Patients with Usher syndrome typically have progressive visual impairment due to retinitis pigmentosa (RP) and varying levels of deafness with or without vestibular involvement. Usher syndrome type 2 is the most common of the 3 clinical subtypes that have been described; it is associated with RP, moderate to severe congenital hearing impairment, and normal vestibular function. Autosomal recessive mutations in USH2A are the most common cause of Usher syndrome type 2.1 Although a high degree of clinical heterogeneity has been described in USH2A-related disease, the ocular phenotype is usually concordant within families. Herein, we describe 2 siblings harboring the same USH2A mutations (c.[1036A>C];[13316C>T], p.[Asn346His];[Thr4439Ile]) with very different ocular and electrophysiological phenotypes.
Lenassi E, Robson AG, Luxon LM, Bitner-Glindzicz M, Webster AR. Clinical Heterogeneity in a Family With Mutations in USH2A. JAMA Ophthalmol. 2015;133(3):352-355. doi:10.1001/jamaophthalmol.2014.5163