OPTN and bone Paget disease: Optn has been linked to different pathologies since mutations in the Optn gene have been associated with different primary and juvenile forms of Open-Angle Glaucoma (the most frequent mutation being E50K) as well as with Amyotrophic Lateral Sclerosis (ALS) and polymorphisms of Optn gene are risk factor for Paget’s disease of bone [32].