A new tubular disorder with hypokalaemic metabolic alkalosis, severe hypermagnesuric hypomagnesaemia, hypercalciuria and cardiomyopathy

1Stem cell and Transplantation Services, Finnish Red Cross Blood Service and 2Division of Nephrology and Transplantation, Hospital for Children and Adolescents, University of Helsinki, Helsinki, Finland Renal tubular magnesium loss in association with a defect in tubular chloride reabsorption has been reported in Bartter's and Gitelman's syndromes. Clinically, both syndromes are characterized by hypokalaemic metabolic alkalosis, renal salt wasting, hyperreninaemic hyperaldosteronism and altered renal prostaglandin metabolism [1]. In Bartter's syndrome, hypomagnesaemia occurs in ∼20% of patients, but is usually mild. Hypercalciuria may also occur. In Gitelman's syndrome, hypomagnesaemia due to renal loss is the cardinal finding. However, hypocalciuria is pathognomonic for this syndrome and used in the differential diagnosis between the two disorders. Both syndromes are considered to be autosomally recessively inherited. We report a novel Bartter-like phenotype in a father–daughter pair. This seemingly autosomally dominantly inherited disease is characterized by hypokalaemic metabolic alkalosis secondary to renal chloride loss and severe hypomagnesaemia due to renal magnesium loss. In contrast to Gitelman's syndrome, these patients showed marked hypercalciuria. Both patients developed dilating cardiomyopathy, which was fatal in the father and required heart transplantation in the daughter.