Usher syndrome: Genetic diagnosis and current therapeutic approaches

Table 1 Comparison between Usher syndrome types and symptoms

Type	Hearing loss	Vision loss	Vestibular function
Type 1	Profound bilateral hearing loss at birth[26,149]	Earlier onset, in the first decade of life[13,26]	Vestibular areflexia at birth[26]
Type 2	Moderate to severe hearing loss at birth[13,24]	Late childhood or teens[26]	Normal[44]
Type 3	Normal at birth, with progressive loss[28,164]	Commonly in early youth[13,26]	Variable[38]

Table 2 Comparison between Usher syndrome genes, OMIM number, representative mutations, and ethnic/geographic regions

Genes	OMIM number	Representative mutations	Ethnic/geographic regions
MYO7A	276903[47]	Deafness, autosomal dominant 11; Deafness, autosomal recessive 2; Usher syndrome, type 1B[47]	China, Japan, Pakistan, Netherlands, Iran, and Sweden[47]
USH1C	605242[48]	Deafness, autosomal recessive 18A; Usher syndrome, type 1C[48]	Louisiana Acadians, and Lebanon[48]
CDH23	605516[49]	Deafness, autosomal recessive 12; Usher syndrome, type 1D[49]	Cuba, Germany, and Japan[49]
PCDH15	605514[50]	Deafness, autosomal recessive 23; Usher syndrome, type 1F[50]	Pakistan[50]
USH1G(SANS)	607696[51]	Usher syndrome, type 1G[51]	Tunisia, Germany, and Jordan[51]
USH2A	608400[52]	Retinitis pigmentosa 39; Usher syndrome, type 2A[52]	Denmark, Norway, Spain, and Iraqi Jewish[52]
ADGRV1	602851[53]	Usher syndrome, type 2C; Usher syndrome, type 2C, GPR98/PDZD7 digenic; Familial Febrile Seizures 4[53]	Japan and France[53]
WHRN	607928[54]	Deafness, autosomal recessive 31; Usher syndrome, type 2D[54]	Palestine, Tunisia, and Germany[54]
CLRN1	606397[55]	Retinitis pigmentosa 61; Usher syndrome, type 3A[55]	Italy, Ashkenazi Jewish population, and Spain[55]
ABHD121	613599[56]	Polyneuropathy, hearing loss, ataxia, retinitis pigmentosa, and cataract[56]	Norway, United Arab Emirates, United States, Algeria, Spain, and Netherlands[56]
HARS1	142810[57]	Charcot-Marie-Tooth disease, axonal, type 2W; Usher syndrome type 3B[57]	Old Order Amish families in Pennsylvania[57]

¹In study phase.