A woman with red eyes and hypokalemia: A case of acquired Gitelman syndrome

Gitelman syndrome is a rare hereditary disorder of the thiazide-sensitive NaCl transporter in the distal renal tubular cells, but mimicking of such hereditary tubular disorders has been described in different autoimmune diseases (Sjögren syndrome, SLE, ...). A 62-year-old woman with painful red eyes and sicca syndrome presented at the ophthalmological department. The diagnostic evaluation identified a Sjögren syndrome with early endophthalmitis as the reason for the red eyes. Results of laboratory examination indicated severe hypokalemia, metabolic alkalosis and hypomagnesemia, although this had not been seen years earlier. Together with the urine analysis, a rare case of an acquired Gitelman syndrome was diagnosed. Substitution with potassium and magnesium improved the initial symptoms of weakness, but renal electrolyte wasting persisted even after treatment of Sjögren syndrome. In patients with autoimmune disease, laboratory analysis of serum electrolytes should be performed because different acquired tubular disorders can lead to severe hypokalemia.

Gitelman syndrome

In the past decade our understanding of the etiology and pathophysiology of Gitelman syndrome, an autosomal recessive salt-losing tubular disorder with secondary hypokalemia, has increased considerably through the achievements of molecular genetics and cell physiology. In this short review, I will summarize the most recent data on the clinical and biochemical phenotype, the molecular causes, and the pathogenesis of Gitelman syndrome. I will especially focus on the recent elucidation of the mechanisms involved in the pathogenesis of the hypomagnesemia and hypocalciuria that accompanies Gitelman syndrome.

Profound hypokalemia in diabetic ketoacidosis: a therapeutic challenge

OBJECTIVE

To describe profound hypokalemia in a comatose patient with diabetic ketoacidosis.

METHODS

We present a case report, review the mechanisms for the occurrence of hypokalemia in diabetic ketoacidosis, and discuss its management in the setting of hyperglycemia and hyperosmolality.

RESULTS

A 22-year-old woman with a history of type 1 diabetes mellitus was admitted in a comatose state. Laboratory tests revealed a blood glucose level of 747 mg/dL, serum potassium of 1.9 mEq/L, pH of 6.8, and calculated effective serum osmolality of 320 mOsm/kg. She was intubated and resuscitated with intravenously administered fluids. Intravenous administration of vasopressors was necessary for stabilization of the blood pressure. Intravenous infusion of insulin was initiated to control the hyperglycemia, and repletion of total body potassium stores was undertaken. A total of 660 mEq of potassium was administered intravenously during the first 12.5 hours. Despite such aggressive initial repletion of potassium, the patient required 40 to 80 mEq of potassium daily for the next 8 days to increase the serum potassium concentration to normal.

CONCLUSION

Profound hypokalemia, an uncommon initial manifestation in patients with diabetic ketoacidosis, is indicative of severe total body potassium deficiency. Under such circumstances, aggressive potassium repletion in a comatose patient must be undertaken during correction of other metabolic abnormalities, including hyperglycemia and hyperosmolality. Intravenously administered insulin should be withheld until the serum potassium concentration is (3)3.3 mEq/L.

Sclerochoroidal calcification associated with Gitelman syndrome and calcium pyrophosphate dihydrate deposition

Sclerochoroidal calcification is an uncommon condition. Metabolic evaluation and clinical examination are important to exclude associated systemic conditions such as the Bartter and Gitelman syndromes. It has been suggested that the lesions seen in sclerochoroidal calcification are calcium pyrophosphate dihydrate crystals. This report describes the first documented case in the UK of sclerochoroidal calcification associated with Gitelman syndrome and calcium pyrophosphate dihydrate deposition.

[62 year-old patient with rapid progressive edema, low potassium and hypertension]

A 62 year-old patient was admitted to hospital with rapid progressive edema, low potassium and hypertension. This symptoms are caused by Cushing's syndrome through ectopic paraneoplastic ACTH-production. Primary neoplasm is a small cell cancer. A Sertoli-cell-tumor of the testis was diagnosed as an additional carcinoma. Palliative chemotherapy and adrenostatic agents did not improve the clinical findings and the patient died eight weeks after admission.

Nausea, Emesis, and Muscle Weakness in a Pregnant Adolescent

BACKGROUND

Gitelman syndrome is a rare autosomal recessive disorder that presents in early adulthood with fatigue, muscle cramps and electrolyte abnormalities.

