Clinicopathological Features of Gitelman Syndrome with Proteinuria and Renal Dysfunction

INTRODUCTION

Gitelman syndrome (GS) is a rare renal tubular salt-wasting disorder. Besides kidney electrolyte loss, proteinuria and renal dysfunction were also observed. However, their incidence, risk factors, pathological features, and prognosis were unclear.

METHODS

We retrospectively reviewed 116 GS patients and analyzed their clinical, genetic, and pathological characteristics. We also systematically reviewed articles on GS with proteinuria and renal dysfunction.

RESULTS

Twenty-three GS patients had proteinuria (69.6%) and renal dysfunction (43.5%) with a mean age of 35.3 ± 13.2 years, and 65.2% were male. Compared to patients without proteinuria or renal dysfunction, these patients had elevated plasma angiotensin II level (440.2 ± 351.7 vs. 253.2 ± 187.4 pg/mL, p = 0.031) and three times higher incidence of diabetes. The renal pathology of nine biopsied patients indicated hypertrophy of the juxtaglomerular apparatus (100%), chronic tubulointerstitial changes (66.7%), intrarenal vascular changes (66.7%), and glomerulopathy (55.6%). More extensive renin staining was observed in patients with GS than in the control group with glomerular minor lesion (p < 0.001). During a median of 85 months (range, 11-205 months) of follow-up for 19 out of the 23 GS-renal patients, the renal function was generally stable, except one died of cancer and one developed end-stage renal disease because of concomitant membranous nephropathy and IgA nephropathy.

CONCLUSION

Proteinuria and renal dysfunction were more common than expected and might indicate glomerulopathy and vascular lesions besides a tubulointerstitial injury in GS. Renal function may maintain stable with effective therapy in most cases.

A case of Gitelman syndrome with membranous nephropathy

Background

Gitelman syndrome (GS) is a rare autosomal recessive inherited salt-losing tubulopathy (SLT). Here, we report, for the first time, a case of GS overlapping nephrotic syndrome (NS) related to PLA2R-associated membranous nephropathy (MN).

Case presentation

We described a male patient had a 4-year history of recurrent fatigue. Serum biochemistry revealed hypokalemia with renal potassium wasting, hypomagnesemia, metabolic alkalosis, hyperreninemia, hypocalciuria, as well as nephrotic-range proteinuria, hypoalbuminemia, and elevated serum anti-phospholipase A2 receptor (PLA2R) antibody. Gene sequencing identified compound heterozygous mutations in SLC12A3 [c.536T > A(p.V179D) and c.1456G > A(p.D486N)]. The unusual association of SLTs and nephrotic-range glomerular proteinuria prompted us to perform a renal biopsy. Renal biopsy showed idiopathic MN. Due to the potential to activate the sodium-chloride co-transporter (NCC) and cause hyperkalemia, tacrolimus was selected to treat NS. Following treatment with potassium chloride, magnesium oxide, low-dose glucocorticoid combined with tacrolimus, the fatigue significantly improved, and concurrently hypokalemia, hypomagnesemia were corrected and NS was remitted.

Conclusions

Renal biopsy should be warranted for GS patients with moderate to nephrotic-range proteinuria. Tacrolimus was preferred to the management of GS patients with NS.

Potassium and the kidney: a reciprocal relationship with clinical relevance

By controlling urinary potassium excretion, the kidneys play a key role in maintaining whole-body potassium homeostasis. Conversely, low urinary potassium excretion (as a proxy for insufficient dietary intake) is increasingly recognized as a risk factor for the progression of kidney disease. Thus, there is a reciprocal relationship between potassium and the kidney: the kidney regulates potassium balance but potassium also affects kidney function. This review explores this relationship by discussing new insights into kidney potassium handling derived from recently characterized tubulopathies and studies on sexual dimorphism. These insights reveal a central but non-exclusive role for the distal convoluted tubule in sensing potassium and subsequently modifying the activity of the sodium-chloride cotransporter. This is another example of reciprocity: activation of the sodium-chloride cotransporter not only reduces distal sodium delivery and therefore potassium secretion but also increases salt sensitivity. This mechanism helps explain the well-known relationship between dietary potassium and blood pressure. Remarkably, in children, blood pressure is related to dietary potassium but not sodium intake. To explore how potassium deficiency can cause kidney injury, we review the mechanisms of hypokalemic nephropathy and discuss if these mechanisms may explain the association between low dietary potassium intake and adverse kidney outcomes. We discuss if potassium should be repleted in patients with kidney disease and what role dietary potassium plays in the risk of hyperkalemia. Supported by data and physiology, we reach the conclusion that we should view potassium not only as a potentially dangerous cation but also as a companion in the battle against kidney disease.

