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Saudi Journal of Kidney Diseases and Transplantation
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CASE REPORT Table of Contents   
Year : 2009  |  Volume : 20  |  Issue : 2  |  Page : 274-277
Inherited renal tubular defects with hypokalemia


1 Department of Endocrinology, Medwin Hospitals, Hyderabad, India
2 Department of Nephrology, Medwin Hospitals, Hyderabad, India

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   Abstract 

Bartter's and Gitelman's syndrome are two ends of a spectrum of inherited renal tubular disorders that present with hypokalemic metabolic alkalosis of varying severity. Clinical features and associated calcium and magnesium ion abnormalities are used to diagnose these cases after excluding other commoner causes. We report on two cases, the first being a young boy, born of pregnancy complicated by polyhydramnios, who had classical dysmorphic features, polyuria, hypokalemia and hypercalciuria and was diagnosed as having Bartter's syndrome. The second patient is a lady who had recurrent tetany as the only manifestation of Gitelman's syndrome, which is an unusual presentation. Potassium replacement with supplementation of other deficient ions led to satisfactory clinical and biochemical response.

Keywords: Bartter′s syndrome, Gitelman′s syndrome, Hypokalemia

How to cite this article:
Muthukrishnan J, Modi K D, Kumar P J, Jha R. Inherited renal tubular defects with hypokalemia. Saudi J Kidney Dis Transpl 2009;20:274-7

How to cite this URL:
Muthukrishnan J, Modi K D, Kumar P J, Jha R. Inherited renal tubular defects with hypokalemia. Saudi J Kidney Dis Transpl [serial online] 2009 [cited 2018 May 21];20:274-7. Available from: http://www.sjkdt.org/text.asp?2009/20/2/274/45578

   Introduction Top


Renal tubular defects leading to hypokalemic metabolic alkalosis are an uncommon group of disorders which include Bartter's and Gitelman's syndromes. Hyper-reninemic hyper-aldostero≠nism, renal prostaglandin excess, defects in calcium and magnesium homeostasis and uri≠nary concentration ability are seen to a varying extent in patients afflicted with these disor≠ders. We herewith present two patients with the first patient having been born of a preg≠nancy complicated by polyhydramnios in the mother. He had dysmorphic features, polyuria, short stature and hypokalemia suggestive of classical Bartter's syndrome. [1] Recurrent tetany was the sole presenting manifestation in the second patient and is seen in less than 10% of cases of Gitelman's syndrome. [2],[3]


   Case History Top


Case 1

A nine-year-old boy presented with com≠plaints of polyuria (4-5 liters of urine per day), nocturia and failure to thrive, noted since five months of age. He had delayed mental and motor milestones. His elder brother had died due to an undiagnosed illness at the age of eight years. His mother had polyhydramnios during both the pregnancies. There was no history of muscle weakness, cramps, diuretic intake, excessive vomiting or diarrhea. There was no consanguinity in his parents. On eva≠luation at the age of eight months, he was detected to have hypokalemia and was advised potassium chloride replacement.

On present evaluation, his height was 118 cm (< 5th percentile, height age 7 years) and weight was 19 kg (< 5th percentile, weight age 5 years). He had normal pre-pubertal external genitalia. Blood pressure was 90/70 mmHg. Dysmorphic features in the form of triangular facies, pro≠minent nose, low set ears, high arched palate and small chin were noted. Systemic exami≠nation was normal. Investigations revealed hy≠pokalemia (serum potassium 2.0 mEq/L) and increased urinary excretion of potassium (88 mEq/L), calcium (730 mg/24hr) and magne≠sium (9 mEq/L). The serum sodium (136 mEq/ L) and magnesium levels (2.6 mg/dL) were normal. Arterial blood gas analysis showed metabolic alkalosis (pH 7.6, PaCO 2 31.4 mmHg, PaO2 110 mmHg, HCO 3 36.2 mEq/L). Plasma renin activity (supine) was 4.2 ng/mL/hour (normal 0.15-2.31) and aldosterone was 25.9 ng/dL (normal 2-16). Blood glucose level and renal function were normal. Resting electro≠cardiogram was within normal limits.

