Two likely cases of a mysterious, fatal brain disorder have been reported in McLennan County — a statistical anomaly considering that only one in 1 million people worldwide is affected by the condition in any given year.

Adding to the peculiarity is that the noncontagious disorder belongs to the same family as Creutzfeldt-Jakob disease.

One of its forms is believed to be triggered by people eating meat from cattle infected with mad cow disease.

As frightening as that might sound, officials said residents shouldn’t be alarmed.

One of the local cases definitely is not the type associated with mad cow disease, and there is no evidence the other one is, either. More importantly, the disorder cannot be transmitted from person to person, officials said.

“To have potentially two cases this close together is statistically unusual,” said Dr. Farley Verner, an infectious disease specialist who advises the Waco-McLennan County Public Health District. “But because of the type of disorder it is, and because of what we know about how it develops, it’s not a worrisome coincidence. It’s just a coincidence.”

Because of privacy laws, health officials can release only limited details about the local cases. Both were reported in May.

The first case involved a 49-year-old man from McGregor, Hammad Akram, the health district’s epidemiologist, said. The man has since died.

Initial results from an autopsy show he had some type of human prion disease, a family of diseases involving an abnormal protein.

Creutzfeldt-Jakob disease, or CJD, is the most common type of human prion disease. The autopsy ruled out CJD, however, Akram said.

The second case involves a Waco woman in her late 40s, Akram said. Her symptoms point to CJD, but since the only way to confirm the disease is to study brain tissue after death, that diagnosis is not confirmed, he said.

No apparent link

There is no apparent link between the two local victims, Akram said.

Prion disease usually occurs in people older than age 60.

Doctors give patients a “working diagnosis” of human prion disease based on certain symptoms, combined with results from a blood test, Farley said.

The symptoms are similar to those of other neurological conditions: confusion, difficulty remembering recent events, loss of feeling in certain body parts, balance problems, difficulty walking and muscle jerks and spasms.

If a physician rules out other causes for such symptoms, a blood test can be done that indicates whether the person has a genetic mutation associated with human prion disease. The test cannot confirm it, but positive results make the diagnosis more likely, Verner said.

The name of the disease category comes from a protein called a prion.

People have normal prions, which are concentrated in the brain. But in some instances, there is abnormal prion protein, which causes normal prions to be converted to abnormal form.

That destroys brain tissue and is eventually fatal. The process can take years, but most people die within three months to a year of having symptoms.

There are three main categories of human prion disease — sporadic, familial and acquired.

Sporadic cases start spontaneously, without a clearly identifiable cause. They account for about 85 percent of all human prion disease, according to the National Prion Disease Pathology Surveillance Center.

Familial cases are inherited and are caused by a defect in the prion protein gene, the center said.

Acquired cases are transmitted by infection, which can occur if a person receives a transplant infected with prion disease or undergoes surgery where contaminated instruments are used, according to the center.

Another avenue of infection is when someone eats contaminated beef, the center said. That’s where the connection to mad cow disease comes in.

Only three cases linked to contaminated beef have been found in the United States, according to health officials. In all three cases, the victims are thought to have been infected while living overseas.

In Texas, about 120 people died from human prion disease between 2000-08, according to state data.

Last year, there were 19 probable or confirmed cases of sporadic CJD and two familial CJD cases statewide.

McLennan County has not had any human prion disease cases in the past decade, according to state records. Verner said he can only recall two or three cases in the 25 years he has been here.

cculp@wacotrib.com

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