A more thorough explanation:

The thin-skull rule, also known as the eggshell-skull rule, is a principle in tort law that holds a defendant responsible for a plaintiff's unforeseeable and uncommon reactions to the defendant's negligent or intentional act.

For example, if someone negligently bumps into another person who happens to have a rare medical condition, such as hemophilia, and the person with hemophilia suffers severe injuries, the negligent defendant is liable for the full extent of the plaintiff's injuries, even though the harm to another plaintiff would have been minor.

This rule is also known as the eggshell-plaintiff rule, special-sensitivity rule, or old-soldier's rule.

The thin-skull rule is important because it ensures that defendants are held accountable for the harm they cause, even if the harm is greater than what they could have reasonably foreseen. It also protects vulnerable plaintiffs who may be more susceptible to injury due to their unique physical or mental conditions.