Of Zebras, Rare Diseases, and Google

When you hear hoof beats behind you, don’t expect to see a zebra.

Medical aphorism on the rarity of rare diseases

A rare or "orphan" disease affects fewer than 200,000 people in the United States. There are more than 6,000 rare disorders that, taken together, affect approximately 25 million Americans.

National Organization for Rare Disorders (NORD)

I have been asked to speak before a group of seniors about rare diseases. The thought fills me with trepidation. I am not an expert on rare diseases. There are so many of them. I fear being misquoted or misunderstood. I worry about malpractice implications, even though I am no longer in practice.

Nevertheless I am going to give the seniors my two cents worth, which is about what my opinion is worth. The temptation is irresistible. “To talk of diseases,” as Sir William Osler said, “is a sort of Arabian Nights entertainment.”

This sort of entertainment appeals to doctors. Just ask me. For me, the popular feature of the New England Journal of Medicine is its section “Case Records of the Massachusetts General Hospital,” which weekly discusses rare and mysterious diseases. I turn to it first when I read the Journal.

Diagnosing rare diseases is a combination of experience, intuition, triangulation, thought association, exclusion, knowledge, serendipity, and listening to the patient. A store of obscure and arcane information on rare or exotic syndromes helps a bit too. Making diagnoses is especially tough in multisystem diseases with vague symptoms that come and go, or in diseases for which there is no definitive diagnostic test or biopsy.

To complicate matters, the Internet has produced a generation of "cyberchondriacs,” who imagine they have every disease imaginable. Managed care and economic pressure compelling doctors to see a new patient every 10 minutes to so to make ends meet compounds diagnostic dilemmas.

Many Internet geeks believe new-fangled algorithms and diagnostic support systems at the point of care will resolve most diagnostic mysteries or at least point the right direction.

Jerome Groopman, MD, a distinguished diagnostician at Harvard Medical School, is not so sure. In his book How Doctors Think (Hougton Mifflin, 2007), he says,

“Clinical algorithms can be useful for run-of-the-mill diagnosis and treatment – distinguishing strep throat from viral pharyngitis, for example. But they quickly fall apart when a doctors needs to think outside their boxes, when symptoms are vague, or multiple and confusing or when test results are inexact. In such cases – the kinds of cases where we most need a discerning doctor – algorithms discourage physicians from thinking independently and creatively. Instead of expanding a doctor’s thinking, they constrain it.”

“Similarly, a movement is afoot to base all treatment decisions strictly on statistically proven data. This so-called evidence-based medicine is rapidly becoming the cannon… But today’s rigid reliance on evidence-based medicine risks having the doctor chooses care passively, solely on the numbers. Statistics can’t substitute for the human being before you; statistics embody averages, not individuals.”

In the main, Groopman is right. But computer diagnosis, particularly on Google, has a place. Articles in the British Medical Journal (Tang.H, and Nu, J, “Googling for a Diagnosis- Use of Google as a Diagnostic Aid- An Internet-Based Study, November 10, 2006) and the New England Journal of Medicine (Greenwald, R, “…And a Diagnostic Test Was Performed, ”November 10, 2005) indicate a Google search may quickly reveal the diagnosis of a rare disease. Google does this through its Page Rank algorithm. A correct hit on Google is called a “Ghit."

The zebras are out there, but don’t look for them first.


Richard L. Reece, MD, has posted 1750 blogs at medinnovation blog over the past 4 1/2 years. His main themes concern health reform and innovation and how they impact physicians and American culture as a whole. He works closely with the Physicians Foundation, but his opinions are his alone. He has written eleven books. His latest book, The Health Reform Maze, is now at Greenbranch Publishing and will be released in June. Doctor Reece’s website, www.doctorreece.com, is now up and running He invites comments and questions on his blog and will respond to each comment or question on his blog or to him directly at 860-395-1501 or rreece1500@aol.com