In view of polyhydramnios in the mother, growth retardation, dysmorphic features, poly≠uria, normal blood pressure, hyper-reninemic hyper-aldosteronism, hypokalemic metabolic alkalosis with high urinary potassium and calcium, in the absence of any other cause, a diagnosis of Bartter's syndrome was made. Potassium replacement with syrup potassium chloride 30 mEq per day and capsule indome≠thacin 75 mg daily was advised. On follow-up, he was growing at seven cm per year, his serum potassium was 3.3 mEq/L and bicarbo≠nate was 26 mEq/L.

Case 2

A 20-year-old girl presented with episodes of spontaneous carpopedal spasms and leg cramps since five years of age. She had been repea≠tedly treated for tetany with parenteral and oral calcium and vitamin D. One year prior to pre≠sentation, she was noted to have hypothyroidism for which levothyroxine supplementation was started. She denied history of thyroid sur≠gery, irradiation, prolonged diarrhea, vomiting, diuretic intake, hyperventilation, seizures, and symptoms suggestive of periodic paralysis. There was no similar illness in the family. On examination, trousseau's sign was positive. She was normotensive and had a diffuse grade-2, firm goiter. The remaining part of the general and systemic examination was normal. On investigation, she had hypokalemia (2.9 mEq/L), hypomagnesemia (1.5 mEq/L) and metabolic alkalosis (ABG - pH 7.55, pCO2 36.6 mm Hg, pO2 103 mmHg, HCO3 32.6 mEq/L). Spot urine sodium (175 mEq/L), potassium (36 mEq/ L) and chloride (225 mEq/L) were high. Uri≠nary potassium and magnesium excretion were 38.4 mEq/24 hours and 7.8 mEq/24 hours respectively, both being above normal limits. Urinary calcium was 110 mg/24 hours (N < 200 mg). Plasma renin activity (supine) was 3.8 ng/mL/hour (normal 0.15-2.33) and plasma aldosterone was 28 ng/dL (normal 2-16 ng/dL). Serum calcium (10.0 mg/dL), phosphorus (4.8 mg/dL) and PTH (31.3 pg/mL) were within normal limits. Resting electrocardiograph was within normal limits.

In view of hyper-reninemic hyper-aldoste≠ronism, normal blood pressure, hypokalemia, hypomagnesemia, metabolic alkalosis, high urine sodium, chloride and magnesium with normal urinary calcium with no other obvious cause, a diagnosis of Gitelman's syndrome was made. Oral potassium and magnesium supple≠ments were advised which resulted in marked symptomatic improvement. On review, she was noted to have serum potassium of 3.4 mEq/L, magnesium of 1.8 mEq/L and bicarbonate of 24 mEq/L.


   Discussion Top


Juxtaglomerular hyperplasia, hyper-reninemic hyper-aldosteronism with normal blood pre≠ssure and hypokalemic metabolic alkalosis form the major components of classic Bartter's syndrome. Gitelman's variant of this syndrome forms the other end of this spectrum which presents in late childhood or adulthood and is characterized in addition by hypomagnese≠mia. [1],[3] The pathophysiological and clinical di≠fferences between these two conditions are elaborated in [Table 1].

Hyper-reninemic hyper-aldosteronism and in≠creased potassium and hydrogen ion secretion in the collecting tubules leads to hypokalemic metabolic alkalosis in Bartter's syndrome. The renal release of vasodilator prostaglandins (PGE2 and prostacyclins) is increased which may explain normal blood pressure despite hyperaldosteronism. [4] Urinary calcium excretion is increased and plasma magnesium is within normal limits as seen in our first case. [2] Gitel≠man's syndrome is characterized by hypomag≠nesemia and normal urinary calcium excretion due to magnesium wasting in distal convoluted tubules as a result of inhibition of its uptake in the presence of hypokalemia and metabolic alkalosis as seen in the second case. [2] Muscle cramps, which are due to hypokalemia and hypomagnesemia, may be severe and are seen frequently. Urinary concentrating ability is maintained, since function of the medullary thick ascending limb is relatively intact.

