Abstract: The patient encountered by us had onset symptoms of intermittent limb weakness，accompanied by cough，sputum，and intermittent fever.His laboratory test revealed hypokalemia，hypomagnesemia and low urinary calcium，RASS system activity increased，with severe hyponatremia，lung infection at the same time，he was clinically diagnosed with Gitelman syndrome with SIADH.After being treated by anti-infection，water restriction，sodium and potassium supplementation，his weakness and electrolyte levels except for hypomagnesemia were improved significantly.SLC12A3 gene was detected with D486N monoheterozygous mutation，which confirmed the clinical diagnosis.This case suggests that when severe hypokalemia with hyponatremia occurs，the causes should be actively sought for identification and treatment.To avoid a delayed diagnosis，enough attentions should be paid to considering a variety of causes for diseases that can not be explained by only one factor clinically.

Key words: Gitelman syndrome, Hyponatremia, Inappropriate ADH syndrome, Genetic mutations

摘要： 本文报道了1例以间断四肢乏力起病，伴有咳嗽、咳痰、间断发热的患者，经检查发现低血钾、低血镁、低血氯、低尿钙及肾素-血管紧张素-醛固酮系统（RASS）活性增高，同时合并严重低钠血症、肺部感染，临床诊断为Gitelman综合征合并血管升压素分泌不当综合征（SIADH），经抗感染、限水、补钠及补钾治疗后，患者全身无力症状明显改善，除血镁变化不明显外，其余电解质水平得到显著改善。后期SLC12A3基因检测发现患者为D486N单杂合突变，再次验证了临床诊断。本病例提示当出现严重低钾合并低钠血症，应积极寻找原因鉴别施治。临床工作中发现疾病不能单从一元论解释时，需要从多种病因考虑，避免延误病情。

关键词: Gitelman综合征, 低钠血症, ADH分泌不当综合征, 基因突变