Tehran University of Medical Sciences Case Reports in Clinical Practice 2538-2683 6 1 2021 05 15 20 24 Nasim Khajavirad Department of Internal Medicine, School of Medicine, Tehran University of Medical Sciences, Tehran, Iran. Saeed Shakiba Department of Internal Medicine, School of Medicine, Tehran University of Medical Sciences, Tehran, Iran. Mahsa Abbaszadeh Department of Internal Medicine, School of Medicine, Tehran University of Medical Sciences, Tehran, Iran. Sahar Karimpour Reyhan Department of Internal Medicine, School of Medicine, Tehran University of Medical Sciences, Tehran, Iran. 2020 04 21 2020 08 04 Gitelman Syndrome (GS), also known as familial hypokalemia-hypomagnesemia, is a rare genetic disorder. GS presents with a specific defect in kidney function, that leads to hypokalemia, hypomagnesemia, metabolic alkalosis, and hypocalciuria. Here, we present a 30-year-old woman without a medical history. She experienced an episode of tonic-clonic seizure, generalized muscle weakness, and severe hyponatremia as the first presentation of GS. The interesting point of this case was her late-onset presentation and the long period of her disease diagnosis; thus, it highlights the importance of considering this diagnosis. https://crcp.tums.ac.ir/index.php/crcp/article/view/352 https://crcp.tums.ac.ir/index.php/crcp/article/download/352/392