The exact, underlying cause of idiopathic juxtafoveal retinal telangiectasia (IJT) is not known. IJT has been reported in some siblings (including twins) and other family members of affected people. This suggests there may be a genetic component to IJT; however, no specific gene has been proven to cause the condition. Researchers have considered that changes in the ATM gene may interact with other genes or environmental factors to predispose a person to developing IJT.
Some researchers have speculated that diabetes, or pre-diabetes, may be associated with some cases of IJT.  However, to our knowledge, this association has not been proven. Others have suggested there may be a developmental cause, such as abnormal formation of vessels in the eye, which could cause abnormalities of the vessels in adulthood.