House of the Scorpion by Nancy Farmer
Matt is six years old when he discovers that he is different from other children and other people. To most, Matt isn't considered a boy at all, but a beast, dirty and disgusting. But to El Patron, lord of a country called Opium, Matt is the guarantee of eternal life. El Patron loves Matt as he loves himself - for Matt is himself. They share the exact same DNA. As Matt struggles to understand his existence and what that existence truly means, he is threatened by a host of sinister and manipulating characters, from El Patron's power-hungry family to the brain-deadened eejits and mindless slaves that toil Opium's poppy fields. Surrounded by a dangerous army of bodyguards, escape is the only chance Matt has to survive. But even escape is no guarantee of freedom... because Matt is marked by his difference in ways that he doesn't even suspect.