Common glaucoma is traced to gene changes
Researchers have identified two mutant forms of a single gene that are responsible for 99% of cases of a common form of glaucoma.
Glaucoma is a leading cause of blindness worldwide, second only to cataracts.
The gene mutations cause exfoliative glaucoma, in which a protein called elastin builds up in the ducts that drain excess fluid from the eye.
The undrained fluid puts pressure on the optic nerve, eventually leading to blindness.
Between 10% and 20% of people older than 60 have some symptoms of exfoliative glaucoma, and 60% of those develop the full-fledged form.
Researchers at Uppsala University in Sweden and deCODE Genetics Inc. and National University Hospital, both in Reykjavik, Iceland, studied genetic material from 16,000 people in the two countries.
They reported Friday in the journal Science that one mutation of the LOXL1 gene conferred 26 times the risk of exfoliative glaucoma, the other mutation eight times the risk.
People with two copies of the high-risk mutation were 100 times as likely to develop the disorder.
LOXL1 is the blueprint for an enzyme called lysyl oxidase-like protein 1, which cross-links elastin fibers and stabilizes them.
The defective genes produce slightly lower amounts of the protein, allowing elastin fragments to build up over long periods.
DeCODE said it would have a diagnostic test for the gene by the end of the year.
