Fraud marriage.

I married 4 months ago.My wife hide her disease retina pigmentosa before marriage, this disease is genetic and incurable in which her vision loss progressively and also night blindness.her family members also hide her disease before marriage.After marriage i realized that she has something problem with her vision so I show her eye specialist then we knew she is suffering such incurable disease. doctor also suggests don't plan for child it may be this disease carry in your child, so I can't take such risk. my wife and her family fraud with me and they hide her incurable disease. so please help how can I take legal action?