Munchausen syndrome by proxy (MSBP) is rare. The true number of cases is unknown.

Children subjected to MSBP are most often younger than 6 years old. But MSBP has also involved older children, including teens. Older children and teens subjected to this syndrome may cooperate with the offending caregiver. For example, they may tell the doctor what the caregiver has told them to say, or they may truly believe they have an illness.

Often several children in one family will be victims of MSBP, although usually the caregiver with MSBP abuses only one child at a time.

The long-term effects on victims of MSBP vary depending on the severity of abuse and the treatment. Some children die from the abuse, although the exact number is hard to determine.