CASE

A 17-year-old African-American woman presented at 17 weeks of pregnancy with nausea, emesis, profound lower extremity proximal muscle weakness, hypokalemia, and hypomagnesemia. After a thorough evaluation, Gitelman syndrome was diagnosed. The patient was maintained on high levels of potassium and magnesium supplementation throughout the rest of her pregnancy and delivered a healthy infant.

CONCLUSION

In pregnancy, nausea and emesis is most commonly attributed to hyperemesis gravidarum. However, an atypical presentation of these symptoms and/or the coexistence of less common complaints warrant further investigation.

[Transient pseudohypoaldosteronism in infants with vesicoureteral reflux]

BACKGROUND

Congenital urologic malformations occur with an incidence of 1:100 to 1: 200, leading to an increased risk of urinary tract infections. However, most patients remain without symptoms; serious electrolyte imbalance is rare.

MATERIAL AND METHODS

We report two infants who were admitted to hospital because of failure to thrive and poor weight gain. Both children had severe hyponatraemia and hyperkalaemia. Further work-up established pseudohypoaldosteronism secondary to dilated vesicoureteral reflux and urinary tract infection. Based on a literature search in PubMed, a short overview of this rare condition is presented.

RESULTS AND INTERPRETATION

Infants younger than 6 months of age with urologic malformations, and in most cases concomitant urinary tract infections, may develop secondary pseudohypoaldosteronism. The pathogenesis of this condition is probably a result of high intrarenal pressure, inflammation and immaturity of the tubular function leading to tubular resistance to aldosterone. The major symptoms are failure to thrive, poor weight gain, and signs of dehydration. Laboratory studies show hyponatraemia, hyperkalaemia and high levels of plasma renin activity and aldosterone. Treatment involves fluid resuscitation, sodium supplementation and antibiotic treatment of concomitant urinary tract infection. The most important differential diagnosis is the salt-losing form of congenital adrenal hyperplasia. A thorough endocrinologic and urological work-up, including abdominal ultrasound examination and urine analysis, may lead to correct diagnosis and treatment.

"End-stage kidney" in longstanding bulimia nervosa

OBJECTIVE

The extent of renal damage over long-term binge/purges has not been well documented in bulimia nervosa (BN).

METHOD

We describe a 52-year-old woman with longstanding BN subsequent to an 8-year history of anorexia nervosa (AN).

RESULTS

The patient showed chaotic binge/purges and chronic severe hypokalemia after recovery from AN at age 26 years, and renal biopsy showed juxtaglomerular hyperplasia, which was diagnosed as pseudo-Bartter's syndrome.

DISCUSSION

Over the following 26 years, the patient's eating behaviors remained chaotic, and her renal function gradually deteriorated. After the patient died of pneumonia and sepsis at age 52 years, autopsy of her kidney showed chronic interstitial nephritis, proximal tubular swelling, and diffuse glomerular sclerosis, suggesting chronic glomerular injury associated with long-term binge/purges. To our knowledge, this is the first case report of a patient with BN with long-term binge/purges who developed an eventual "end-stage kidney" characterized by hypokalemic nephropathy and diffuse glomerulosclerosis.

Hypokalemia in Chinese peritoneal dialysis patients: prevalence and prognostic implication

BACKGROUND

Abnormal potassium metabolism may contribute to the increased cardiac morbidity and mortality seen in dialysis patients. We studied the pattern of serum potassium levels in a cohort of Chinese peritoneal dialysis (PD) patients.

METHODS

We studied serum potassium levels of 266 PD patients during 3 consecutive clinic visits. Dialysis adequacy, residual renal function, and nutritional status also were assessed. Patients were followed up for 33.7 +/- 20.7 months.

RESULTS

Mean serum potassium level was 3.9 +/- 0.5 mEq/L (mmol/L). Five patients (1.9%) had an average serum potassium level less than 3 mEq/L (mmol/L), whereas 54 patients (20.3%) had a serum potassium level less than 3.5 mEq/L (mmol/L). Serum potassium levels correlated with overall Subjective Global Assessment score (r = 0.276; P < 0.001) and serum albumin level (r = 0.173; P = 0.005) and inversely with Charlson comorbidity score (r = -0.155; P = 0.011). There was no correlation between serum potassium level and daily PD exchange volume, total Kt/V, urine volume, or residual glomerular filtration rate. By means of multivariate analysis with Cox proportional hazard model to adjust for confounders, serum potassium level was an independent predictor of actuarial patient survival. PD patients with hypokalemia (serum potassium < 3.5 mEq/L [mmol/L]) had significantly worse actuarial survival (hazard ratio, 1.79; 95% confidence interval, 1.12 to 2.85; P = 0.015) than those without hypokalemia after adjusting for confounding factors.

