There are over 70 known causes of deafblindness. Causes can be categorized into two groups: acquired and congenital.
Acquired
The majority of people with sight and hearing impairments have had both sight and hearing throughout most of their lives, and experienced a loss of those senses through illness, injury or age. Most people with acquired sight and hearing loss retain some useful sight and/or hearing. Some people have congenital deafness and acquired blindness (such as glaucoma or cataracts) or vice-versa.
Congenital
Children born deaf and blind are described as having congenital deafblindness. This condition may be due to prenatal infection (such as rubella), genetic/chromosomal syndromes (such as Down syndrome), birth trauma or maternal heavy drug and alcohol use. Some congenital conditions will not cause deafblindness until later in life. Maternal rubella was once the major cause of deafness and deafblindness in the west, but is now rare due to widespread vaccination programs.
Usher syndrome is also a major contributor to deafblindness. It is a genetic condition of people born deaf or hard of hearing, who gradually start to lose their sight. The sight loss usually begins in late childhood and is caused by an eye condition known as Retinitis Pigmentosa. Early symptoms include night blindness and loss of peripheral vision.