Usher syndrome

Usher syndrome, also known as Hallgren syndrome or retinitis pigmentosa-dysacusis syndrome, is a rare genetic disorder caused by a mutation in any one of at least eleven genes, producing a combination of progressive hearing loss and vision loss, and is inherited in an autosomal recessive pattern requiring both parents to carry the mutated gene. The vision loss results from retinitis pigmentosa, a breakdown of the retina that first causes night blindness and then a gradual narrowing of peripheral vision, while the hearing loss comes from damage to the hair cells of the cochlea that normally carry electrical signals to the brain. It is the most common inherited cause of combined deafness and blindness and currently has no cure. The condition is grouped into three main types that differ in severity and onset: type one causes profound deafness from birth along with early vision loss and balance problems, type two produces partial hearing loss from birth with vision loss beginning later, and type three involves progressive hearing loss after birth together with variable, later-onset vision and balance problems.