How do Munchausen syndrome and Munchausen syndrome by proxy differ?

Munchausen syndrome is a chronic factitious disorder in which patients totally fabricate their symptoms, self-inflict lesions, or exaggerate or exacerbate a preexisting physical condition. The motive for the behavior remains unclear. Unfortunately, the disorder often leads to multiple hospital admissions and unnecessary procedures, surgery, and laboratory studies. When confronted with evidence that the symptoms are factitious, patients usually deny the allegations and leave against medical advice, only to repeat their actions in another hospital, city, state, or country.

In Munchausen syndrome by proxy, a third party facilitates an illness in another individual, usually a child, and receives some vague secondary gain from the behavior.

Falagas ME, Christopoulou M, Rosmarakis ES, Vlastou C: Munchausen’s syndrome presenting as severe panniculitis, Int J Clin Pract 59:504–505, 2005.