D2I2.
genetic

Usher syndrome

Usher , also known as Hallgren syndrome, Usher–Hallgren syndrome, retinitis pigmentosa–dysacusis syndrome or dystrophia retinae dysacusis syndrome, is a rare disorder caused by a in any one of at least 11 genes resulting in a combination of hearing loss and visual impairment. It is the most common cause of deafblindness and is at present incurable.

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Plain-language summary adapted from Wikipedia. Not medical advice.