Dermatophagia - extreme nail biting / biting of skin to point of an obsessive compulsive disorder (OCD) or other condition leading to self mutilating behaviour such as autistic spectrum disorders (as is the case in this example) or Lesch-Nyhan Syndrome.
<a href="//commons.wikimedia.org/wiki/User:6th_Happiness" title="User:6th Happiness">6th Happiness</a>
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