The article describes congenital aldosterone synthase deficiency (ASD), a subgroup of primary hypoaldosteronism caused by mutations in the CYP11B2 gene, characterized by hyponatremia, hyperkalemia, and elevated plasma renin with normal cortisol production. Two mutations in the CYP11B2 gene were detected in a male newborn born at 26 + 2 weeks of gestation by emergency caesarean section: novel c.457G > C (p.A153P) and c.1009C > T (p.Q337), which affect the structure and function of the protein. Laboratory tests revealed severe hyponatremia, hyperkalemia, elevated renin, low cortisol, and very low aldosterone confirmed by mass spectrometry. So far, 82 mutational sites in this gene have been reported, including c.457G > C. The patient was treated with 9α-fluorohydrocortisone, biochemical parameters and renin normalized after 1 month, and cortisol after 3 months. The study confirms the first identification of the p.A153P mutation associated with the classical phenotype of hypoaldosteronism and expands the mutational spectrum of CYP11B2. Persistent hyponatremia requires genetic testing for early diagnosis and long-term follow-up to optimize treatment.[1]