CONCLUSION

Hypokalemia is common in Chinese PD patients. Serum potassium level was associated with nutritional status and severity of coexisting comorbid condition. Furthermore, hypokalemia was an independent predictor of survival in PD patients. Additional studies may be needed to investigate the benefit of potassium supplementation for PD patients with hypokalemia.

Gitelman syndrome: genetic and expression analysis of the thiazide-sensitive sodium-chloride transporter in blood cells

Gitelman syndrome is caused by mutations of the SLC12A3 gene, which encodes the thiazide-sensitive NaCl transporter NCCT. Although several mutations causing Gitelman syndrome have been described, their molecular consequences have been rarely studied. We report a patient with Gitelman syndrome due to a mutation in the GT donor splicing site of intron 9. The analysis of RNA from peripheral blood cells showed a complete deletion of exon 9. This case report confirms the feasibility of using readily accessible blood cells to study the expression of the SLC12A3 gene, a procedure that may facilitate further studies of the functional genomics of Gitelman syndrome.

Diagnosis of a case of Gitelman's syndrome based on renal clearance studies and gene analysis of a novel mutation of the thiazide-sensitive Na-Cl cotransporter

Gitelman's syndrome is a recessively inherited renal tubular disorder characterized by low plasma potassium and magnesium levels, reduced calcium excretion, metabolic alkalosis, and increased plasma renin activity and plasma aldosterone concentration with normal blood pressure levels. A 23-yr-old man was referred to our department for further evaluation of hypokalemia. The patient also had hypomagnesemia and markedly reduced urinary calcium excretion. Renal clearance studies and gene analysis of the thiazide-sensitive Na-Cl cotransporter (TSC) were performed in the patient. In response to an iv injection of furosemide, chloride clearance (CCl) increased markedly, while distal fractional chloride reabsorption CH2O/(CH2O+CCl) was considerably reduced. In contrast, thiazide ingestion had no significant effects on these parameters. The patient had compound heterozygous mutations in the alleles encoding the TSC gene, one of which has not been formerly reported. Renal clearance studies and TSC gene analysis by amplification and direct sequencing are useful diagnostic tools for confirming a diagnosis of Gitelman's syndrome.

Approach to renal tubular disorders

The renal tubule plays an important role in fluid and electrolyte homeostasis. Renal tubular disorders may affect multiple ( e.g., Fanconi syndrome) or specific (e.g., nephrogenic diabetes insipidus, renal glucosuria) tubular functions. Most conditions are primary and monogenic but occasionally are secondary to other disorders (focal segmental glomerulosclerosis, cystinosis, Lowe syndrome). Tubular dysfunction should be considered in all children with failure to thrive, polyuria, refractory rickets, hypokalemia and metabolic acidosis. Careful clinical and laboratory evaluation is essential for appropriate diagnosis and specific management of these conditions.

Disorders of potassium

Potassium disorders are the most common electrolyte abnormality identified in clinical practice. Presenting symptoms are similar for both hypo- and hyperkalemia, primarily affecting the cardiac, neuromuscular, and gastrointestinal systems. Generally, mild hypokalemia is the most common potassium disorder seen clinically;however, severe complications can occur. Hyperkalemia is less common but more serious, especially if levels are rising rapidly. The etiologies and treatments for both hypo- and hyperkalemia are discussed, with special emphasis on the role medications play in the etiologies of each.

Electrocardiographical case. A tale of tall T's. Hyperkalaemia

A 63-year-old woman presented at the emergency department (ED) with a history of increasing lethargy and drowsiness. The electrocardiogram (ECG) showed tall peaked T waves with broadening of the QRS interval, suggestive of hyperkalaemia. This patient had an elevated serum potassium level due to diabetic ketoacidosis. She was treated with intravenous calcium chloride and insulin with 50% dextrose. The ECG changes associated with hyperkalaemia are discussed, with illustrations from a second 48-year-old male patient with renal failure who presented with malaise, lethargy and generalised weakness.

