When a caregiver fabricates or intentionally causes symptoms in those they are caring for in order to seek and obtain medical treatment, it is usually a case of

Munchausen syndrome by proxy

Explanation:

Munchausen syndrome by proxy, is a form of child abuse, and is classified as a mental illness. This illness affects the caretaker of a child (in most cases, it affects the mother), where the caretaker will fabricate symptoms or cause visible symptoms so that the child can appear sick.

There is no apparent cause of Munchausen syndrome by proxy, however many people who have this mental illness were either abused as a child, or they have Munchausen syndrome themselves.