Gitelman syndrome

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.

Late-onset Bartter syndrome type II

Mutations in the ROMK1 potassium channel gene (KCNJ1) cause antenatal/neonatal Bartter syndrome type II (aBS II), a renal disorder that begins in utero, accounting for the polyhydramnios and premature delivery that is typical in affected infants, who develop massive renal salt wasting, hypokalaemic metabolic alkalosis, secondary hyperreninaemic hyperaldosteronism, hypercalciuria and nephrocalcinosis. This BS type is believed to represent a disorder of the infancy, but not in adulthood. We herein describe a female patient with a remarkably late-onset and mild clinical manifestation of BS II with compound heterozygous KCNJ1 missense mutations, consisting of a novel c.197T > A (p.I66N) and a previously reported c.875G > A (p.R292Q) KCNJ1 mutation. We implemented and evaluated the performance of two different bioinformatics-based approaches of targeted massively parallel sequencing [next generation sequencing (NGS)] in defining the molecular diagnosis. Our results demonstrate that aBS II may be suspected in patients with a late-onset phenotype. Our experimental approach of NGS-based mutation screening combined with Sanger sequencing proved to be a reliable molecular approach for defining the clinical diagnosis in our patient, and results in important differential diagnostic and therapeutic implications for patients with BS. Our results could have a significant impact on the diagnosis and methodological approaches of genetic testing in other patients with clinical unclassified phenotypes of nephrocalcinosis and congenital renal electrolyte abnormalities.

Identification of two novel mutations in SLC12A3 gene in two Chinese pedigrees with Gitelman syndrome and review of literature

OBJECTIVE

Gitelman syndrome (GS) is one of the most common causes of inherited hypokalaemia. As it was caused by mutations in the SLC12A3 gene, GS is a highly heterogeneous disease. Here, we aimed to investigate the clinical and genetic characteristics of two Chinese pedigrees and summarize the advance in GS genetics, diagnosis and management.

SUBJECTS AND METHODS

Two three-generation families with GS were identified and screened for mutations in the SLC12A3 gene. Genotype-phenotype correlations were analysed.

RESULTS

The two probands (A and B) were characterized by hypokalaemia, hypomagnesaemia and hypocalciuria without hypertension. Complete DNA sequencing of the SLC12A3 gene revealed two novel compound heterozygous mutations (c.179C>T and c.234delG; c.486-490delTACGGinsA and c.1925G>A), which are predicted to drastically affect normal protein structure. The female members of the pedigrees showed mild-to-no phenotype, although they carried the same mutations as the probands. Moreover, proband B presented with more severe symptoms than did proband A, which might be related to a lower serum magnesium level. During the 1-year follow-up, both probands showed satisfactory symptom improvement following the use of potassium and magnesium supplements.

CONCLUSION

Our findings strongly suggested that the two novel mutations in the SLC12A3 gene are the causative agents of GS, which may provide further insights into the function of this gene and help clinicians better understand this disorder.

A case of Gitelman syndrome with severe hyponatraemia and hypophosphataemia

Gitelman syndrome (GS) is a renal tubular disorder of the thiazide-sensitive sodium chloride cotransporter, which is located in the distal tubule of the loop of Henle. We present a rare case of GS complicated by severe hyponatraemia and hypophosphataemia. A 17-year-old boy was admitted to our institution with fever and lethargy. The workup revealed typical features of GS, i.e. hypokalaemia, hypomagnesaemia and metabolic alkalosis. In this report, we discuss the differential diagnoses and rationale for accepting GS as the most likely diagnosis. This case was complicated by severe hyponatraemia (115 mmol/L) and hypophosphataemia (0.32 mmol/L). We concluded that the syndrome of inappropriate secretion of antidiuretic hormones could not be ruled out and that respiratory alkalosis was the most likely aetiology of hypophosphataemia. This case report also generates an interesting discussion on water and electrolyte metabolism.

Gitelman syndrome manifesting in early childhood and leading to delayed puberty: a case report

INTRODUCTION

Gitelman syndrome is an inherited autosomal recessive renal salt-wasting disorder. It presents with variable clinical symptoms including muscle weakness and fatigue, and the diagnosis is based on metabolic alkalosis, hypokalemia, hypomagnesemia and hypocalciuria. It is usually diagnosed incidentally in early adulthood. There are rare cases of Gitelman syndrome presenting in early childhood; however, to the best of our knowledge it has not previously been associated with delayed puberty.

CASE PRESENTATION

A 17-year-old South Asian man with recurrent episodes of generalized muscle weakness, fatigue and cramps from the age of two years was admitted for further workup. Before the age of 12 years, the episodes had been mild, but they then got progressively worse. Other symptoms include polyuria, polydipsia, nocturia, paresthesia and occasional watery diarrhea. He also had a history of short stature, poor weight gain and delayed developmental landmarks. His family history was unremarkable except for the consanguineous marriage of his parents. An examination revealed a thin and lean man with blood pressure of 95/60mmHg. His height and weight were below the third percentile and his sexual development was at Tanner Stage II. Laboratory work revealed serum sodium of 124mmol/L, potassium 2.4mmol/L, calcium 6.5mmol/L and magnesium of 1.2mg/dL. His testosterone level was low (0.85ng/mL, normal for his age 2.67 to 10.12ng/mL) with normal levels of luteinizing hormone and follicle-stimulating hormone. The sex hormone findings were attributed to delayed puberty. A 24-hour urinary analysis revealed decreased excretion of calcium (25.9mg/24 hours). Based on the findings of hypokalemic metabolic alkalosis without hypertension, severe hypomagnesemia and hypocalciuria, a diagnosis of Gitelman syndrome was made. Treatment was started with oral supplementation of potassium, magnesium and calcium along with spironolactone and liberal salt intake.

