A family with liddle's syndrome caused by a mutation in the beta subunit of the epithelial sodium channel

Liddle's syndrome is a rare form of autosomal-dominant salt-sensitive hypertension. Constitutive activation of the amiloride-sensitive distal renal epithelial sodium channel (ENaC) is essential for salt-sensitive hypertension. Recently, several DNA analysis studies have indicated that there is a mutation of C-terminus of either the beta or y subunit. We sequenced the C-termini of the beta and -gamma subunits of the ENaC in a Japanese family with hypertension and hypopotassemia without excess minerarocorticoids, clinically diagnosed as Liddle's syndrome. The mutation of the ENaC of this family was beta R564X. Since such case seem to be rare in the literature, detailed data are shown in this report.

Sclerochoroidal calcification: clinical manifestations and systemic associations

BACKGROUND

Sclerochoroidal calcification is an unusual ocular condition that is believed to be idiopathic in most cases.

OBJECTIVES

To describe the clinical manifestations of sclerochoroidal calcification and to investigate its possible systemic associations.

METHODS

This noncomparative consecutive case series included patients diagnosed as having sclerochoroidal calcification based on clinical characteristics and diagnostic test findings. We analyzed the demographic, systemic, and ocular features of 27 such patients. Systemic evaluation included tests for calcium-phosphorus metabolism in 19 patients and renal tubular hypokalemic metabolic alkalosis syndromes (Bartter or Gitelman syndrome) in 13.

RESULTS

All the patients were asymptomatic older (mean age, 70 years) white individuals, incidentally noted as having a choroidal lesion on routine examination. Among 38 eyes, the main referral diagnoses were choroidal metastasis in 10 eyes (26%), choroidal melanoma in 8 (21%), and choroidal nevus in 4 (11%). Sixteen patients (59%) had unilateral clinical findings, while 11 (41%) had bilateral. The Snellen visual acuity was 20/50 or better in 37 eyes (97%). Cogan scleral plaque was visible anterior to the insertion of horizontal rectus muscles in 10 eyes (26%). Among 77 foci, there were a mean of 2 foci of sclerochoroidal calcification in each eye, 41 yellow (53%), 32 yellow-white (42%), 2 white (3%), and 2 orange (3%), measuring a mean 2.6 mm in diameter and 1.1 mm in thickness. The most common locations were postequatorial in 45 (58%), along the temporal vascular arcades in 30 (39%), and in the superotemporal quadrant in 43 (56%). A-scan and B-scan ultrasonography revealed dense echoes compatible with calcium, with orbital shadowing. All the lesions remained stable in size and configuration during a mean follow-up of 38 months. One patient developed a choroidal neovascular membrane over the area of sclerochoroidal calcification. Investigations for abnormal calcium-phosphorus metabolism in 19 patients revealed primary hyperparathyroidism in 1 patient (5%). Clinical and biochemical evaluation of 13 patients demonstrated hypomagnesemia in 6 (46%). Four patients (31%) met the criteria for the diagnosis of Gitelman syndrome.

CONCLUSIONS

Sclerochoroidal calcification usually manifests as multiple discrete yellow placoid lesions in the midperipheral fundus of asymptomatic older white individuals. Although most cases may be idiopathic in nature, some patients may have underlying systemic disorders involving abnormal calcium-phosphorus metabolism or renal tubular hypokalemic metabolic alkalosis syndromes. All patients with sclerochoroidal calcification should be tested for these treatable systemic associations.

Potassium status of Northeast Thai constructors in three different geographic locations

Sudden and unexpected death of young adults during sleep is a phenomenon among Southeast Asians and particularly young Northeast (NE) Thailand constructors in Singapore. Survivor of sudden unexplained death syndrome (SUDS) without structural heart disease with idopathic ventricular fibrillation (VF) has been documented. Low plasma potassium (K) and depletion of K can occur simply through a reduction of K intake and are associated with increased risk of VF. The K-status of the populations was evaluated in the NE (Group 1, n=30), Bangkok (Group 2, n=48) and Singapore (Group 3, n=46). Groups 2 and 3 were further subdivided into Group 2A (worked in Bangkok < or = 1 year, n=8), Group 2B (worked in Bangkok > 1 year, n=40), Group 3A (consumed self-prepared or ready-to-buy meals, n=25) and Group 3B (regularly consumed foods provided free-of-charge by construction companies, n=21). Thirty-four male healthy university personnels from the NE and Bangkok served as the control--Group 4. Two 24-h urine samples and a fasting blood sample were collected from each subject. Dietary-K from food was determined by duplicated meal analysis. All these samples were then analyzed for their K-content. Group 3A had the lowest K-status: their K-intake, serum-K, and urinary-K level were 29 +/- 5.8 mmol/day (% low K-intake=100), 3.43 +/- 0.34 mmol/L (% hypokalemia=48) and 19.23 +/- 8.2 mmol/day (% hypokaliuria=87.5), respectively. Among the construction workers, average K-intake, serum-K and urinary-K levels were 45.5 +/- 6.1 mmol/day (% low K-intake = 37.5), 3.93 +/- 0.2 mmol/L (% hypokalemia = 2.5) and 39.6 +/- 9.2 mmol/day (% hypokaliuria = 12.5), respectively. The values of Group 2B were similar to Group 4. In addition, when the data from all of the groups were compared, there was a positive correlation between dietary-K (intake) and urinary-K (excretion) (r=0.881, p<0.001). In conclusion, NE Thailand constructors from various locations exhibited low K status with low dietary-K, high incidence of hypokalemia, and low urinary-K. From the present study, this low K status may be an important trigger factor for VF in construction workers and associated with increase risk of SUDS.

