We report a 2 month-old infant referred for failure to thrive. At birth, weight was 3820 g and length 52 cm. After physiologic weight loss, the patient showed no further weight gain for the next two months. On admittance (age 2 mo), weight was 3340 g and length 53 cm; the infant had severe dystrophy, generalized hypotonia and dehydration; blood chemistry showed hyponatremia, hyperkalemia and hypochloremia. A salt losing syndrome of adrenal origin was hypothesized. However, rehydration and hydrocortisone administration failed to correct hyponatremia and hyperkalemia. Endocrine assessment showed high levels of aldosterone and plasma renin activity, suggesting pseudohypoaldosteronism. Oral sodium chloride supplementation normalized electrolyte balance and the patient showed progressive weight gain and catch-up growth, confirming the diagnosis.