How Diseases Come and Go
Last reviewed on October 23, 2012
By Robert H. Shmerling, M.D.
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."
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:
So, for example, a freckle may not be "normal" skin but its 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, Ive heard both conditions aging and pregnancy called diseases.
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).
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. Other well-established disorders were thought to account for most of their symptoms, including anxiety, depression 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:
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.
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.