Have you ever seen a lobster with an eroded looking shell, with lesions or spots on its back? Lobsters have been known to get shell disease, an epizootic disease caused by bacteria that could be affected by their environment. Between 1998 and 2004, shell disease has been observed in lobsters all the way up to mid-coast Maine. Shell disease is more prevalent in southern waters and corresponds to warmer water changes. (Journal of Crustacean Biology, n.d.)
Shell disease can cause mortality in lobsters which can attribute major economic losses and has not been known to be a threat to humans as it has not been linked to pollution.
Mutations can vary in lobsters in severity and type. When you see a blue, yellow, red, or even white lobster, that is a genetic mutation causing their color to be abnormal. Some lobsters have been documented with numerous claws on one arm, malformed claws, and even dual sex organs. Although lobsters with mutations like these are safe to consume, they are rare wonders and are often given to aquariums for preservation.