dry black scaly skin

My dad has black scaly skin that started on his legs.  It is now going up his neck.  It is so dry you can just pick it off. It almost looks like it has been burned.  He has tried so many different lotions but nothing helps.  When he did see a doctor they took a patch off his back, he was told it was just dry skins.  This is bothering him.  He is 83yrs old, an african american man .  Please can you give us some kind of information on what this might be?