[A case of Gitelman's syndrome presenting with severe hypocalcaemia and hypokalemic periodic paralysis]

HISTORY AND CLINICAL FINDINGS

A 63-year-old woman was admitted with fatigue, general malaise, paraesthesiae, muscle cramping and weakness of the limbs. Since the age of 13, she had suffered from a transient lower extremities paralysis 3 times. Past history was unremarkable. There was no family history of disease. In addition, she denied any form of self-medication, surreptitious diuretic and laxative abuse, persistent vomiting and diarrhea. The blood pressure was 120/70 mmHg, BMI = 23.0 kg/m2, WHR = 0.84. A little anxious. The results of physical examinations were unnoticeable. The cranial-nerve functions were intact. Manual muscle tests revealed her extremities in normal condition. Sensation was normal in all modalities. The deep tendon reflexes were present but decreased mildly.

INVESTIGATIONS

Laboratory tests showed moderate to severe hypokalemia with a serum potassium concentration of 2.77 to 3.17 mmol/L, hypomagnesemia (0.31-0.35 mmol/L), hypocalcaemia (1.79-1.99 mmol/L), hypocalciuria (0.12-1.10 mmol/24 h), and metabolic alkalosis. The patient had elevated plasma renin activity and normoaldosteronism; her parathyroid hormone level was normal. Urinary calcium to creatinine ratio was (5.17-23.57) x 10(-3) mg/mg Cr. The renal clearance studies in this patient using furosemide or hydrochlorothiazide disclosed that urine volume and chloride clearance (CCL) were increased after furosemide administration, but there was no obvious change after the administration of hydrochlorothiazide. Furthermore, the distal fractional chloride reabsorption [CH2O/(CH2O+CCI)] was dramatically decreased by furosemide administration, whereas thiazide had little effect on it. These findings pointed to the presence of a non-functional thiazide-sensitive sodium/chloride cotransporter in the distal convoluted tubule, so the diagnosis of Gitelman's syndrome (GS) was made.

TREATMENT

The patient was treated with indomethacin 50 mg, tid; after 3 days, the potassium increased, but calcium and magnesium serum levels failed to improve. So triamterene 50 mg, tid was also administrated. After 4 days, the serum levels of potassium, calcium were normalized, and the serum levels of magnesium increased from 0.35 mmol/L to 0.52 mmol/L; weakness and fatigue improved markedly, the clinical symptoms disappeared. The 18-month-follow-up study found the magnesium serum level normal.

CONCLUSION

GS may be present with severe hypocalcaemia and hypokalemic periodic paralysis; the renal clearance studies by diuretic administration may be of help in diagnosing Gitelman's syndrome, and the combined use of indomethacin with triamterene has good therapeutic effect.

A case report and review of hypokalemic paralysis secondary to renal tubular acidosis

A 5-year-old girl with distal renal tubular acidosis (RTA) and hypokalemic muscle paralysis is reported. RTA is a known cause of hypokalemia, but in spite of the presence of persistent hypokalemia muscular paralysis is uncommon, rarely described in children, and the onset of paralysis may initially be misinterpreted particularly if the patient is attended by a physician who is not a pediatric nephrologist. Therefore parents must be informed about this possibility. Still, as the clinical appearance of hypokalemic paralysis is quite similar to familial hypokalemic periodic paralysis, and because the emergent and prophylactic treatment of the two disorders are quite different, we discuss the diagnostic evaluation and the treatment for both of them.

An observational study on the spectrum of heat-related illness, with a proposal on classification

During operations in subtropical areas over the summer months of 2001 and 2003 the authors audited 80 patients with heat-related illness, with the intention of defining the nature and distribution of the underlying pathophysiology. Haematological, biochemical and clinical data were gathered prospectively and patients allocated to diagnostic categories on the basis of the combination of clinical findings and investigations. Four basic types of heat-related illness could be distinguished: (1) excessive salt loss with hyponatraemic dehydration, (2) hypokalaemic alkalosis with low serum bicarbonate, (3) haemodilution associated with excessive water intake in stressed individuals, and (4) loss of normal thermoregulation, characterised by high core temperature and paradoxical cessation of sweating. Most of the patients fell clearly into a single distinct category, but there was a degree of overlap. Reduction of extracellular fluid volume was a common central mechanism. Common provoking factors identified were: gastrointestinal upset, history of previous heat intolerance (35%) environmental temperatures exceeding 45 degrees C, short period of acclimatisation (55%), travel, sleep loss, hard physical work especially if directly preceded by a period of sleep, work in confined humid spaces (45%), and lack of additional salt intake. When several of these factors were present together admission rate over one 24-hour period reached 3% of persons at risk per day. Patients are often more ill than they appear. To reduce the incidence of heat illness during future operations the following measures are proposed: 1. Avoidance of physical exertion during the heat of the day for the first 7-10 days. 2. Progressive gentle exercise in the early morning or late evening over the same period. 3. Increase in daily salt intake to 15-20gm for the first 2-3 weeks. 4. Only sufficient water intake to relieve thirst and to ensure the flow of abundant dilute urine.

