Megalocornea (MGC1) is a rare congenital disease of the anterior eye segment characterized by bilateral enlarged corneas with a horizontal diameter of 13 mm or more (measured after the age of two years) and reduced central corneal thickness in the absence of raised intraocular pressure (IOP). It is an important differential diagnosis for primary congenital glaucoma (PCG) [DS:H01203] that leads to a high risk of vision loss and needs a fast diagnostic clarification and prompt treatment. Furthermore, MGC1 is classified as non-syndromic and has to be distinguished from megalocornea in the context of syndromes, e.g. neonatal Marfan syndrome [DS:H00653] or megalocornea-mental-retardation (MMR) syndrome. MGC1 has been reported to be caused by mutations in the CHRDL1 gene on Xq23.
