Encyclopedia of Feline Veterinary Medical Information
Baldness
Cats have a pattern baldness (like human baldness) in which there is hairloss at the base of the ears. This usually occurs in an oval pattern between the base of the ear which extends out close to the eye. Usually this type of baldness is not associated with hairloss anywhere else on the body, to the best of my knowledge.
Please see http://www.vetinfo.com/catfur.html for more reasons for hairloss in cats.