbalance including hypokalemia and hypomagnesemia, and hyperglycemia were improved with a remission of the clinical manifestations.

CONCLUSION

GS is one of the causes for manifestation of hypokalemia. SLC12A3 genetic analysis plays an important role in diagnosis of GS. Chinese male GS patients characterized with heterozygous SLC12A3 mutation should be careful toward occurrence of T2DM. Moreover, the patients with only 1 SLC12A3 mutant allele should pay regular attention to blood potassium and glucose levels. GS treatment with potassium and magnesium supplements, and spironolactone can improve impaired glucose metabolism.

Gitelman syndrome combined with growth hormone deficiency: Three cases report

RATIONALE

Gitelman syndrome (GS) is a rare autosomal recessive hereditary salt-losing tubulopathy caused by loss-of-function mutations in the SLC12A3 gene. It is usually characterized by hypokalemia, metabolic alkalosis, hypomagnesemia, and hypocalciuria. There are only a few reports on GS combined with growth hormone deficiency (GHD).

PATIENT CONCERNS

Three patients presented with weakness, spasm, and growth retardation, respectively.

DIAGNOSES

GS was diagnosed based on the clinical symptoms, laboratory test results, and genetic analysis. GH stimulation tests were performed when the magnesium level returned to normal under magnesium oxide (MgO) therapy.

INTERVENTIONS

Initially, all patients received oral replacement of MgO and potassium chloride, and 2 of them received simultaneous spironolactone therapy. Recombinant human growth hormone (rhGH) therapy was initiated after they were diagnosed with GHD.

OUTCOMES

All 3 patients exhibited satisfactory growth velocity and normal serum magnesium level, although the potassium level was still slightly lower than normal.

LESSONS

We suggest that all GS patients should undergo genetic evaluation, especially regarding SLC12A3 gene mutation. GHD should be considered if these patients have short stature. rhGH therapy is useful for stimulating the patients' growth, and it may increase the serum magnesium level.

Acquired Gitelman Syndrome in an Anti-SSA Antibody-positive Patient with a SLC12A3 Heterozygous Mutation

A 36-year-old woman developed hypokalemic metabolic alkalosis after anti SS-A antibody was found to be positive. Diuretic loading test results were compatible with Gitelman syndrome (GS). The patient had a heterozygous mutation in SLC12A3, which encodes for thiazide-sensitive NaCl cotransporter (NCCT). While the mutation may be responsible for a latent hypofunction of NCCTs, the underlying anti-SSA antibody-associated autoimmunity induced the manifestation of its hypofunction. To the best of our knowledge, this is the first report to demonstrate that anti SS-A antibody-associated autoimmunity may induce GS in a patient with a SLC12A3 heterozygous mutation.

Bartter- and Gitelman-like syndromes: salt-losing tubulopathies with loop or DCT defects

Salt-losing tubulopathies with secondary hyperaldosteronism (SLT) comprise a set of well-defined inherited tubular disorders. Two segments along the distal nephron are primarily involved in the pathogenesis of SLTs: the thick ascending limb of Henle's loop, and the distal convoluted tubule (DCT). The functions of these pre- and postmacula densa segments are quite distinct, and this has a major impact on the clinical presentation of loop and DCT disorders - the Bartter- and Gitelman-like syndromes. Defects in the water-impermeable thick ascending limb, with its greater salt reabsorption capacity, lead to major salt and water losses similar to the effect of loop diuretics. In contrast, defects in the DCT, with its minor capacity of salt reabsorption and its crucial role in fine-tuning of urinary calcium and magnesium excretion, provoke more chronic solute imbalances similar to the effects of chronic treatment with thiazides. The most severe disorder is a combination of a loop and DCT disorder similar to the enhanced diuretic effect of a co-medication of loop diuretics with thiazides. Besides salt and water supplementation, prostaglandin E2-synthase inhibition is the most effective therapeutic option in polyuric loop disorders (e.g., pure furosemide and mixed furosemide-amiloride type), especially in preterm infants with severe volume depletion. In DCT disorders (e.g., pure thiazide and mixed thiazide-furosemide type), renin-angiotensin-aldosterone system (RAAS) blockers might be indicated after salt, potassium, and magnesium supplementation are deemed insufficient. It appears that in most patients with SLT, a combination of solute supplementation with some drug treatment (e.g., indomethacin) is needed for a lifetime.

Inherited forms of renal hypomagnesemia: an update

The kidney plays an important role in ion homeostasis in the human body. Several hereditary disorders characterized by perturbations in renal magnesium reabsorption leading to hypomagnesemia have been described over the past 50 years, with the most important of these being Gitelman syndrome, familial hypomagnesemia with hypercalciuria and nephrocalcinosis, familial hypomagnesemia with secondary hypocalcemia, autosomal dominant hypomagnesemia with hypocalciuria, and autosomal recessive hypomagnesemia. Only recently, following positional cloning strategies in affected families, have mutations in renal ion channels and transporters been identified in these diseases. In this short review, I give an update on these hypomagnesemic disorders. Elucidation of the genetic etiology and, for most of these disorders, also the underlying pathophysiology of the disease, has greatly increased our understanding of the normal physiology of renal magnesium handling. This is yet another example of the importance of studying rare disorders in order to unravel physiological and pathophysiological processes in the human body.