Functional expression of mutations in the human NaCl cotransporter: evidence for impaired routing mechanisms in Gitelman's syndrome.
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Gitelman's syndrome is an autosomal recessive renal tubular disorder characterized by hypokalemic metabolic alkalosis, hypomagnesemia, and hypocalciuria. This disorder results from mutations in the thiazide-sensitive NaCl cotransporter (NCC). To elucidate the functional implications of mutations associated with this disorder, metolazone-sensitive (22)Na(+) uptake, subcellular localization, and glycosidase-sensitive glycosylation of human NCC (hNCC) were determined in Xenopus laevis oocytes expressing FLAG-tagged wild-type or mutant hNCC. Injection of 10 ng of FLAG-tagged hNCC cRNA resulted in metolazone-sensitive (22)Na(+) uptake of 3.4 +/- 0.2 nmol Na(+)/oocyte per 2 h. Immunocytochemical analysis revealed sharp immunopositive staining at the plasma membrane. In agreement with this finding, a broad endoglycosidase H-insensitive band of 130 to 140 kD was present in Western blots of total membranes. The plasma membrane localization of this complex-glycosylated protein was confirmed by immunoblotting of purified plasma membranes. The mutants could be divided into two distinct classes. Class I mutants (G439S, T649R, and G741R) exhibited no significant metolazone-sensitive (22)Na(+) uptake. Immunopositive staining was present in a diffuse band just below the plasma membrane. This endoplasmic reticulum and/or pre-Golgi complex localization was further suggested by the complete absence of the endoglycosidase H-insensitive band. Class II mutants (L215P, F536L, R955Q, G980R, and C985Y) demonstrated significant metolazone-sensitive (22)Na(+) uptake, although uptake was significantly lower than that obtained with wild-type hNCC. The latter mutants could be detected at and below the oocyte plasma membrane, and immunoblotting revealed the characteristic complex-glycosylated bands. In conclusion, this study substantiates NCC processing defects as the underlying pathogenic mechanism in Gitelman's syndrome. (+info)
Thyrotoxic hypokalemic periodic paralysis in a Hispanic male.
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We report a case of a Hispanic male presenting with acute onset of bilateral lower extremity weakness, without any antecedent viral or bacterial illness, dietary changes, infiltrative orbitopathy, diffuse goiter, infiltrative dermopathy, and family history of periodic paralysis, who was later found to have Graves' disease. This demonstrates a rare case of periodic paralysis as the initial presentation of hyperthyroidism. Thyrotoxic hypokalemic periodic paralysis is common in Asian and Hispanic individuals and uncommon in whites and African Americans. (+info)
Life-threatening hypokalaemia and quadriparesis in a patient with ureterosigmoidostomy.
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We report quadriparesis as a result of severe hypokalaemia and acidosis in a 50-year-old man who had undergone ureterosigmoidostomy for bladder extrophy 48 years earlier. Aggressive suppletion with intravenous potassium and bicarbonate combined with potassium-sparing diuretics and ACE inhibitors resulted in complete restoration of the serum potassium and resolution of the neurological symptoms. The underlying mechanism as well as the treatment of hypokalaemia and hyperchloraemic metabolic acidosis after ureterosigmoidostomy are briefly discussed. (+info)
Electrocardiogram with prolonged QT interval in Gitelman disease.
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BACKGROUND: Potassium and magnesium deficiency prolong the QT interval on a standard electrocardiogram and predispose the patient to dangerous cardiac arrhythmias. No information is available on QT interval in patients diagnosed with Gitelman disease. METHODS: The QT interval was assessed on lead II in 27 patients with biochemically and genetically defined Gitelman disease, who had discontinued medical treatment for at least four weeks. They included 15 female and 12 male subjects, aged 6.7 to 40 years old, median 20 years old. The corrected QT interval was calculated from the measured QT interval and heart rate using the Bazett formula. RESULTS: The corrected QT interval was normal (between 391 and 433 msec) in 16 and prolonged in the remaining 11 patients (between 444 and 504 msec). Patients with prolonged and patients with normal QT interval did not significantly differ with respect to female to male ratio, plasma potassium, plasma total magnesium, and plasma ionized calcium. Plasma sodium and chloride values were slightly but significantly lower and bicarbonate levels higher in patients with a prolonged than in those with a normal QT interval. CONCLUSIONS: The corrected QT interval is often pathologically prolonged in patients with Gitelman disease, suggesting that there is an increased risk for development of dangerous arrhythmias. Further investigations are required in patients with a prolonged QT interval to assess the true hazard of dangerous arrhythmias. (+info)
Lactic acidosis associated with the usual theophylline dose in a patient with asthma.
