Comparison of clinical features in Gitelman syndrome patients with different urinary calcium excretion / 中华肾脏病杂志

ABSTRACT

Objective:To observe the clinical features in Gitelman syndrome (GS) patients with different urinary calcium excretion, and investigate the value of urinary calcium excretion in the clinical classification for GS.Methods:GS cases from the National Rare Diseases Registry System of China (NRSC) (2016-2018) with SLC12A3 gene screened in Peking Union Medical College Hospital were collected. The features of urinary calcium excretion were analyzed, and the phenotypes of patients with hypocalciuria were compared to those without. Hydrochlorothiazide (HCT) test was performed according to the standard process, and the maximal increment of chloride excretion fraction (&Delta;FECl) was calculated. Results:A total of 83 GS patients were included, among whom 53 (63.86%) patients had hypocalciuria. The ratio of urinary calcium/creatine was significantly lower in patients with hypocalciuria compared to those without [(0.085±0.058) mmol/mmol vs (0.471±0.284) mmol/mmol, t=7.349, P<0.001]. Age, gender, estimated glomerular filtration rate, blood pressure, serum and urinary electrolytes, and alkalosis were all comparable between groups. Fatigue ( χ2=4.595, P=0.032) and polyuria ( χ2=5.778, P=0.016) were less frequently reported in hypocalciuria patients, while all the other clinical symptoms were comparable. Sixteen patients in each group underwent HCT test, and the median value of &Delta;FECl was comparable between patients with and without hypocalciuria [0.539%(0.430%, 1.283%) vs 0.829% (0.119%,1.298%), U=130.000, P=0.956], both of which indicated no response to HCT. Conclusions:The proportion of low urinary calcium in GS patients is 63.86%. There is no definite relationship between urinary calcium excretion, phenotype and the extent of NCC dysfunction.