Skin on his hand is now cold and hard to the touch What could be wrong?

There are several possible causes for cold and hard skin on the hand, including:

- Raynaud's syndrome: This is a condition that affects blood flow to the fingers and toes. It can cause the skin to become cold, numb, and pale or blue.

- Frostbite: This occurs when the skin is exposed to extreme cold for too long. It can cause the skin to become cold, hard, and numb.

- Scleroderma: This is a rare autoimmune disease that can cause the skin to become thick, hard, and tight.

- Dermatomyositis: This is a rare autoimmune disease that can cause the skin to become weak, inflamed, and scaly.

- Calcinosis cutis: This is a condition that causes calcium deposits to form in the skin. It can cause the skin to become hard and lumpy.