A retrospective diagnosis (also retrodiagnosis or posthumous diagnosis) is the practice of identifying an illness in a historical figure using modern knowledge, methods and disease classifications. Alternatively, it can be the more general attempt to give a modern name to an ancient and ill-defined scourge or plague.
Retrospective diagnosis is practised by medical historians, general historians and the media with varying degrees of scholarship. At its worst it may become "little more than a game, with ill-defined rules and little academic credibility." The process often requires "translating between linguistic and conceptual worlds separated by several centuries", and assumes our modern disease concepts and categories are privileged. Crude attempts at retrospective diagnosis fail to be sensitive to historical context, may treat historical and religious records as scientific evidence, or ascribe pathology to behaviours that require none. The understanding of the history of illness can benefit from modern science. For example, knowledge of the insect vectors of malaria and yellow fever can be used to explain the changes in extent of those diseases caused by drainage or urbanisation in historical times.
The practice of retrospective diagnosis has been mocked in parody, where characters from fiction are "diagnosed". Squirrel Nutkin may have had Tourette syndrome and Tiny Tim could have suffered from distal renal tubular acidosis (type I).
The term retrospective diagnosis is also sometimes used by a clinical pathologist to describe a medical diagnosis in a person made some time after the original illness has resolved or after death. In such cases, analysis of a physical specimen may yield a confident medical diagnosis. The search for the origin of AIDS has involved posthumous diagnosis of AIDS in people who died decades before the disease was first identified. Another example is where analysis of preserved umbilical cord tissue enables the diagnosis of congenital cytomegalovirus infection in a patient who had later developed a central nervous system disorder.
- Was the English sweat caused by hantavirus?
- Was the black death due to bubonic plague?
- Was "the great pox" syphilis or several venereal diseases?
- Did Napoleon die from stomach cancer, or was he poisoned with arsenic?
- Could Franklin D. Roosevelt's paralytic illness have been Guillain-Barré syndrome rather than poliomyelitis?
- Did botulism cause the religious visions experienced by Julian of Norwich?
- Did King George III of the United Kingdom exhibit the classic symptoms of porphyria?
- Did Abraham Lincoln have Marfan syndrome?
- Could Burke and Wills have died of thiaminase poisoning?
- Did Tutankhamun have Klippel-Feil syndrome?
- Did Abraham, Moses, Jesus or Saint Paul have psychotic spectrum psychological symptoms?
 See also
- Samuel Johnson's health
- Charles Darwin's illness
- List of people with epilepsy (includes notes on retrospective diagnosis and misdiagnosis of historical figures)
- Historical figures sometimes considered autistic
- "MedTerms: Retrodiagnosis". MedicineNet.com. 2004-01-12. Retrieved 2008-08-08.
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