CONCLUSION

Diagnosis of Gitelman syndrome is usually made incidentally during adolescence or early adulthood based on clinical and biochemical findings. We report that Gitelman syndrome can present during the early childhood years. If undiagnosed and untreated, it can lead to growth retardation and delayed puberty.

Chronic hypokalaemia in a hypertensive patient

Hypokalaemia in hypertensive patients is a ‘red flag’ bringing to mind various classic secondary and genetic causes related to both hypokalaemia and hypertension. We encountered a patient who had an unusual cause for his disturbance that, to our knowledge, has not been described in hypertensive patients.

Gitelman's syndrome: a pathophysiological and clinical update

Gitelman's syndrome (GS), also known as familial hypokalemic hypomagnesemia, is a rare autosomal recessive hereditary salt-losing tubulopathy, characterized by hypokalemic metabolic alkalosis, hypomagnesemia, and hypocalciuria, which is usually caused by mutations in the SLC12A3 gene encoding the thiazide-sensitive sodium chloride contrasporter. Because 18-40% of suspected GS patients carry only one SLC12A3 mutant allele, large genomic rearrangements must account for unidentified mutations. The clinical manifestations of GS are highly variable in terms of age at presentation, severity of symptoms, and biochemical abnormalities. Molecular analysis in our sibling's patients revealed compound heterozygous mutations in the coding region of SLC12A3 as underlying their disease. Such compound heterozygosity can result in disease phenotype for such loss of function mutations in the absence of homozygosis through consanguineous inheritance of mutant alleles, identical by descent. Missense mutations account for approximately 70% of the mutations in GS, and there is a predisposition to large rearrangements caused by the presence of repeated sequences within the SLC12A3. We report two adult male siblings of Jewish origin with late onset GS, who presented in their fifth decade of life with muscle weakness, hypokalemia, hypomagnesaemia, and metabolic alkalosis. Rapid clinical and biochemical improvement was achieved by replacement therapy with potassium and magnesium.

[Calcium pyrophosphate deposition disease]

Definitive diagnosis of chondrocalcinosis (CC) is allowed by identification of calcium pyrophosphate (CPP) crystals in synovial fluid. In daily practice, X-Rays are the most frequent imaging used to detect CC. Most cases of CC are sporadic. If CC occurs before 60 years of age, primary metabolic disorders such as hyperparathyroidism, hypomagnesemia, and hemochromatosis or a familial predisposition should be particularly considered. Treatment of CPP arthritis includes application of ice, rest, joint aspiration and intra-articular injection of corticosteroids. Oral NSAIDs can be used cautiously, in particular in the elderly. Prophylaxis against frequent recurrent acute CPP crystal arthritis can be achieved with low-dose oral colchicine.

Gitelman's syndrome: a rare presentation mimicking cauda equina syndrome

We describe a case of bilateral weakness of the lower limbs, sensory disturbance and intermittent urinary incontinence, secondary to untreated Gitelman's syndrome, in a 42-year-old female who was referred with presumed cauda equina syndrome. On examination, the power of both legs was uniformly reduced, and the perianal and lower-limb sensation was altered. However, MRI of the lumbar spine was normal. Measurements of serum and urinary potassium were low and blood gas analysis revealed metabolic alkalosis. Her symptoms resolved following potassium replacement. We emphasise the importance of measurement of the plasma and urinary levels of electrolytes in the investigation of patients with paralysis of the lower limbs and suggest that they, together with blood gas analysis, allow the exclusion of unusual causes of muscle weakness resulting from metabolic disorders such as metabolic alkalosis.

[Salt appetite, cramps and palpitations in a 21-year old medical secretary]

Hypokalemia is a common finding. The clinical presentation can be paralyses and cardiac arrhythmias. We present a normotensive young woman with salt appetite, cramps and palpitations. In our case report the patient shows a positive family history for hypopotassemia, a metabolic alkalosis with hypotension, and hypocalciuria with an increased urinary potassium loss. The levels of renin and aldosterone were elevated. After a negative testing for metabolites of diuretics, we obtained a positive result of the suspected SLC12A3 genetic test. This mutation leads to a failure of the thiazide-sensitive sodium-2-chloride-cotransporter, the so called Gitelman syndrome, which presents similar to a chronic thiazide therapy. The Gitelman syndrome is a rare disease with renal potassium loss and hypotension. Especially in young patients around the age of twenty or in patients with chronic intractable hypopotassemia a Gitelman syndrome should be considered.

Mechanisms for blood pressure lowering and metabolic effects of thiazide and thiazide-like diuretics

Thiazide and thiazide-like diuretics are among the most commonly used antihypertensives and have been available for over 50 years. However, the mechanism by which these drugs chronically lower blood pressure is poorly understood. Possible mechanisms include direct endothelial- or vascular smooth muscle-mediated vasodilation and indirect compensation to acute decreases in cardiac output. In addition, thiazides are associated with adverse metabolic effects, particularly hyperglycemia, and the mechanistic underpinnings of these effects are also poorly understood. Thiazide-induced hypokalemia, as well as other theories to explain these metabolic disturbances, including increased visceral adiposity, hyperuricemia, decreased glucose metabolism and pancreatic beta-cell hyperpolarization, may play a role. Understanding genetic variants with differential responses to thiazides could reveal new mechanistic candidates for future research to provide a more complete understanding of the blood pressure and metabolic response to thiazide diuretics.