Potassium Protocols

PURPOSE

The purpose of this triangulated study was to evaluate potassium protocols used in clinical practice.

RATIONALE

Hypokalemia occurs frequently in the clinical setting and can have serious consequences. It is further complicated by the fact that it has multiple causes and patient symptoms can range from asymptomatic to death. considering the complexity and potential seriousness of hypokalemia, it is important that treatment be appropriate.

DESCRIPTION OF THE PROCESS

The triangulated approach included an examination of the empirical evidence, a comparison of potassium protocols currently in use, and an evaluation of the potential benefits and risks of using a potassium protocol in a sample of patients.

OUTCOME

There is wide variation in potassium protocols and no empirical evidence in support of or opposition to these protocols. An evaluation of the use of a potassium protocol in a sample of patients indicates that patients not on protocols are not being routinely treated according to general protocol potassium replacement recommendations.

CONCLUSIONS

The use of narrowly defined potassium protocols may lead to overtreatment or incorrect treatment in the complex setting of hypokalemia.

IMPLICATIONS FOR NURSING PRACTICE

Findings suggest the need for validation of clinically significant hypokalemia, the addition of other electrolyte measures when evaluating and treating hypokalemia, and the use of routine serum potassium levels and maintenance of serum potassium levels equal to or more than 4.0 mmol/L in certain patient populations. Most important, the etiology of hypokalemia, not used in qualifying criteria on any of the potassium protocols examined, should form the basis for treatment.

[Diabetes mellitus and massive lower leg edema without heart failure]

ANAMNESIS AND CLINICAL FINDINGS

The 47-year-old male patient was admitted to the hospital because of newly diagnosed diabetes and elevated liver function tests (gamma glutamyl transferase 303 U/l). On admission the patient reported a reduction of appetite, which had increased during the past 2 weeks, fatigue, muscular weakness, polyuria and polydypsia. On physical examination the patient was moderately overweight, the blood pressure was normal. There were leg edema, which had not responded to previous treatment. There were no additional signs of right heart failure.

INVESTIGATIONS

On admission there were hypokalemia and increased parameters of cholestasis. Cortilsol concentration was elevated (1744 microg/l). Hypokalemia which was refractory to treatment raised the differential diagnosis of Conn's syndrome or ectopic secretion of ACTH, although these conditions are frequently associated with arterial hypertension. Cushing's syndrome was finally diagnosed despite of the lack of classical symptoms. Underlying reason was an adenocarcinoma of the pancreas with ectopic secretion of ACTH.

TREATMENT AND COURSE

Therapy was targeted to control the excessive secretion of cortisol. A treatment attempt with subcutaneous somatostatin and the adrenal enzyme inhibitor ketoconazole failed to control increased cortisol secretion. Bilateral surgical adrenalectomy was performed because of the patient's progressively deteriorating clinical condition. The patient developed a lethal septic shock after surgery, most likely due to the cortisol-induced immunosuppression.

CONCLUSION

1. In patients presenting with muscular weakness, leg oedema refractory to treatment, hypokalemia and hyperglycemia hypercortisolism should be ruled out even in the absence of typical clinical signs. 2. Massive hypercortisolism (as present in ectopic ACTH secretion) is not necessarily associated with arterial hypertension.

Electrocardiographical case. Young man with generalised myalgia

A 24-year-old man presented with generalised malaise and myalgia for three days. He presented to the Emergency Department after a fall at his workplace due to weakness. 12-lead electrocardiogram (ECG) showed normal sinus rhythm with ST depression in the leads V4 to V6, with a U wave. The tallest U wave appeared in V3. These ECG features are characteristic of hypokalaemia. ECG changes in hypokalaemia and differential diagnosis are discussed. A second case of thyrotoxic periodic paralysis with similar ECG changes of hypokalaemia is also presented.

