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

Gitelman Syndrome Provisionally Diagnosed During the First Presentation of Diabetic Ketoacidosis

Gitelman syndrome (GS) is an autosomal recessive disease characterized by hypokalemia, hypomagnesemia, metabolic alkalosis, and hypocalciuria. It is caused by mutations in gene SLC12A3 (located in chromosome 16q) encoding NaCl cotransporter. GS is usually asymptomatic for several years and is diagnosed in late childhood or adulthood. The association between GS and diabetic ketoacidosis (DKA) is rare. We present a case of a 25-year-old man with newly diagnosed diabetes mellitus and DKA with profound hypokalemia and hypomagnesemia who was provisionally found to have GS.

Gitelman syndrome in a South African family presenting with hypokalaemia and unusual food cravings

BACKGROUND

Gitelman syndrome (GS) is an autosomal recessive renal tubular disorder characterised by renal salt wasting with hypokalaemia, metabolic alkalosis, hypomagnesaemia and hypocalciuria. It is caused by mutations in SLC12A3 encoding the sodium-chloride cotransporter on the apical membrane of the distal convoluted tubule. We report a South African family with five affected individuals presenting with hypokalaemia and unusual food cravings.

METHODS

The affected individuals and two unaffected first degree relatives were enrolled into the study. Phenotypes were evaluated through history, physical examination and biochemical analysis of blood and urine. Mutation screening was performed by sequencing of SLC12A3, and determining the allele frequencies of the sequence variants found in this family in 117 ethnically matched controls.

RESULTS

The index patient, her sister, father and two aunts had a history of severe salt cravings, fatigue and tetanic episodes, leading to consumption of large quantities of salt and vinegar. All affected individuals demonstrated hypokalaemia with renal potassium wasting. Genetic analysis revealed that the pseudo-dominant pattern of inheritance was due to compound heterozygosity with two novel mutations: a S546G substitution in exon 13, and insertion of AGCCCC at c.1930 in exon 16. These variants were present in the five affected individuals, but only one variant each in the unaffected family members. Neither variant was found in any of the controls.

CONCLUSIONS

The diagnosis of GS was established in five members of a South African family through clinical assessment, biochemical analysis and mutation screening of the SLC12A3 gene, which identified two novel putative pathogenic mutations.

A severe phenotype of Gitelman syndrome with increased prostaglandin excretion and favorable response to indomethacin

Our understanding of Gitelman syndrome (GS) and Bartter syndrome has continued to evolve with the use of genetic testing to more precisely define the tubular defects responsible. GS is caused by mutations in the SLC12A3 gene encoding the Na⁺–Cl⁻ co-transporter of the distal convoluted tubule (NCCT) and tends to be associated with a milder salt-losing phenotype. We describe two female siblings presenting in infancy with a severe salt-losing tubulopathy and failure to thrive due to compound heterozygous mutations in the SLC12A3 gene encoding the NCCT. Both children were treated with indomethacin resulting in improved linear growth and polyuria. Some atypical biochemical findings in our cases are discussed including raised urinary prostaglandin (PGE2) excretion that normalized with intravenous fluid repletion.

Hypokalaemic periodic paralysis in rural northern India--most have secondary causes

Hypokalaemic periodic paralysis (HPP) is a life-threatening condition. Our aim was to study the clinical profile and laboratory parameters of HPP patients and to develop an algorithm to determine the causes of HPP. 84 patients presented with HPP over a 3 year period. 58 (69.0%) were found to have renal tubular acidosis (RTA). The other causes were idiopathic HPP (8 (9.5%)), acute gastroenteritis (4 (4.8%)), suspected primary hyperaldosteronism and familial HPP (2 each (2.4%)) and suspected Gitelman/Bartter Syndrome and thyrotoxic periodic paralysis (1 each (1.2%)). The number of cases peaks in the hot season. Over a third of the patients (35.7%) had recurrent episodes. 80% had secondary HPP and therefore a biochemical evaluation is mandatory. A simple algorithm was developed. Both health professionals and patients need further education regarding this problem in order to improve diagnosis and treatment and to improve compliance.