My thumb is  twitching  involuntarily , i'm  healthy  young and fit , i've got a regular notorious diet .But my thumb keeps twitching and i keep thinking it's because of Parkinson's decease , coz my grandmother's got it (as i could inherit it ) , but the symptoms of Parkinson's only start at the age of at least 40 (i'm not that old ! ) ...... please comment on my little para , give your suggestions 
Thankyou :)