Ciliopathies are a group of disorders caused by a defect in ciliogenesis, 
ciliary protein trafficking. Because nearly every cell in the body (including 
the photoreceptors) contains cilia, defects in ciliary proteins typically affect 
multiple organ systems. Usher syndrome is the most common syndromic cause of 
retinitis pigmentosa (RP) and accounts for 10-20% of cases of RP Inheritance is 
autosomal recessive, and the retinal dystrophy is usually rod-cone dystrophy 
(Figs. 32.1 and 32.2). These patients have RP with sensorineural hearing loss 
(partial or complete) since birth; some may have vestibular dysfunction. Most 
patients retain central vision of about 20/40 until about age 40. Usher Syndrome 
1 (USH1): Profound congenital sensorineural hearing loss on audiometry, absent 
vestibular function, and typical RP (onset by 10 years of age); accounts for 
about 70% of all Usher cases. Patient may benefit from a cochlear implant. The 
retinitis pigmentosa occurs at an early age (childhood onset) and progress 
slowly. Usher Syndrome 2 (USH2): Moderate to severe congenital sensorineural 
hearing loss on audiometry (predominantly for higher frequencies), normal 
vestibular function, and typical RP (onset by 20 years of age); accounts for 
about 26% of all Usher cases. Usher Syndrome 3 (USH3): Progressive sensorineural 
hearing loss and typical RP (onset in second decade); accounts for about 4% of 
all Usher cases. Vestibular function is normal in about half of patients, but 
abnormal in the other half.