Molecular Basis, Diagnostic Challenges and Therapeutic Approaches of Bartter and Gitelman Syndromes: A Primer for Clinicians

Gitelman and Bartter syndromes are rare inherited diseases that belong to the category of renal tubulopathies. The genes associated with these pathologies encode electrolyte transport proteins located in the nephron, particularly in the Distal Convoluted Tubule and Ascending Loop of Henle. Therefore, both syndromes are characterized by alterations in the secretion and reabsorption processes that occur in these regions. Patients suffer from deficiencies in the concentration of electrolytes in the blood and urine, which leads to different systemic consequences related to these salt-wasting processes. The main clinical features of both syndromes are hypokalemia, hypochloremia, metabolic alkalosis, hyperreninemia and hyperaldosteronism. Despite having a different molecular etiology, Gitelman and Bartter syndromes share a relevant number of clinical symptoms, and they have similar therapeutic approaches. The main basis of their treatment consists of electrolytes supplements accompanied by dietary changes. Specifically for Bartter syndrome, the use of non-steroidal anti-inflammatory drugs is also strongly supported. This review aims to address the latest diagnostic challenges and therapeutic approaches, as well as relevant recent research on the biology of the proteins involved in disease. Finally, we highlight several objectives to continue advancing in the characterization of both etiologies.

Gitelman syndrome with a novel frameshift variant in SLC12A3 gene accompanied by chronic kidney disease and type 2 diabetes mellitus

Gitelman syndrome is an autosomal recessive genetic disease caused by pathogenic variants in SLC12A3 resulting in the loss of function of the Na-Cl co-transporter (NCC) in the distal tubules. Hypokalemia and diuretic effects can cause secondary type 2 diabetes and renal function decline. Here, we present the case of a 49-year-old male patient with chronic persistent treatment-resistant hypokalemia for the past 13 years who had been receiving treatment for type 2 diabetes mellitus for 6 years. He was referred to our department due to the presence of urinary protein, impaired renal function, high renin activity, and hyperaldosteronism. Laboratory test results showed hypokalemia, hypomagnesemia, hypocalciuria, and metabolic alkalosis. Using next-generation and Sanger sequencing, we identified a novel stop-gain variant (NM_000339.3:c.137del [p.His47fs]) and a missense variant (NM_000339.3:c.2927C > T [p.Ser976Phe]) in the SLC12A3 gene. This novel pathogenic variant was located at the intracellular N-terminus of the NCC. Based on these findings, the patient was diagnosed with Gitelman syndrome. The use of next-generation sequencing facilitated the exclusion of diseases with similar clinical symptoms.

Kidney stones and moderate proteinuria as the rare manifestations of Gitelman syndrome

Background

Gitelman syndrome (GS) is an autosomal recessive inherited salt-losing tubulopathy (SLT). Here, we describe, for the first time, a case of GS without Gitelman-like features and with concomitant kidney stones, cysts and diabetic nephropathy (DN).

Case presentation

We described a male patient had a 19-year history of recurrent fatigue. From childhood, he had polydipsia and polyuria, paroxysmal tetany and palpitation. Serum biochemistry revealed chronic hypokalemia, metabolic alkalosis, normomagnesemia, mildly elevated Cr. Concomitant 24 h urine collection showed inappropriate renal potassium wasting, borderline hypercalciuria, moderate proteinuria consisting of major glomerular. Ultrasound of urinary tract showed bilateral and multiple kidney stones and cysts. Whole exome sequencing (WES) identified compound heterozygous mutations of SLC12A3. The unusual association of SLTs and glomerular proteinuria prompted us to perform a renal biopsy. Renal pathology showed renal involvement consistent with GS and early stage of diabetic nephropathy (DN). After treatment with KCl, magnesium oxide, perindopril and acarbose, the patient had been cured. The fatigue didn’t relapse.

Conclusion

GS had high variability of phenotype, GS may have no Gitelman-like features, kidney stones are not the exclusion criteria of GS. Renal biopsy should be warranted for GS patients with moderate to massive glomerular proteinuria.

