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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.