Outcome of Pregnancy in a Patient with Gitelman Syndrome: A Case Report

Gitelman syndrome (GS) is an autosomal-recessive condition characterized by hypokalaemia, hypomagnesaemia and hypocalciuria. Though it affects women of child-bearing age very little information is available about its impact on maternal and fetal outcome. We describe the course of pregnancy in a patient with GS which was characterized by a sixfold increase in potassium and magnesium requirements with inability to achieve normal levels despite intravenous supplementation. There was no adverse impact on the course of pregnancy or fetal outcome. The case highlights the variability in the phenotypic presentation of GS and recommends frequent monitoring of electrolytes with supplementation guided by clinical requirements without aiming to achieve normal blood levels.

[Hypokalemic and thyrotoxic paralysis--similarities and differences]

Hypokalaemic periodic paralysis (HPP) is a rare myopathy inherited in autosomal dominantly pattern, characterized by episodic attacks of muscle weakness due to the decrease in serum potassium concentration because of ion channel's dysfunction. The thyrotoxic hypokalaemic paralysis (TPP) is an acquired form of a periodic paralysis associated directly with hyperthyroidism. HPP predominates in Caucasians, in contrast to TPP which occurs in 13-24% Asian with hyperthyroidism. Both types of hypokalaemic paralysis are similar in symptoms i.e. the sudden onset of limbs paralysis, often in the morning, after the night rest, preceded by intense exercise testing or hard work. The treatment and the prevention of TPP differs from that of HPP. Both, similarities and differences, between HPP and TPP are described in this report.

Electroenterogram manifestations and significance in hypokalemia

OBJECTIVE

To study the electroenterogram manifestations and their significance in patients with hypokalemia.

METHODS

Electroenterogram was recorded in 20 normal control subjects and 24 patients with hypokalemia using computerized electrogastroenterography.

RESULTS

The frequencies and amplitudes of the electroenterogram in patients with hypokalemia were significantly lower than those in the normal control subjects (P<0.05), and the frequencies, amplitudes and their coefficients of variation varied significantly in patients with hypokalemia before / after treatment (P<0.001).

CONCLUSION

Electroenterogram may serve as an objective means for evaluating the therapeutic effect and estimating intestinal motility of patients with hypokalemia, with also important value in predicting and diagnosing hypokalemic intestinal paralysis.

[Hypokalemic paralysis with thyrotoxicosis]

Hypokalemic periodic paralysis as a complication of thyrotoxicosis (thyrotoxic periodic paralysis) most often occurs in east Asian men. It is characterised by recurrent episodes of flaccid paralysis, hypokalemia, and underlying hyperthyroidism. It needs to be distinguished from sporadic and familial forms of periodic hypokalemic paralysis. No disturbances in the acid-base state and no extracorporal potassium loss are present. We report on the typical case of a young Chinese man presenting with hypokalemic periodic paralysis associated with yet unknown Graves' disease. Intravenous substitution of potassium and oral propranolol were administered. Complete remission was achieved after 10 hours. After medical therapy had normalised thyroid hormone levels, no further hypokalemic paralytic attacks occurred.

Hypokalaemia as a cause of recumbency in an adult dairy cow

A 3-year-old Holstein cow was presented for evaluation of recumbency. Physical examination and laboratory evaluations resulted in a diagnosis of hypokalaemia causing extreme skeletal muscle weakness. Treatment involved intravenous and oral potassium supplementation, antimicrobial and anti-inflammatory therapy, and management of recumbency using a flotation tank (the Aquacow Rise System). The cow recovered and returned to the milking herd. Multifactorial elements were identified as the cause of hypokalaemia including inappetance, treatments for ketosis and administration of dexamethasone.

