JEFFREY BROWN: And finally tonight, a medical mystery of our own time, where the search for a cure for Alzheimer's disease has taken researchers to a remote region in Colombia.
Tom Clarke of Independent Television News has the story.
A warning: Some of the medical footage is a bit on the graphic side.
TOM CLARKE: Antioquia, Colombia's isolated northern highlands.
I'm with Lucia Madrigal (ph), a nurse on her rounds from the regional medical school. Until recently, many of Lucia's patients were only accessible by horse or on foot. Once, she was detained for a week by drug traffickers, who still control much of this area. Now the roads have opened up, Lucia is closer to her patients, a group who lived for centuries in the shadow of a dreadful illness more prevalent here than anyone else on Earth.
Ophelia (ph) has Alzheimer's. She's only 51, but the disease has already taken her memories. Now she's losing the things she learned as a child, how to talk, how to write her name. Her symptoms are the same as for millions of Alzheimer's sufferers around the world. But Ophelia's disease is very different. She was always going to get it. She carries a mutated gene passed down from her mother, a cruel inheritance of early onset Alzheimer's that's been in the family for generations.
Since their mother died, her older sister Aura (ph) has run this household. She tells me that, of 16 brothers and sisters, eight inherited the disease. Four have died so far. Ophelia and her brother Gustavo (ph) now need full-time care.
WOMAN (through translator): Well, for me, it's very hard, because you think, for who is it more difficult, for oneself or the sick ones? Maybe we can say that they don't feel anything. But the truth is you don't know what they feel.
TOM CLARKE: In and around their town of Don Matias, they are not the only family suffering. As many as 5,000 people in Antioquia carry the mutation. Each of their children stand a 50 percent chance of inheriting the gene. Usually the disease strikes at just 49 years of age.
Here, the elderly watch the young die of Alzheimer's. It's thought a single Basque settler brought the disease here in the 18th century. His direct descendants carry what's called the Paisa mutation, a nickname given to Colombians from these hills.
The remoteness of these northern Colombian towns and villages is the reason the Paisa mutation has survived, passed on from generation to generation of the large families with little contact with the outside. But after nearly 300 years of isolated suffering, these families' plight has come to attention of the wider world because the mutation they carry could hold the key to preventing Alzheimer's in millions of sufferers around the world.
Francisco Lopera is the Colombian neurologist who discovered the mutation. For 25 years, he's worked to gain the trust and support of families. Now he and they are at the center of a major international scientific campaign.
DR. FRANCISCO LOPERA, University of Antioquia (through translator): Here, we have the severe problem of having the world's largest group of people with inherited Alzheimer's. The people are engaged with it, and families know that if they get involved in disease research here, they are contributing globally. They not only do it in order to find a solution for their problem, but also to help others.
TOM CLARKE: We traveled with Dr. Lopera back to Don Matias. With him is the man who coordinates Alzheimer's research at Harvard University. Adrian Ivinson has come to watch his colleague's routine evaluation of Ophelia and Gustavo, but also assess the potential these families have for a radically new approach to curing Alzheimer's.
ADRIAN IVINSON, Harvard University: Do you notice a difference in her?
DR. FRANCISCO LOPERA: Now, last time, she was talking better. Now she has lost many lines.
TOM CLARKE: They're the center of attention because efforts to treat Alzheimer's worldwide are failing. There is no predictive test for the common form of the disease, so drugs are only given once symptoms are apparent. By then, damage to the brain may be irreversible.
But here in Colombia, a simple genetic test reveals exactly which family members will develop the disease, decades before it strikes.
ADRIAN IVINSON: This gives us an incredible window of opportunity to look at the very earliest stages of this disorder. That gives us the opportunity to do two things. First of all, it gives us an opportunity to look at the disease process well before it's so bad that it causes symptoms. It also gives us the opportunity to try any future medications, any future drugs in a person whose brain is not so badly damaged.
TOM CLARKE: And back in the regional capital, Medellin, Dr. Lopera and his university colleagues are already on the case. They're not testing a new drug, but an existing one. With the support of two other U.S. institutions, they have recruited 300 family members in the first clinical trial aimed at preventing Alzheimer's.
Participants have given a blood sample and been tested for the mutation, but like all the families being studied, they have agreed not to know the results. As early as next year, researchers will try using an existing Alzheimer's drug and assess whether, given much earlier, it can successfully prevent or delay the disease.
DR. FRANCISCO LOPERA (through translator): It is probable that five years is too early for us to expect a cure for the disease, but that is the hope that we have.
TOM CLARKE: One thing that raises that hope, say other Alzheimer's experts, is the relationship here between the scientists and their research subjects.
And these cabinets hold the most striking demonstration of that alliance. Within are stored more than 50 brains donated by families whose loved ones died because of the mutation. It's the world's largest collection of brains from people with inherited Alzheimer's.
It may be unsettling, but a brain bank, as it's known, is essential in providing clues about how Alzheimer's begins to destroy the brain and how future drugs might work to stop it. But outside the lab, back in the homes of families like Ophelia, the specter of inherited Alzheimer's remains as terrifying as it always has been. And science can't move quick enough to allay the fears of those who may already carry the mutation.
WOMAN (through translator): What are the chances that, in the future, or how long will it be before we have cure?
ADRIAN IVINSON: This is the question I'm asked most, more than any other question. And I would like to be able to tell you how long it will take, but we can't.
TOM CLARKE: In all likelihood, a cure is still a long way off. But the contribution these families have already made could lead to new advances in Alzheimer's. Anything that delays the progression of the disease, even for just a few years, will help future generations here, as well the one in 10 of us that will develop Alzheimer's when we get old.