[Pseudo-Gitelman's syndrome as consequence of loop diuretics abuse]

We describe a case of 40-year old patient with chronic, resistant to treatment hypokalaemia. Differential diagnosis of renal potassium loss among Gitelman's syndrome, Bartter's syndrome and loop diuretic abuse was made.

Hypokalemia, metabolic alkalosis, and hypertension: Cushing's syndrome in a patient with metastatic prostate adenocarcinoma

Ectopic adrenocorticotropic hormone (ACTH) and/or corticotropin-releasing hormone (CRH) are associated with a growing list of tumors. We report a 69-year-old white man with a history of high-grade prostate carcinoma and widely metastatic adenocarcinoma who presented with metabolic alkalosis, hypokalemia, and hypertension secondary to ectopic ACTH and CRH secretion. Laboratory values were consistent with hypokalemia and metabolic alkalosis. Markedly elevated serum cortisol (135 microg/dL), ACTH (1,387 pg/dL), CRH (69 pg/dL), and urine free cortisol (16,276 microg/24 h) levels were found. Chest computed tomographic (CT) scan showed small noncalcified parenchymal densities; however, bronchoscopy and bronchoalveolar lavage washings were unremarkable for a neoplastic process. Abdominal CT scan and magnetic resonance imaging showed multiple small liver lesions and multiple thoracic and lumbar intensities consistent with diffuse metastatic disease. Histological analysis of a biopsy specimen from the thoracic spine showed an undifferentiated adenocarcinoma consistent with a prostate primary tumor. The severe metabolic alkalosis secondary to glucocorticoid-induced excessive mineralocorticoid activity was treated with potassium supplements, spironolactone, and ketoconazole. In this case report, we describe an unusual tumor associated with ectopic ACTH and CRH production and the pharmacodynamic relationship of plasma cortisol levels and urinary cortisol excretion with ketoconazole treatment.

Polymorphic ventricular tachycardia in a woman taking cesium chloride

A 47-year-old patient presented with syncope and recurrent episodes of polymorphic ventricular tachycardia. She had evidence of prolonged QT interval by ECG and had been taking cesium as a dietary supplement. Correction of the hypokalemia and discontinuation of the cesium resulted in normalization of the QT interval during follow-up with no further recurrence of ventricular arrhythmias. The use of this drug is potentially hazardous as it may induce fatal ventricular arrhythmias.

Systemic lupus erythematosus presenting initially as hydrogen ATPase pump defects of distal renal tubular acidosis

Tubulointerstitial involvement is well recognized in systemic lupus erythematosus. The tubular dysfunction is usually latent and usually presents after diagnosis of systemic lupus erythematosus. We report a case presenting that she is well previously and initially diagnosed as periodic paralysis of hypokalemia at emergency room and final diagnosis is systemic lupus erythematosus with H+-ATPase pump defect of distal type renal tubular acidosis. Kidney biopsy showed lupus nephritis classified as mesangial proliferative glomerulonephritis WHO class II B. Her renal tubular acidosis was subsided after steroid therapy was administered.

Sixty-eight-year-old patient with hypokalemia

A 68-year-old patient with severe hypokalemia and metabolic alkalosis is described. Six years before admission he had been treated for a small cell bronchial carcinoma. We discuss the diagnostic approach of hypokalemia and the way in which we reached the diagnosis. The patient suffered from metastatic small cell carcinoma with a very high plasma adrenocorticotropic hormone concentration, possibly due to production of corticotropin-releasing hormone by the malignancy.

[Quadriplegia secondary to potassium depletion]

Muscle paralysis due to potassium depletion are unusual. We report the case of a patient who developed quadriplegia and language disorders due to potassium depletion, following large intestinal resection. Potassium supplementation was given intravenously at a rate of 0.25 mmol.kg-1.h-1 during the first 48 h. This allowed complete total and rapid recovery from the paralysis.

