Sunday, January 18, 2009

The Distributed Knowledge of Medicine

The recent entry “A doctor’s view on diagnosis” reveals the challenges that physicians and their patients experience in the face of an unknown diagnosis. John’s situation is regrettably common: being sent to multiple doctors with none able to render a convincing or actionable diagnosis. This leaves the physician and patient emotionally drained and despondent, feeling as if there is no one who can help.

A counterbalance to complete despair is every physician’s first hand or anecdotal knowledge of a seemingly unsolvable case spanning months or years of evaluations, testing, and treatment that is suddenly and unexpectedly diagnosed. Frequently this change of fortune comes about by crossing paths with a single doctor. Fans of Fox’s House will recognize this as a weekly phenomenon. The opening chapter of Jerome Groopman’s How Doctors Think vividly outlines this occurrence, highlighting the weariness on the part of both the patient and the physician in perusing yet another referral and culminating in the diagnosis of celiac sprue, a prevalent but perpetually under-recognized illness. Recently, a young woman suffered from hearing loss, urticaria, and arthritis for decades until she walked into the office of my colleague who recognized the very rare Muckel Well’s syndrome. Relief from a lifetime of pain came within days by instituting treatment with an interleukin-1 receptor antagonist.

In the New England Journal of Medicine weekly case report, expert diagnostic discussions of challenging cases are presented. The point is made on multiple occasions (see June 26, July 3, and August 14, 2008) -- and with refreshing honesty -- that the case was solved on account of the consulting physician’s experience with the disease in question. After 9 years of thirst, insomnia, fatigue, arthralgias, and endocrine abnormalities followed by the development of radiographic abnormalities in the pituitary gland, cerebellum, and aorta, Dr. John A. Mills of the Rheumatology, Allergy, and Immunology Division of Massachusetts General Hospital made the very rare diagnosis of Erdheim–Chester disease (a type of histiocytosis) (

At the conclusion, the following exchange occurs between the physicians at the conference:

Dr. Harris: This patient saw internists, neurologists, and ophthalmologists in his home town, and at [Harvard University’s Massachusetts General Hospital] he saw two neuro-oncologists, a neuro-endocrinologist, and a hematologic oncologist. He also saw another rheumatologist after the biopsy results were available and before seeing Dr. Mills. Experienced pathologists did not consider this diagnosis when the biopsy specimen was first seen. In retrospect, the lesions seen on radiography that suggested the diagnosis to Dr. Mills had been present for several years, but their significance was not appreciated….This experience tells us that the diagnosis of histiocytoses can be remarkably difficult, even with all our available expertise and technology.

A Physician: It seems that this case has lessons for radiologists, pathologists, and internists. Dr. Mills, since most of us here are internists, what lessons should we draw from this case to make us better able to recognize this type of disorder sooner?

Dr. Mills: I was aware of this condition because I have been interested in vasculitis and particularly in aortitis…I have seen several patients with Erdheim–Chester disease who were referred to me with a diagnosis of aortitis, as this patient was. If you had not read literature on this disease, it is unlikely that you could have arrived at the diagnosis.

Whenever I observe this type of insight (and the circumstances that bring together the patient with that particular physician), I recall my challenging cases and think to myself that there must be somebody who recognizes the collection of signs and symptoms that evades diagnosis by me, my network of colleagues, and even Google. I am reminded that there is often a physician whose specific knowledge and experience -- which may derive from a single patient seen years ago or from their lifetime’s work -- holds the key for an undiagnosed patient.

The collective knowledge of human medicine and the experiences and insights of the worldwide medical community are vast. Medical science can be described as a distributed knowledge ( it is the union of all the knowledge of individuals in a community, which is far more than any one physician, hospital, university, or geographic locale can possess.

A great challenge is determining how to harness this knowledge and make it accessible for physicians who are faced with diagnostic dilemmas. Isabel ( and other diagnostic support systems are one way to connect to this distributed knowledge network. Physician interaction through the internet, essentially replicating the familiar curbside consultation many times over, is another promising way to connect a patient’s case with the appropriate physician. If these sorts of efforts were undertaken with regularity, it is possible that the solutions to difficult cases would come about not by serendipity, as in the instances described above, but rather by systematic and deliberate access to the global medical community’s knowledge and talent.


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