RESUMEN
Classic salt-wasting 21-hydroxylase deficiency (21-OHD) often requires fludrocortisone (FC) replacement. However, the optimal dose of FC varies between patients and the dose needs to be adjusted depending on the degree of symptoms. Further, the aldosterone resistance due to urinary tract infections causes salt-wasting symptoms. We recently encountered a patient with 21-OHD who required up to 0.36 mg/day of FC in order to control hyperkalemia despite adequate hydrocortisone (HC) administration. This condition was presumed to be due to aldosterone resistance complications associated with urinary tract infections. Thus, if the initial treatment of 21-OHD with HC and FC is resistant, then one should consider complications that may cause aldosterone resistance, such as urinary tract infections.