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Harvard Commentaries
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Harvard Commentaries
Reviewed by the Faculty of Harvard Medical School


Medical Myths Medical Myths
 

How Diseases Come and Go


September 25, 2013

By Robert H. Shmerling M.D.

Beth Israel Deaconess Medical Center

You might not think of a disease as something that comes and goes. But it does happen, especially when a condition is poorly understood and has many vague symptoms. Consider neurasthenia, rheumatism and Gulf War syndrome. Each of these was once considered a disease by doctors but has "fallen out of favor." Read on to find out how diseases can get "demoted."

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What Makes a Disease a Disease?

It's not always obvious when a condition becomes a disease. Sometimes great debate and controversy surround a condition. That's especially true for conditions that have multiple, vague and subjective symptoms with normal test results.

In general, here's what makes a condition a disease:

  • The condition is abnormal; it's not typical of healthy people.
  • One or more parts of the body are not working well.
  • The condition has a negative effect on a person's health or puts the person's health at risk.

So, for example, a freckle may not be "normal" skin but it’s not a disease because it does not directly cause or contribute to poor health. And, of course, freckles are common in perfectly healthy people.

Although many diseases are associated with aging, aging itself is also not a disease: sooner or later, it affects everyone and it isn't routinely associated with poor health. Similarly, pregnancy is not a disease – it's part of normal body functioning and is not itself a state of reduced health. Unfortunately, I’ve heard both conditions – aging and pregnancy – called diseases.

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When Is a Disease No Longer a Disease?

A disease can be "demoted" quickly when a new insight, discovery or breakthrough in understanding takes place.

During my medical training in the 1980s, I saw several patients who were terribly ill with a condition called "cryptogenic cirrhosis." These patients had liver failure but the tests for viruses that could cause liver disease were all negative or normal. The term "cryptogenic" was applied because it means "of unknown origin." We now know that many or most cases of cryptogenic cirrhosis were due to a virus called hepatitis C, which had not yet been discovered while I was in training. Now it is much rarer to diagnose someone with cryptogenic cirrhosis.

Another example of improved understanding leading to the demise of a disease is the "Type A personality ulcer." Not long ago, doctors thought that peptic ulcer disease was highly associated with certain personalities. People with Type A personality were driven, ambitious, and impatient. These features were thought to increase stomach acid and, over time, ulcers. We now know that most ulcers are unrelated to personality and are caused by a bacterial infection called H. Pylori or by medications (particularly arthritis and pain medicines called non-steroidal anti-inflammatory drugs, or NSAIDs). While ulcer disease is still very prevalent, a diagnosis of ulcers due to Type A personality has largely disappeared (at least from the vocabulary of healthcare professionals).

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When a Disease Falls Out of Favor

Sometimes a disease will fade from the scene – not because of a new discovery but because medical experts generally agree that the logic underlying the concept of the disease is flawed.

A recent example is "Gulf War syndrome." According to a Veteran's Administration study, up to 30% of soldiers returning from the Gulf War in the early 1990s reported symptoms such as fatigue, memory loss, joint pain and rashes. This combination of problems was quickly called Gulf War syndrome. However, when researchers critically analyzed the problem, they noticed that there was no single combination of symptoms or conditions suffered by these soldiers. The condition still lacks a standard definition.

Other well-established disorders were thought to account for most of their symptoms, including anxiety, depression, chemical exposures (including pesticides and pyridostigmine, an antitoxin for nerve agents) and, in rare cases, amyotrophic lateral sclerosis, a nerve disease commonly called Lou Gehrig's disease. While there were clearly more symptoms among Gulf War soldiers than among those who didn't serve in that war, the findings did not support a single disorder to explain them.

This is important because if a single cluster of problems was repeatedly described, it could suggest a single cause (such as a chemical or toxin exposure) or a single approach to treatment.

A number of previously common conditions have fallen out of favor in this way:

  • Neurasthenia – In the late 1800s and early 1900s, a mysterious condition caused previously healthy people, especially women, to suddenly become unable to function due to fatigue, fainting spells, dizziness and other unexplained symptoms. No cause was known and bed rest was the usual remedy. This condition is no longer diagnosed although some people who are now diagnosed with fibromyalgia, chronic fatigue syndrome or panic attacks would probably have been diagnosed with neurasthenia had it developed 100 years ago.
  • Hypoglycemia – In the past, people with unexplained fatigue or difficulties concentrating were often diagnosed with hypoglycemia (low blood sugar). Most had normal blood sugar when it was actually measured yet the diagnosis was appealing – and popular. The treatment was harmless enough: eating frequent small meals rather than three larger ones each day. Hypoglycemia does occur but nearly always as the result of taking too much of a drug known to lower blood sugar (for example, insulin treatment for diabetes) or rare hormonal disorders. The diagnosis of hypoglycemia without a measured low blood sugar and without a medication to explain it is rarely made now.
  • Rheumatism – Before the 1950s when criteria for rheumatoid arthritis were developed and other types of arthritis were formally categorized, "rheumatism" was diagnosed for a number of painful joint diseases. Rheumatic fever (a complication of a strep infection) accounted for many cases of rheumatism, but rheumatoid arthritis, lupus and many other joint diseases would now be diagnosed instead. In fact, the American Rheumatism Association, the major professional group of rheumatologists in the United States, changed its name to the American College of Rheumatology in recognition of the fact that "rheumatism" has little specific meaning.

Could other conditions currently "in vogue" go the way of rheumatism and neurasthenia? Diagnoses now thought to explain the symptoms of millions of people such as irritable bowel syndrome, fibromyalgia, shin splints and even migraine headaches could be revised someday as advances in medical science improve our understanding of these conditions. Imagine, for instance, if an infectious cause of irritable bowel syndrome were discovered. What if migraine headaches were linked to a vascular birth defect or a genetic mutation? The names (and the treatments) of these common conditions could change in a hurry.

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Conclusion

When a disease falls out of favor, it's important not to assume the disease is not real. The symptoms are quite real to those suffering with them. And just because medical experts are unsure why the symptoms occur, they are no less valid. People sometimes have symptoms that are difficult for medicine to explain. While this may seem surprising, it's because of an underappreciated feature of medicine — its uncertainty. The best doctors and researchers can do is apply concepts, explanations and criteria that seem to fit well, at least until a better explanation comes along and transforms yesterday's common illness into tomorrow's historical curiosity.

Robert H. Shmerling, M.D. is associate physician at Beth Israel Deaconess Medical Center and associate professor at Harvard Medical School. He has been a practicing rheumatologist for over 20 years at Beth Israel Deaconess Medical Center. He is an active teacher in the Internal Medicine Residency Program, serving as the Robinson Firm Chief. He is also a teacher in the Rheumatology Fellowship Program.

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