We undertook genetic analysis of individuals with Usher syndrome; this is a genetic recessive disorder consisting of visual impairment leading to blindness, congenital deafness, and sometimes balance problems. We sequenced all the 9 genes known to cause Usher to date in all of the subjects, who were from a wide variety of ethnic backgrounds. We identified the molecular cause of Usher in 86% of the cohort; our results demonstrate that only one gene causes Usher in any individual and we found no robust evidence that in an individual, mutations in more than one gene cause the disorder (digenic inheritance). (By Dr Maria Bitner-Glindzicz, http://jmg.bmj.com/content/early/2011/11/30/jmedgenet-2011-100468.abstract?papetoc )