Supplementary Material for: Clinical Severity of Gitelman Syndrome Determined by Serum Magnesium

Background/Aims: Normomagnesemia is considered atypical in Gitelman syndrome (GS). Here, we describe clinical, pathological and genetic characteristics in Chinese GS patients with or without hypomagnesemia in order to determine whether serum magnesium concentration indicates the severity of the disease. Methods: 7 normomagnesemic and 25 hypomagnesemic GS patients who were confirmed by direct sequencing of SLC12A3 gene were included. Clinical manifestation and laboratory tests were documented. Supine and upright plasma renin activity, angiotensin II and aldosterone were determined by radioimmunoassay. Transient receptor potential channel melastatin subtype 6 (TRPM6) was detected by immunohistochemistry in paraffin-embedded renal biopsy sections of 12 GS patients. 14 patients with glomerular minor lesion served as controls. The distribution of the mutations on the predicted NCC protein was analyzed and compared between two subgroups. Results: Clinical manifestations, electrolyte abnormalities, metabolic alkalosis and renin-angiotensin-aldosterone system activation were found to be milder in normomagnesemic compared with the hypomagnesemic group. Compared with glomerular minor lesion controls, the TRPM6-positive area was significantly decreased in hypomagnesemic patients (4.96 ± 1.88 vs. 8.63 ± 2.67%) while it was near normal (7.82 ± 5.23%) in 2 normomagnesemic GS patients. A higher percentage of intracellular mutations was observed in normomagnesemic patients than hypomagnesemic patients (92.31 vs. 56.52%, p = 0.02). Conclusions: Normomagnesemia is not rare in GS. Serum magnesium may indicate the severity of GS.

背景与目的：吉特曼综合征（Gitelman syndrome, GS）患者出现正常镁血症被认为是非典型表现。本研究对伴或不伴低镁血症的中国吉特曼综合征患者的临床、病理及遗传学特征进行分析，旨在明确血清镁浓度是否可反映疾病严重程度。方法：本研究纳入经SLC12A3基因直接测序确认的7例正常镁血症型及25例低镁血症型GS患者，记录其临床表现与实验室检查结果。采用放射免疫法检测卧位与立位血浆肾素活性、血管紧张素Ⅱ及醛固酮水平。对12例GS患者的石蜡包埋肾活检组织进行免疫组化检测，以分析瞬时受体电位阳离子通道亚家族M成员6（transient receptor potential channel melastatin subtype 6, TRPM6）的表达情况；另以14例肾小球轻微病变患者作为对照。对两个亚组中预测的NCC蛋白上的突变分布情况进行分析与比较。结果：与低镁血症组相比，正常镁血症组患者的临床表现、电解质紊乱、代谢性碱中毒及肾素-血管紧张素-醛固酮系统激活程度均更轻微。与肾小球轻微病变对照组相比，低镁血症型GS患者的TRPM6阳性区域占比显著降低（4.96±1.88 vs 8.63±2.67%），而2例正常镁血症型GS患者的TRPM6阳性区域占比接近正常水平（7.82±5.23%）。正常镁血症组患者的细胞内突变占比显著高于低镁血症组（92.31% vs 56.52%，p=0.02）。结论：正常镁血症在GS中并非罕见。血清镁浓度或可反映吉特曼综合征的疾病严重程度。