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Metabolic and electrolyte abnormalities, including hypokalemia, hyperglycemia and lactic acidosis, are associated with theophylline overdose. However, we report an unusual case of sinus tachycardia, lactic acidosis, hypokalemia and hyperglycemia associated with the usual theophylline dose in a patient with asthma. The theophylline dose was 200 mg orally twice daily. Three hours after administration of the third dose, the patient experienced palpitation. An electrocardiogram showed a sinus tachycardia. Arterial blood gas analysis revealed a mixed metabolic acidosis and respiratory alkalosis. Serum lactate level was 51 mmol/L (normal 0.7-2.1 mmol/L). Biochemistry results were sodium 136 mEq/L, chloride 99 mEq/L, potassium 1.9 mEq/L and glucose 204 mg/dL. Our case suggests that a possibility of theophylline-associated metabolic abnormalities should be considered when an asthmatic patient given the usual theophylline dose presents with lactic acidosis, hypokalemia and hyperglycemia of unknown etiology. (+info)
A randomized, double-blind, placebo-controlled trial of acetazolamide for the treatment of elevated intracranial pressure in cryptococcal meningitis.
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We conducted a trial of oral acetazolamide for the treatment of cryptococcal meningitis in 22 Thai adults with headache and an opening cerebrospinal fluid pressure of >/=200 mm H(2)0. The trial was terminated prematurely because patients who received acetazolamide developed significantly lower venous bicarbonate levels and higher chloride levels and had more-frequent serious adverse events than did subjects who received placebo. (+info)
Severe hypokalaemia in a Chinese male.
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A 34-year-old Chinese man developed acute, severe, generalized muscle weakness while mountain climbing. In the Emergency Department that morning, the most striking abnormalities were flaccid paralysis of both upper and lower limbs and a plasma potassium (K+) concentration (P(K)) of 1.7 mmol/l. To explain the basis for this constellation of findings, an imaginary consultation was sought with Professor McCance, the legendary integrative physiologist. Using both a deductive and a quantitative analysis, he illustrated that a simple story of an acute shift of K+ into cells was not sufficient to explain the patient's hypokalaemia. The clue he used to suspect a large total body deficit of K+ was a higher than expected rate of K(+) excretion on the initial spot urine (higher than expected ratio of K+: creatinine in the urine). This interpretation was supported by the fact that the patient needed a large supplement of K(+) to raise his P(K) to just under 3 mmol/l. It was only after more detailed studies based on urine chemistry that an accurate diagnosis and effective treatment could be instituted. The final question was why one of the hallmarks of the diagnosis of hyperaldosteronism (hypertension) was absent, yet hypokalaemia was so severe. (+info)
Variant of pre-clinical Cushing's syndrome: hypertension and hypokalemia associated with normoreninemic normoaldosteronism.
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The case of a 48-year-old woman with a left adrenocortical adenoma and showing hypokalemia, hypertension and normoreninemic normoaldosteronism is reported. Basal plasma adrenocorticotrophic hormone (ACTH) and cortisol levels were within the reference ranges. The patient's plasma cortisol level decreased insufficiently at night, and was insufficiently decreased by nighttime administration of dexamethasone. She showed no Cushingnoid stigmata. Iodocholesterol scintigraphy revealed tumor-sided uptake alone. The plasma dehydroepiandrosterone-sulfate level was low-to-normal for her age. Metabolic alkalosis and increased potassium clearance after sodium thiosulfate loading were revealed. The plasma aldosterone level was within the normal range, but it was statistically higher than the range for patients with pre-clinical Cushing's syndrome. However, peripheral plasma renin activity (PRA) increased normally after the patient resumed an upright posture following furosemide administration. After adenomectomy the hypokalemia and hypertension were resolved, and the plasma ACTH, cortisol, and PRA remained within the reference ranges. The plasma aldosterone level decreased slightly, but also remained within the reference range after adenomectomy. Paradoxical hyperplasia in the non-neoplastic adrenal glomerulosa zone, which indicates primary aldosteronism, and slight atrophy of the non-neoplastic adrenal cortex, which indicates pre-clinical Cushing's syndrome, were demonstrated. These findings satisfied the criteria of pre-clinical Cushing's syndrome, but did not completely satisfy those of primary aldosteronism. However, the level of CYP11 B2 mRNA in the tumor was in the lower-limit of the range for adenomas associated with primary aldosteronism and was higher than the ranges for adenomas associated with pre-clinical Cushing's syndrome and overt Cushing's syndrome. Based on these results, this case was suspected to constitute a variant of pre-clinical Cushing's syndrome with slight hypersecretion of aldosterone. (+info)