Most commonly LS appears in women on the genital skin. Typically, it presents in a reverse keyhole shape around the inner vulva and anus. The skin can also have just patches of white or less commonly the appearance of the skin can be reddened. LS is most common in women over the age of 50 though it can occur in younger women and children too. The incidence for children is 1 in 10,000.
Men can also get LS though it is a lot less common.
There are many theories out there ranging from LS being an autoimmune disorder to yeast overgrowth, bacteria, hormonal imbalance, and even one theory relating it to the Hepatitis C virus. At this point all of these ideas are just theories and there is no hard evidence for any of them. Sufferers often lean towards suspecting one or other based on their own situations and experiences. There may also be a genetic link. The most common would probably be fusing of the inner labia, narrowing of the vagina, and narrowing of the anus.