FAMILIAL HYPOKALAEMIA AND HYPOMAGNESAEMIA, GITELMAN'S SYNDROME, REPORT OF 6 CASES

Abstract

Six cases of renal wasting of potassium and magnesium are described in four families. Four patients presented with tetany, whilst two were asymptomatic siblings of these. One patient also suffered from a progressive external ophthalmoplegia syndrome and mental retardation, whilst the remaining five were normal in physical and intellectual development. One patient (now aged 31 years) has subsequently given birth to two normal children, but maintains very low serum levels of both potassium (2.0 mM) and magnesium (0.5 mM) when off electrolyte therapy. No abnormalities in calcium metabolism were found and there was no other evidence of tubular reabsorptive defect apart from slight defects in urinary concentration and acidification. In particular sodium chloride conservation appeared normal. Plasma renin levels were normal, or slightly raised in these patients and urinary aldosterone levels were normal, distinguishing this condition from Bartter's syndrome. Magnesium loading did not affect potassium wasting, nor did potassium loading alter the renal handling of magnesium. Spironolactone was able to improve tubular reabsorption of potassium, but not of magnesium. Treatment consists of magnesium and potassium supplements to the diet. Despite continuing severe renal losses of both potassium and magnesium these patients show very few or no overt symptoms over many years, and renal function is otherwise well preserved. It is suggested that this condition be known as Gitelman's Syndrome.