Glomerular podocyte dysfunction in inherited renal tubular disease

BACKGROUND

Hereditary renal tubular disease can cause hypercalciuria, acid-base imbalance, hypokalemia, hypomagnesemia, rickets, kidney stones, etc. If these diseases are not diagnosed or treated in time, they can cause kidney damage and electrolyte disturbances, which can be detrimental to the maturation and development of the child. Glomerular involvement in renal tubular disease patients has only been considered recently.

METHODS

We screened 71 papers (including experimental research, clinical research, etc.) about Dent's disease, Gitelman syndrome, and cystinosis from PubMed, and made reference.

RESULTS

Glomerular disease was initially underestimated among the clinical signs of renal tubular disease or was treated merely as a consequence of the tubular damage. Renal tubular diseases affect glomerular podocytes through certain mechanisms resulting in functional damage, morphological changes, and glomerular lesions.

CONCLUSIONS

This article focuses on the progress of changes in glomerular podocyte function in Dent disease, Gitelman syndrome, and cystinosis for the purposes of facilitating clinically accurate diagnosis and scientific treatment and improving prognosis.

A case of Gitelman syndrome: our experience with a patient treated in clinical practice on a local island

Background: Gitelman syndrome (GS) is an autosomal recessive salt-losing renal tubulopathy resulting from mutations in the thiazide-sensitive Na-Cl cotransporter (NCC) gene. Notably, lack of awareness regarding GS and difficulty with prompt diagnosis are observed in clinical practice, particularly in rural settings.

Case presentation: We report a case of a 48-year-old man with GS who presented to a local clinic on a remote island. Occasional laboratory investigations incidentally revealed a reduced serum potassium level of 2.6 mmol/L. A careful medical interview revealed episodes of intermittent paralysis of the lower extremities and muscular weakness for >30 years. Subsequent laboratory investigations revealed hypomagnesemia, hypocalciuria, and hypokalemic metabolic alkalosis. Based on the patient’s history, clinical presentation, and laboratory investigations, we suspected GS. Genetic testing revealed a rare homozygous in-frame 18 base insertion in the NCC gene that might have resulted from the founder effect, consequent to his topographically isolated circumstances.

Conclusion: More case studies similar to our study need to be added to the literature to gain a deeper understanding of the functional consequences of this mutation and to establish optimal management strategies for this condition, particularly in rural clinical settings.

Gitelman Syndrome: A Rare Cause of Seizure Disorder and a Systematic Review

Gitelman syndrome is one of the few inherited causes of metabolic alkalosis due to salt losing tubulopathy. It is caused by tubular defects at the level of distal convoluted tubules, mimicking a thiazide-like tumor. It usually presents in late childhood or in teenage as nonspecific weakness, fatigability, polyuria, and polydipsia but very rarely with seizures. It is classically associated with hypokalemia, hypomagnesemia, hypocalciuria, hyperreninemia, and hyperaldosteronism. However, less frequently, it can present with normal magnesium levels. It is even rarer to find normomagnesemic patients of GS who develop seizures as the main complication since hypomagnesemia is considered the principal etiology of abnormal foci of seizure-related brain activity in GS cases. Interestingly, patients with GS are oftentimes diagnosed during pregnancy when the classic electrolyte pattern consistent with GS is noticed. Our case presents GS with normal serum magnesium in a patient, with seizures being the main clinical presentation. We also did a comprehensive literature review of 122 reported cases to show the prevalence of normal magnesium in GS cases and an overview of clinical and biochemical variability in GS. We suggest that further studies and in-depth analysis are required to understand the pathophysiology of seizures in GS patients with both normal and low magnesium levels.

A case of hypokalemia and proteinuria with a new mutation in the SLC12A3 Gene

Background

Gitelman syndrome is an autosomal recessive inherited renal disorder characterized by hypokalemia, hypomagnesemia, and hypocalciuria. Since the symptoms are not severe and laboratory results are not always clear, Gitelman syndrome can go unnoticed by physicians. Here, we report our experiences with a patient that presented with hypokalemia and proteinuria; genetic analysis revealed a new homozygous mutation in the SLC12A3 gene.

Case presentation

A 47-year-old man presented with hypokalemia and proteinuria. He had come to the hospital with the same symptoms 11 months and 3 years prior. His laboratory tests showed hypokalemia, hypocalciuria, and increased plasma angiotensin-2 activity. His renal pathology was consistent with the development of minimal lesions. Genetic analysis found a new homozygous mutation in exon 6 on the SLC12A3 gene (p.Trp281Arg) in the patient and in his brother; his mother and sister were diagnosed as heterozygous carriers of the same gene mutation. Finally, the patient was diagnosed with Gitelman syndrome.

