An elderly woman has been diagnosed with a rare brain disorder, state health officials said Monday.

There are about 300 U.S. cases each year of Creutzfeldt-Jakob disease, a fast-progressing illness that usually affects older people and leads to dementia, movement disorders and ultimately death.

In very rare cases, a form of the disorder can be caused by consuming meat products from cows infected with mad cow disease. However, Dr. Albert DeMaria, the state's director of communicable disease control, said that is unlikely in this case, given the woman's age and travel history. The women, in her 70s, is at a Cape Cod hospital.

There have been only three cases of the human form of mad cow disease in the entire United States, and each patient was believed to be infected outside the country.