[Polyuria and polydipsia in a 5 year-old child: diagnostic problems]

Polyuria and polydipsia could be present in three groups of diseases; polydipsia psicogena characterized by an excessive water intake, central diabetes insipidus (CDI) with a defect in the production of AVP and nephrogenic diabetes insipidus in which a defect in the renal response to vasopressin is present. In particular, CDI can be caused by lesions like germinoma and craniopharyngioma, Langerhans'cell histiocytosis, inflammatory, autoimmune and vascular diseases, trauma resulting from surgery or an accident; and in rare cases, genetic defects in the synthesis of vasopressin that are inherited as autosomal dominant or X-linked recessive traits. However, 30% to 50% of cases are considered idiopathic. Nevertheless, 30-50% of cases is considered idiopathic. Here we present the case of a 5.5 year-old female patient, referred to our Department of Endocrinology Surgery for polyuria and polydipsia. Hormonal tests demonstrated the presence of CDI with normal anterior pituitary function. Magnetic resonance imaging showed the lack of hyperintensity of posterior pituitary. Pituitary stalk was median and of regular volume. Diagnosis of CDI has been confirmed and therapy has been started with desmopressin (Minirin) 0.2 mg/die. During the follow-up the patient was in good conditions, presented an adequate hydro-electrolytic balance and normal growth velocity. Anterior pituitary function was normal and MR remained stable. This case report highlights problems concerning differential diagnosis and the importance of a careful follow-up which must involve the whole family.