Immunohistochemical and ultrastructural studies showed that the endolymphatic sac of MD patients had excessive secretion of glycoprotein (13, 14), and the overexpression of aquaporin-2 in the endolymphatic sac epithelium was also involved in the formation of endolymphatic hydrops (15), suggesting that the endolymphatic sac secretion exceeded absorption, increasing the inner ear pressure. This evidence concerns the gene AQP2 and Menkes disease.