Diabètes insipides néphrogéniques

Nephrogenic diabetes insipidus (NDI) which can be inherited or acquired, is characterized by an inhability to concentrate urine despite normal or elevated plasma concentrations of the antidiuretic hormone, arginine-vasopressine (AVP). Polyuria, with hyposthenuria and polydipsia are the cardinal clinical manifestations of the disease. Hypercalcemia, hypokaliemia, lithium administration and chronic renal failure are the principal causes of acquired NDI. About 90 percent of patients with congenital NDI are males with X-linked recessive NDI who have mutations in the arginine-vasopressin receptor 2 (AVPR2) gene that codes for the vasopressin V2 receptor. The gene is located in chromosome region Xq28. In less than 10 percent of the families studied, congenital NDI has an autosomal recessive or autosomal dominant mode of inheritance. In these cases, mutations have been identified in the aquaporin-2 gene (AQP2), which is located in chromosome region 12q13 and codes for the vasopressin-sensitive water channel. Other inherited disorders with mild, moderate or severe inhability to concentrate urine include Bartter’s syndrome and cystinosis. Identification of the molecular defect underlying congenital NDI is of immediate clinical significance because early diagnosis and treatment of affected infants can avert the physical and mental retardation associated with episodes of dehydration.