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The various causes are carpel tunnel syndrome, inflammation of the tendon of the hand due to repetitive work, gout, lymphangitis, deep vein thrombosis, osteoarthritis and rheumatoid arthritis. You need to consult a doctor and rule these out by blood tests, X-rays, nerve conduction studies, rheumatoid factor, ESR, etc.
Since the thumb twitches uncontrollably, symptoms could be due to carpal tunnel syndrome. In this the median nerve is compressed at the wrist in a place called the carpel tunnel. Symptoms begin with numbness and tingling of the first three or two fingers from the thumb side (twitch is also possible). Nerve conduction studies are quite diagnostic. Treatment is usually by splints and steroid injections. Surgery may be required in some cases. This condition is common in those who use the key board, mouse etc a lot—like in computers or in typing jobs.
Please consult your PCP for primary examination followed by proper referral.
sounds like athritise i have the same problem