Bartter syndrome is a rare heterogeneous disease characterised by a deficiency 
in sodium and chloride absorption. Gain-of-function mutations in the CASR gene 
have been described in some patients with Bartter syndrome associated with 
hypocalcaemia and hypercalciuria. We describe a case of adult-onset Bartter 
syndrome with hypocalcaemia severe enough to cause osteomalacia.
LEARNING POINTS: Bartter syndrome is one of the rare heterogenous diseases that 
present with electrolyte disturbances.Bartter syndrome type 5 also causes 
hypercalciuria which is not severe enough to cause osteomalacia.Patients with 
adult-onset Bartter syndrome should be screened promptly for osteomalacia to 
prevent pathological fractures and consequent complications.