Some of literature's most beloved characters thrive by cunningly misleading others (Odysseus, Don Juan, and Tom Sawyer come to mind). Yes, we scorn liars and con men, but we also celebrate those who have mastered the art of lies.
Some of the most befuddling and tragic "con men" a doctor will see are those with Munchausen syndrome, who intentionally exaggerate, induce, or simulate illness or injury, in order "to assume the sick role." Munchausen syndrome by proxy occurs when someone intentionally induces or simulates injury in another (typically their child).
Diagnosing a patient can sometimes be like answering a trick question: the ordinary rules don't always apply. A case report in the NEJM reads like a detective story. A healthy-seeming toddler presented to a clinic because of a "reported febrile convulsion." Blood samples were taken on several occasions and given to the patient's mother, who dropped them off at the laboratory for processing. Each one showed potassium and creatinine levels so high as to be "incompatible with life." This apparently piqued the interest of the physicians, who recognized that the readings were factitious (not reflective of reality).
The doctors readminstered the blood test and gave the mother two blood samples with her daughter's name on it--except that one secretly contained a different patient's blood whose lab values were known. Sure enough, both blood samples came back with impossibly high potassium and creatinine levels.
The physicians knew of another bodily fluid that naturally contains lots of potassium and creatinine. By estimating how much the blood had been diluted, the physicians calculated just how much urine had been introduced into each vial. The mother denied any wrongdoing when confronted by a psychiatrist, and child protective services intervened.
Other horror stories abound--patients who inject saliva, water, and even feces into their bloodstream, mothers (most people with Munchausen syndrome are females) who repeatedly suffocate their children. The diagnosis is extremely difficult to make, because the patient is deftly and secretly conspiring against the doctor.
The physicians in the case I described put it well: "It seems that in the case of Munchausen-by-proxy syndrome, the perpetrator may be more creative than physicians can imagine."
