A woman who was told by her doctor to rinse her sinuses twice daily to clear up a chronic sinus infection died from a brain-eating amoeba.

The woman, 69 from Seattle, was using tap water filtered using a Brita Water Purifier in a neti pot, according to a report published in the peer-reviewed International Journal of Infectious Diseases. The Centers for Disease Control and Prevention recommends that only distilled, sterile or cooled boiled water be used for sinus irrigation.

After a month of clearing her sinuses with the non-sterile water, a quarter-sized red rash appeared on the right side of her nose. Her doctor told her it was rosacea and prescribed an ointment, according to the report. The rash didn't clear and she saw a dermatologist several times seeking answers, but biopsies didn't result in any definitive diagnosis.

A year after the rash developed, the woman had a seizure. At that time, a CT scan showed a half-inch lesion on her brain. Doctors performed surgery to remove the mass, which they say had "unusual characteristics." A specimen was sent to Johns Hopkins University for analysis.

Days later, her left arm and leg became numb and she had an "altered mental status." A consulting neuropathologist from Johns Hopkins suggested there might be an amoebic infection and later a drug for such infection was given to the patient. However, her condition didn't improve and her family ultimately decided to take her off life support.

Tests after death showed the woman died of Balamuthia mandrillaris, an amoeba that lives in soil and the Centers for Disease Control and Prevention also say it's possible it lives in water. Balamuthia can travel to the brain and can cause a deadly infection. Little is known about how people contract the amoeba and how to prevent it.

She tested negative for Naegleria fowleri, another amoeba able to cause deadly brain infections that was linked to a death of a Louisiana man who used a neti pot in 2013.

More:Brain-eating amoeba found in Louisiana water system

More:Deadly brain-eating amoeba symptoms are difficult to identify

The Seattle article authors warn that because cases such as this one are so difficult to diagnose, "it is possible that many more cases of Balamuthia have been missed."

Around the world, more than 200 cases of Balamuthia infection have been diagnosed with at least 70 cases in the U.S., according to the CDC.

Follow Ashley May on Twitter: @AshleyMayTweets