Pseudo-Bartter syndrome in an infant without obvious underlying conditions: A case report.

Pseudo-Bartter syndrome (PBS) develops owing to renal or extrarenal chloride loss, leading to hypokalemic alkalosis. Whereas most adult cases result from diuretic/laxative abuse, many infantile cases occur secondary to cystic fibrosis. Rarely, infantile PBS is caused by renal salt loss with anomalies of the kidney/urinary tract or genetic disorders, such as Dent disease. Here, we report the case of a 10-mo-old girl with a one-month history of decreased formula intake and 5.6% body weight loss. She showed typical laboratory findings as PBS, including hypokalemia (2.7 mEq/L) and high levels of bicarbonate (32.7 mEq/L) with a plasma renin activity of 399 ng/mL/h. With minimum supplementation of potassium and sodium, an improvement in body mass index, from -1.13 SD to +0.52 SD, with complete resolution of laboratory data was obtained in approximately one month. No causative mutations were identified in candidate genes for Bartter-Gitelman syndrome. Due to profound hypochloruria (< 15 mEq/L), PBS of renal origin was unlikely. In addition, extrarenal chloride loss did not seem to be the case, because the patient never manifested gastrointestinal symptoms. Therefore, we speculate that a temporary decrease in chloride intake, coupled with the putative genetic/epigenetic disadvantage of chloride retention, such as a subtle renal leak, may be responsible for the PBS in our patient.