Usher syndrome

Usher syndrome is inherited in an autosomal recessive manner.^[1] This means that a person must have a disease-causing change (mutation) in both copies of the gene associated with the syndrome in each cell to have Usher syndrome. One mutated copy is typically inherited from each parent, who are each referred to as a carrier. Carriers of an autosomal recessive condition usually do not have any signs or symptoms.

When two carriers of an autosomal recessive condition have children, each child has a 25% (1 in 4) chance to have the condition, a 50% (1 in 2) chance to be an unaffected carrier like each parent, and a 25% chance to not be a carrier AND not be affected.

Usher syndrome is an inherited disorder with different subtypes caused by mutations in any of a number of genes:^{[2][3][4][5][6]} 

Type I is divided in the following subtypes:

• IB, caused by mutations in the MYO7A gene (the most common one)
• IC, caused by mutations in the USH1C gene
• ID, caused by mutations in the CDH23 gene
• ID-F, caused by mutations in the PCDH15 and CDH23 genes
• IF, caused by mutations in the PCDH15 gene
• IG, caused by mutations in the SANS gene
• IH, caused by mutations in the USH1H gene
• IJ, caused by mutations in the CIB2 gene 
• IK, caused by mutations in the USH1K gene

Type II is divided in the following subtypes:

• IIA, caused by mutations in the USH2A gene
• IIC, caused by mutations in the ADGRV1 gene
• IID, caused by mutations in the WHRN gene
• IIC, GPR98/PDZD7, caused by mutations in the ADGRV1 (ADGRV1 is also known as GPR98) and PDZD7 genes

Type III is divided in the following subtypes:

• IIIA, caused by mutations in the CLRN1 gene
• IIIB, caused by mutations in the HARS gene

Please see the list of the different types and subtypes of Usher syndrome and their specific gene mutations provided by OMIM.

Many of the genes related to Usher syndrome give instructions to make proteins needed for normal hearing, balance, and vision. The signs and symptoms of Usher syndrome occur when these genes have mutations that impair how they function. In some cases, the exact role of the genes involved is unknown. In some cases no mutation is identified, and it is believed that other genes may be involved.^[1]