Pharmacotyping of hypokalaemic salt-losing tubular disorders

Long standing confusion exists in the terminology of hypokalaemic salt-losing tubulopathies (SLTs). SLTs are autosomal recessively transmitted and characterized by normotensive secondary hyperreninism/hyperaldosteronism with hypokalaemic metabolic alkalosis. Historically, four phenotypical variants have been described: (1) the (classic) Bartter syndrome (cBS), (2) the hypomagnesaemic hypocalciuric Gitelman syndrome (GS), (3) the hypercalciuric hyperprostaglandin-E-syndrome (HPS) or antenatal Bartter syndrome (aBS) and (4) the hyperprostaglandin-E-syndrome with sensorineural deafness (HPS + SND). The latter two syndromes are the most severe variants with antenatal manifestation with polyhydramnios and life-threatening course of salt- and water-loss. Defects in five renal membrane proteins involved in electrolyte reabsorption have been identified: In HPS-patients mutations in (1) either the furosemide-sensitive sodium-potassium-chloride cotransporter NKCC2, or (2) in the potassium channel ROMK have been identified, and (3) HPS + SND is caused by mutations in the beta-subunit of the chloride channels ClC-Kb and -Ka (named barttin), all mimicking the major pharmacological effects of furosemide with minor potassium-wasting in ROMK-patients as seen in patients treated with simultaneous furosemide and amiloride, and minor calcium-wasting in Barttin-patients resembling the combination of furosemide and thiazides. (4) cBS is caused by mutations in the chloride channel ClC-Kb with similar clinical characteristics as seen under combination of thiazides and furosemide, (5) GS is caused by mutations in the thiazide-sensitive sodium-chloride cotransporter NCCT resembling the effect of long-term thiazide administration.

CONCLUSION

The combination of pharmacology and genetics suggests a new terminology for the above described SLTs: Furosemide-like-SLT for HPS caused by NKCC2-mutations, furosemide/amiloride-like-SLT for HPS caused by ROMK-mutations, furosemide/thiazide-like-SLT for HPS + SND, thiazide/furosemide-like-SLT for cBS, and thiazide-like-SLT for GS.

Electrocardiographic manifestations: electrolyte abnormalities

Because myocyte depolarization and repolarization depend on intra- and extracellular shifts in ion gradients, abnormal serum electrolyte levels can have profound effects on cardiac conduction and the electrocardiogram (EKG). Changes in extracellular potassium, calcium, and magnesium levels can change myocyte membrane potential gradients and alter the cardiac action potential. These changes can result in incidental findings on the 12-lead EKG or precipitate potentially life-threatening dysrhythmias. We will review the major electrocardiographic findings associated with abnormalities of the major cationic contributors to cardiac conduction-potassium, calcium and magnesium.

Laboratory tests to determine the cause of hypokalemia and paralysis

BACKGROUND

Hypokalemia and paralysis may be due to a short-term shift of potassium into cells in hypokalemic periodic paralysis (HPP) or due to a large deficit of potassium in non-HPP. Failure to make a distinction between HPP and non-HPP may lead to improper management. Therefore, we evaluated the diagnostic value of spot urine tests in patients with hypokalemia and paralysis during 3 years.

METHODS

Before therapy, the urine potassium concentration, potassium-creatinine ratio, and transtubular potassium concentration gradient were determined in a second voided urine sample.

RESULTS

Forty-three patients with hypokalemia and paralysis were identified: 30 had HPP and 13 had non-HPP. There was no significant difference in the plasma potassium or bicarbonate concentrations and in the pH of arterial blood between the 2 groups. All but 2 patients in the non-HPP group had urine potassium concentration values less than 20 mmol/L. Although the potassium concentration was significantly lower in the HPP group, there was some overlap. In contrast, the transtubular potassium concentration gradient and potassium-creatinine ratio differentiated patients with HPP vs non-HPP. Although only a mean +/- SD of 63 +/- 36 mmol of potassium chloride was administered in the patients with HPP, rebound hyperkalemia (>5 mmol/L) occurred in 19 (63%) of these 30 patients.

CONCLUSIONS

Calculating the transtubular potassium concentration gradient and potassium-creatinine ratio provided a simple and reliable test to distinguish HPP from non-HPP. Minimal potassium chloride supplementation should be given to avoid rebound hyperkalemia in patients with HPP.

[Potassium in renal disease]

BACKGROUND

Hypokalemia and hyperkalemia are among the most common disturbances of the electrolyte status.

PATIENTS AND RESULTS

Since the regulation of the potassium homeostasis depends on normal renal function, patients with acute or chronic renal disease tend to develop such disturbances. The clinical consequences of hypokalemia or hyperkalemia are often severe and unforeseen, which is illustrated by respective case reports in this paper.

CONCLUSION

Due to the often severe clinical consequences of hypokalemia or hyperkalemia, these electrolyte disturbances deserve special diagnostic and therapeutic attention.