Patient with Bartter syndrome in whom chronic potassium depletion was considered one of the causes of hyponatremia.

A 53-year-old man was admitted to our hospital because of general fatigue and disorientation. He had been diagnosed with Bartter syndrome in his teens and had been taking potassium preparations since then. However, his serum potassium concentration (K+ s) remained persistently low. Ten days before admission, he developed fever. He was diagnosed as having bronchitis and was treated with antibiotics. Although his fever subsided, general fatigue worsened. Laboratory examination showed hyponatraemia (127 mEq/L), while K+ s was 2.3 mEq/L. C reactive protein was negative. On admission, laboratory examination revealed deterioration of hyponatraemia (125 mEq/L). Although his serum sodium concentration (Na+ s) was refractory to electrolyte replacement, the level increased towards normal after spironolactone administration, following normalisation of K+ s, suggesting that hyponatraemia was caused by K+ depletion. Physicians should be aware of the importance of the effects of exchangeable K+ (K+ e) on Na+ s.