Background: Bartter syndrome (BS) is a heterogeneous ion channel disorder characterized by hypokalemia, hypochloremia, metabolic alkalosis and hyperreninemia with normal blood pressure. Case report: We report a case of a boy who was referred to our clinic with a medical history suggestive of antenatal BS. The molecular analysis confirmed the clinical suspicion of BS (type I), although his potassium serum concentration was always in normal range (median 4.1 mmol/l, range 3.7 a€“ 4.7), requiring only a very low dose of indomethacin as treatment protocol. Over the follow-up period he presented myotonia of the limbs and bilateral equinism and was admitted for severe weakness and intense muscular cramps involving the lower extremities. Laboratory tests showed creatine kinase (CK) 27295 U/l, and normal serum potassium (4.3 mmol/l). A hypokalemic rhabdoyolysis could be excluded. The DNA analysis confirmed the hypothesis of Becker's Muscular Dystrophy (BMD). Conclusion: The coexistence of a muscular disorder can alter the biochemical features of BS by causing normal serum potassium concentration and normokalemic rhabdomyolisis. This unusual biochemical pattern of BS type I should be properly investigated to avoid mismanagement and prevent severe complications.