This sounds like it is probably acanthosis nigricans. According to my endocrinologist it occurs mostly in areas where there is pressure or friction. I'm not sure what would cause it on your knuckles, but elbows are apparently common, especially if you lean on them. Knees too. She has treated Muslim patients who have a patch on their forehead where it touches the mat when they pray.
She seems to think that mine (mostly underarms) will go away eventually when the IR is under control. |