5epto-optic dysplasia is a rare inborn defect characterized by hypoplasia of the optic nerves, morphological abnormalities of the methan brain structures and impaired secretion of pituitary and possibly hypothalamic hormones. This inborn abnormality was found in a pacient with central diabetes insipidus and impaired perception of thirst. secretion of other hormones from the region of the hypothalamus and pituitary is normal. The boy has a bilateral hypoplasia of the optic nerves, absence of the septum pellucidum, corpus callosum, columnae fornicis and comissura anterior fornicis and a cyst in the area of the pineal gland. Isolated diabetes insipidus is an uncommon manifestation of septo-optic dysplasia. Impaired perception of thirst may be due to impaired development of methan brain structures in the hypothalamic region. In combination with diabetes insipidus it led to repeated severe upsets of the internal environment.

        Key words: septo-optic dysplasia, diabetes insipidus, impaired perception of thirst