The tubular defect in Bartter's or Gitelman's syndrome cannot be corrected. [5] The combi≠nation of non-steroidal anti-inflammatory drugs (NSAIDs) to reduce renal PG synthesis, and a potassium-sparing diuretic to raise the plasma potassium concentration towards normal, par≠tially reverse the metabolic alkalosis and co≠rrects the hypomagnesemia. [6],[7] The main treat≠ment for Gitelman's syndrome is lifelong magnesium and potassium supplementation.

In the first case, onset in intra-uterine period with polyhydramnios, probable occurrence of similar illness in an elder sibling, typical dys≠morphic features, growth restriction, hypoka≠lemic metabolic alkalosis with high urinary potassium, hypercalciuria and hyper-reninemic hyper-aldosteronism, in absence of any other underlying cause suggests Bartter's syndrome. The second case differed from the first one in having onset at a later age, recurrent tetany as the sole manifestation, low serum magnesium and normocalciuria.

Bartter's and Gitelman's syndrome are unco≠mmon renal tubular defects with varying deg≠rees of metabolic abnormalities. They present with hyper-reninemic hyper-aldosteronism and hypokalemic metabolic alkalosis. High index of clinical suspicion, history to rule out diu≠retic abuse and recurrent vomiting and detailed metabolic work up can clinch the diagnosis. Both the conditions respond well to replace≠ment of the deficient ion(s) and use of po≠tassium sparing diuretics. [8] Anti-prostaglandin therapy with indomethacin has an adjunctive role in these cases.

 
   References Top

1.Stein JH. The pathogenetic spectrum of Bartter's syndrome. Kidney Int 1985;28(1):85-93.  Back to cited text no. 1    
2.Cruz DN, Shaer AJ, Bia MJ, Lifton RP, Simon DB; Yale Gitelman's and Bartter's syndrome Collaborative Study Group. Gitelman's syndrome revisited: An evaluation of symptoms and health-related quality of life. Kidney Int 2001;59(2):710-7.  Back to cited text no. 2    
3.Chowta NK, Chowta MN. Gitelman's syn≠drome. Indian J Hum Genet 2006;12(1):39-40  Back to cited text no. 3    
4.Kurtz I. Molecular pathogenesis of Bartter's and Gitelman's syndromes. Kidney Int 1998; 54(4):1396-410.  Back to cited text no. 4    
5.Fujita T, Ando K, Sato Y, Yamashita K, Nomura M, Fukui T. Independent roles of prostaglandins and the renin-angiotensin sys≠tem in abnormal vascular reactivity in Bartter's syndrome. Am J Med 1982;73(1):71-6.  Back to cited text no. 5    
6.Zelikovic I. Hypokalaemic salt-losing tubulo≠pathies: An evolving story. Nephrol Dial Transplant 2003;18(9):1696-700.  Back to cited text no. 6    
7.Simon DB, Karet FE, Hamdan JM, DiPietro A, Sanjad SA, Lifton RP. Bartter's syndrome, hypokalaemic alkalosis with hypercalciuria, is caused by mutations in the Na-K-2Cl cotrans≠porter NKCC2. Nat Genet 1996;13(2):183-8.  Back to cited text no. 7    
8.Vinci JM, Gill JR Jr, Bowden RE, et al. The kallikrein-kinin system in Bartter's syndrome and its response to prostaglandin synthetase inhibition. J Clin Invest 1978;61(6):1671-82.  Back to cited text no. 8    

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Correspondence Address:
K D Modi
Department of Endocrinology, Medwin Hospitals, Chirag Ali Lane, Abids, Hyderabad-500 001
India
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PMID: 19237818

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    Tables

  [Table 1]

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    Abstract
    Introduction
    Case History
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