Mimicry of surreptitious diuretic ingestion and the ability to make a genetic diagnosis

Gitelman's syndrome, also known as "hypocalciuric variant of Bartter's syndrome", is a cause of chronic hypokalemia and hypomagnesemia in adults. A specific gene has been found responsible for this disorder, encoding the thiazide-sensitive NaCl coporter (TSC) in the distal convoluted tubule. We describe a psychiatric patient with chronic symptomatic hypokalemia and hypomagnesemia whose electrolyte disturbances were subsequently misdiagnosed as an acute alcohol and benzodiazepine withdrawal syndrome, as chronic diuretic abuse and as a classical Bartter's syndrome. Finally, genetic investigation revealed the presence of mutations in the SLC12A3 gene leading to the proper diagnosis of Gitelman's syndrome. We emphasize that Gitelman's syndrome should be suspected in every hypokalemic patient with biochemical resemblance of diuretic ingestion, especially when repeated toxic screens for diuretics are negative. The ability to make a molecular-genetic diagnosis can be of practical benefit in confusing clinical settings.

[Genetic hypokalemia]

INTRODUCTION

Hypokalemia is the most frequent electrolytic disturbance in hospitalized patients. It is sometimes familial. Careful clinical and biological evaluation may guide further genetic analysis.

CURRENT KNOWLEDGE AND KEY POINTS

Genetic hypokalemia is linked to disorders of mineralocorticoid hormone synthesis or action (glucocorticoid-remediable hyperaldosteronism, congenital adrenal hyperplasia, apparent excess of mineralocorticoids), to renal tubular disorders (Liddle's syndrome, Bartter's and Gitelmann's syndrome, tubular acidosis) or to disorders of cellular transfer of potassium (hypokalemic periodic paralysis).

FUTURE PROSPECTS AND PROJECTS

Molecular mechanisms of adult Bartter's syndrome are probably different from pediatric syndromes. A better clinical and biological evaluation with longitudinal follow-up could allow significant progress in the knowledge of the natural history and prognosis of these syndromes.

Systemic lupus erythematosus presenting initially as hydrogen ATPase pump defects of distal renal tubular acidosis

Tubulointerstitial involvement is well recognized in systemic lupus erythematosus. The tubular dysfunction is usually latent and usually presents after diagnosis of systemic lupus erythematosus. We report a case presenting that she is well previously and initially diagnosed as periodic paralysis of hypokalemia at emergency room and final diagnosis is systemic lupus erythematosus with H+-ATPase pump defect of distal type renal tubular acidosis. Kidney biopsy showed lupus nephritis classified as mesangial proliferative glomerulonephritis WHO class II B. Her renal tubular acidosis was subsided after steroid therapy was administered.

[Gitelman syndrome: a rare cause of hypokalemia]

We report a case of hypokaliemia whose origin is a urinary potassium loss associated with syndrome of Gitelman. The syndrome of Gitelman is a rare familiar autosomal recessive nephropathy. We will discuss the pathophysiology of this syndrome and differential diagnoses.

Nephrocalcinosis and renal cysts associated with apparent mineralocorticoid excess syndrome

Apparent mineralocorticoid excess (AME) syndrome is a rare inherited disorder caused by 11beta-hydroxysteroid dehydrogenase (11-HSD 2) isozyme deficiency in the kidney. This enzyme is responsible for oxidizing cortisol to its inactive metabolite cortisone. An elevated tetrahydrocortisol (THF) and allotetrahydrocortisol (aTHF) to tetrahydrocortisone (THE) ratio in the urine is pathognomonic of AME syndrome. Clinical features include hypertension, hypokalemia, alkalosis, reduced plasma renin activity (PRA), low aldosterone levels, and occasionally nephrocalcinosis. Here we describe a 13-year-old boy who presented with severe hypertension, hypokalemia, low PRA and aldosterone levels, and elevated THF plus aTHF/THE ratio in the urine consistent with a diagnosis of AME syndrome. On ultrasound examination, he had severe nephrocalcinosis, and bilateral renal cysts. Renal cysts have not been previously reported in AME syndrome. The development of nephrocalcinosis and renal cysts may be associated with chronic long-standing hypokalemia. An early diagnosis and treatment of AME syndrome could help to prevent these sequelae, and to preserve renal function.

Urinary sodium, potassium, chloride, calcium, magnesium, phosphate, urate and urea in healthy subjects aged 5-18 years

The determination of urinary electrolytes is helpful in the diagnosis of children with dyselectrolytemia or metabolic acid-base imbalance of unknown origin [1–3]. The urinary excretion of electrolytes has mostly been evaluated by investigating 24-hour urine specimens [4]. The collection of such urine samples is laborious in children without bladder control, in those unable to comply while playing or at school, or in those with acute electrolyte abnormalities. The usefulness of measuring urinary solutes in relation to creatinine in urine has been suggested [5].