1. Immediately consult and retain professional assistance for this problem since it is causing tissue damage and you will need professional assistance to address this problem.
2. Try to observe what situations this occurs and what some of the "triggers" are for the behavior.
3. The cause of the behavior and consequences vary with each individual child and should be investigating with the assistance of a trained professional.
4. Try not to overact before designing a plan for treatment since the behavior may be maintained by attention or a reaction from the parents.
5. Try to take immediate safety precautions such as close monitoring of your child to try to prevent the behavior from occurring while designing a procedure to address the problem. This can be done by leaving doors open at night, security monitoring video cameras or just trying to be with your child as much as possible or have someone else with them to prevent the problem.
This is a problem not to be taken lightly and should be addressed immediately and with professional guidance.