Osteomalacia in a Case of Adult-Onset Bartter Syndrome

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.