A frequent disease around these parts called "Hone Mange" very similar to normal
mange but seems to only effect one side of the body, normally outbreaks occur on the forearm first, then the disease moves to the calf of the leg, once to has eliminated the hair on the arm... Al;though no mites have been found that cause this form of the disease, there is a theory that they might be living in the scales of straight razors
Often the outbreak subsides or at least diminishes greatly after a year or so...