If you haven't heard of Rett syndrome, it's probably because it's very rare. Affecting an estimated one in 12,000 baby girls born each year (and only rarely seen in boys), this genetic disorder causes problems in brain development. And while it may be very rare, Rett syndrome causes severe mental and physical disability in its sufferers. Life for those living with Rett syndrome, and for those caring for someone with the condition, can be very difficult.
Intrigued? Then check out this gallery to learn all about Rett syndrome.