Does anyone know what kind of skin disorder that would turn your hands including the palm of your hands black.

Literally the color black. This has ocurred on a african american male. It started about 5 months ago and got worse. His dermatalogist don't know what it is but prescripted a cream for him to apply. The first cream didn't work and seem to make it worse. Then he Rx another cream and it seems to be helping but the doctor still doesn't know what it is or what caused it. My friend is 64 years old. Some parts of his fingers and palms has very hard callouses and the skin is very hard. Parts of his hands have begun to lighten up somewhat. Can someone help. I told him it may be time to seek another doctor.

I have no idea what this could be. Is there something he comes into contact with on a regular basis with his hands? Perhaps as a part of his job? The hard skin sounds like scleroderma but the hyperpigmentation (darkening) doesn't quite fit. Suggest to him again to see a different dermatologist and have a check up with his primary care provider to rule out disease or other disorders.