Hello, my Cornish Rex has had a wonderful coat since birth. A couple of month ago the hair began to fall out. We thought it was shedding, but up to now new hair hasn't grown again. The back and the area behind the ears is almost hairless. The chest and the shoulder blades are still covered with curls. She's neutered and we feed her Guabi Natural. Any ideas?
i can only think of genetic probs, a disease, and a lack of nutrients. i don't know if you can exclude the first two for sure but if yes perhaps you should reconsider her diet. search the forum for "holistic food" and you'll find some very useful posts ^_^
How old is she? When exactly did this start? does she lick the area a lot? how is her skin? do you bathe her regularly? if so what shampoo do you use? does she have problems of very oily\very dry skin? what are you feeding her? does she eat wet food?

this could be due to an eczema a rash or Miliary dermatitis which is a flea allergy, lack of vitamins can also cause this like lack of vitamin E, It could be Hypotrichosis which can be cause by bad breeding and can cause hair loss and complete baldness in cats (and other animals including humans), this can also be due to stress if something has recently changed (anything from changing food or litter to moving house to having a baby or a new pet!)
there is really a lot of things that can cause this
My cats have hair loss due to food allergies-especially red dye. My vet recommended z/d (i don't know if I'm allowed to say the brand. We do mix in a little other stuff so their lives are not boring, but too much and the male looks like he has been shaved straight down the back and top of tail. My female around the neck.