Conclusions

This case is the first to report a homozygous mutation in the 841th nucleotide of exon 6 on the SLC12A3 gene (p.Trp281Arg), which may cause Gitelman syndrome. At the same time, this report might stimulate interest in discussing the relationship between different mutations in the SLC12A3 gene and renal pathology.

Consideration of the diagnosis of hypertension accompanied with hypokalaemia: monism or dualism?

This case report describes a 53-year-old male patient with persistent hypertension and hypokalaemia. Laboratory tests showed that the patient had hypokalaemia, hypocalcaemia and reduced urine calcium/creatinine. Levels of aldosterone and renin activity were increased significantly. Serum levels of adrenocorticotropic hormone, plasma total cortisol level, 24-h urinary-free cortisol, catecholamines, thyroid stimulating hormone and free tetraiodothyronine were normal. A novel single heterozygous mutation (c.836T> G [E6]) was found after full sequencing of the solute carrier family 12 member 3 ( SLC12A3) gene exons. The patient was diagnosed as having primary hypertension with Gitelman syndrome (GS). These findings triggered the careful consideration of whether a monistic or dualist approach to the diagnosis of this patient was the most appropriate. Monism may not always be the most appropriate approach for the diagnosis of coexistent hypertension and hypokalaemia. Consideration should be given to the possibility of the independent existence of distinct diseases (i.e. dualism) when secondary hypertension cannot be confirmed by conventional examinations and when a genetic diagnosis is crucial. As a common cause of hypokalaemia with a high level of clinical phenotypic variation, GS does not conform to the usual diagnostic criteria. It should also be noted that single heterozygous SLC12A3 gene mutations can cause disease symptoms and other genetic mutations might be involved in the pathogenesis of GS.

Genomic medicine for kidney disease

Technologies such as next-generation sequencing and chromosomal microarray have advanced the understanding of the molecular pathogenesis of a variety of renal disorders. Genetic findings are increasingly used to inform the clinical management of many nephropathies, enabling targeted disease surveillance, choice of therapy, and family counselling. Genetic analysis has excellent diagnostic utility in paediatric nephrology, as illustrated by sequencing studies of patients with congenital anomalies of the kidney and urinary tract and steroid-resistant nephrotic syndrome. Although additional investigation is needed, pilot studies suggest that genetic testing can also provide similar diagnostic insight among adult patients. Reaching a genetic diagnosis first involves choosing the appropriate testing modality, as guided by the clinical presentation of the patient and the number of potential genes associated with the suspected nephropathy. Genome-wide sequencing increases diagnostic sensitivity relative to targeted panels, but holds the challenges of identifying causal variants in the vast amount of data generated and interpreting secondary findings. In order to realize the promise of genomic medicine for kidney disease, many technical, logistical, and ethical questions that accompany the implementation of genetic testing in nephrology must be addressed. The creation of evidence-based guidelines for the utilization and implementation of genetic testing in nephrology will help to translate genetic knowledge into improved clinical outcomes for patients with kidney disease.

Gitelman syndrome: consensus and guidance from a Kidney Disease: Improving Global Outcomes (KDIGO) Controversies Conference

Gitelman syndrome (GS) is a rare, salt-losing tubulopathy characterized by hypokalemic metabolic alkalosis with hypomagnesemia and hypocalciuria. The disease is recessively inherited, caused by inactivating mutations in the SLC12A3 gene that encodes the thiazide-sensitive sodium-chloride cotransporter (NCC). GS is usually detected during adolescence or adulthood, either fortuitously or in association with mild or nonspecific symptoms or both. The disease is characterized by high phenotypic variability and a significant reduction in the quality of life, and it may be associated with severe manifestations. GS is usually managed by a liberal salt intake together with oral magnesium and potassium supplements. A general problem in rare diseases is the lack of high quality evidence to inform diagnosis, prognosis, and management. We report here on the current state of knowledge related to the diagnostic evaluation, follow-up, management, and treatment of GS; identify knowledge gaps; and propose a research agenda to substantiate a number of issues related to GS. This expert consensus statement aims to establish an initial framework to enable clinical auditing and thus improve quality control of care.