Hiponatremia and hyperkalemia in a newborn can be a life threatening disorder caused by different diseases, including congenital adrenal hyperplasia, or less frequently by a genetical or acquired tubular cell resistance to aldosteron, called pseudohypoaldosteronism. Secondary pseudohypoaldosteronism is a rare, reversible electrolyte disorder caused by aldosterone resistance in infants with congenital urinary tract malformations and/or urinary tract infection.We present a 4-week-old boy with

more »

... re hyponatremia, hyperkalemia and elevated aldosterone levels during an episode of pyelonephritis. The disorder improved completely with antibiotic treatment, rehydration and electrolyte correction. Further investigations showed no structural urinary tract anomalies. According to the literature, we concluded that electrolyte disturbances were caused by aldosterone resistance of the inflamed tubular cells and subsequent defective transepithelial sodium transport.