Diabetes insipidus can be subclassified into two broad categories depending on whether the disorder is secondary to decreased synthesis and secretion of AVP (Central DI – CDI), or to insensitivity of the renal distal tubules and collecting ducts to AVP leading to a decreased insertion of AQP2 channels into the apical cell membrane of the renal principal cells and a subsequent decrease in AQP2–mediated free water reabsorption (Nephrogenic DI – NDI) (3). The gene discussed is AQP2; the disease is Central diabetes insipidus.