Maybe you have lead poisoning?
"The subjects of lead-poisoning often suffer from gout when they have reached middle or later life...'saturnine gout' is invariably in those whose parents were gouty, and so frequent that most sufferers from chronic lead-poisoning are distinctly gouty." *
"A characteristic symptom is a narrow, bluish-black line on the gums, close to the teeth, distinguished by its narrowness and tint from the more common zone of purplish congestion." *
*taken from 'A manual of diseases of the nervous system' by W.R. gowers, (1893)