<s>[INST] I have pain in the palm of my hand below the thumb. There is a vein that seems enlarged. It hurts to open a jar, button, press thumb back... I don t have any numbness. I had an X-ray a couple of months ago and there was no arthritis there. My internist suggested I see a hand specialist. What could it be. [/INST] Cannot say in your particular case without an examination but certainly carpal tunnel is quite common. This is an irritation of nerves near the wrist due to repeated use.Their can be many other causes first, carpal tunnel can occur from thyroid disease, previous injury, or other disorder. Also, previous trauma can cause irritation to other structures. There could in theory be problems in blood circulation, but this is extremely uncommon because arteries come into the hand from both sides, so it is hard to have a problem bad enough to be noticeable. Can be just a sore muscle or tendon. </s>