Usher Syndrome, Type IC (USH1C)
Usher syndrome type 1C is an autosomal recessive disease caused by pathogenic variants in the gene USH1C. While it is a pan-ethnic disease, due to the presence of a founder mutation it is found more frequently in people of Acadian ancestry. The disease is characterized by congenital bilateral sensorineural deafness, which may be treated by cochlear implants; hearing aids do not help. Progressive loss of vision due to retinitis pigmentosa begins in childhood. Retinitis pigmentosa first presents with night blindness, but progresses to tunnel vision and eventually blindness. Patients also have problems with their balance and therefore experience developmental delay. Some patients with missense variants, rather than null variants, may manifest only with deafness; however, it is not currently possible to predict a patients phenotype based on genotype. Life expectancy is not reduced.
For information about carrier frequency and residual risk, please see the residual risk table.