Early-onset Alzheimer's has stalked a poor extended family in Medellin, Colombia. The family carries a dominant gene that means that half are at risk. The disease strikes family members as young as 25 and by their 40s sufferers are in the grip of full-blown dementia. Alzheimer's is by and large a disease of the developed world, if for no other reason than that people in the developing world don't live long enough to suffer from it. Now by using the Colombian family to trial new drugs, researchers say they may be on the road to a global cure for Alzheimer's. Bill Law asks if this represents an unfair exploitation of desperate people - many of them barely literate - to benefit those in the West? Or is it a case of bringing hope to those in a hopeless situation?

Producer: Natalie Morton.