Hyponatremia is the most common electrolyte abnormality in children and underlying causes are many. It is most often caused by excessive salt loss from the gut but is also associated with severe systemic disorders in which there is actual or apparent aldosterone deficiency, such as congenital adrenal hyperplasia (CAH), which is the most common inherited disorder of aldosterone synthesis, and pseudohypoaldosteronism (PHA). Abscent aldosterone activity also leads to hyperkalemia which is characteristic for PHA and can result in life threatening arrythmias. This is a case report about a boy presenting with life threatening electrolyte disturbances in conjunction with PHA resulting from pyelonephritis and vesicoureteral reflux.