The other two core symptoms include cognitive problems or “brain fog,” like trouble with memory and paying attention to details. The other is having issues when you stand up, otherwise known as orthostatic intolerance. You might get dizzy, weak, or lightheaded when you move from a sitting to standing position, or even experience blurriness or spots in your vision.
And although it’s not necessary for a diagnosis, pain in the joints, muscles, or nerves is also very common in people with ME/CFS, Dr. Shepherd says. Other symptoms include a sensitivity to light, sound, odors, and foods; digestive issues; night sweats; and tender lymph nodes in the neck or armpits.
What causes ME/CFS?
ME/CFS actually first started out as just “ME,” or myalgic encephalomyelitis, which refers to muscle pain and inflammation in the brain and spinal cord. It was coined following a 1955 outbreak of the illness in a London hospital. When similar if not identical cases occurred in the US in the 1980s, the CDC recommended the term chronic fatigue syndrome. Today, the two have been combined into ME/CFS as a compromise since some experts and patients felt that CFS didn’t fully capture the seriousness of the disease. As to what causes the symptoms, however, that’s the million dollar question. While experts don’t have a definitive answer at the moment, there are several solid theories.
Infections
So far, viral infections (and sometimes bacterial ones) seem to be the most common trigger of ME/CFS; about 80% of people report that their symptoms emerged after contracting a virus. According to the CDC, roughly 1 in 10 people who come down with Epstein-Barr virus (the microbe behind infectious mononucleosis), Ross River virus (a mosquito-borne illness) or Coxiella burnetti (a type of bacteria that causes Q fever disease) go on to develop an ME/CFS-like sickness. But that’s really just the tip of the iceberg, Dr. Shepherd says. You can develop the condition after having viral meningitis or infections with varicella-zoster virus (which causes chicken pox or shingles), influenza viruses, and coronaviruses such as SARS-CoV-1 and MERS-CoV, which causes Middle East respiratory syndrome (MERS).
Your chances of getting ME/CFS after an infection are higher if you had particularly severe symptoms. However, it’s not clear exactly how viruses may be affecting the body, Hector Bonilla, MD, director of Stanford’s ME/CFS clinic in California, tells SELF. It could be that tiny remnants of the virus remain scattered in the body “like a dust everywhere” long after your infection subsides, Dr. Bonilla says, or perhaps the infection triggers your immune system to go a bit haywire (which we’ll get into in a moment). But lots of people who get this condition don’t appear to have had an obvious infection that could be the culprit, or have encountered other things that might be the trigger. For example, some people have developed ME/CFS after exposure to pesticides and insecticides.
Genetics
Based on cases where multiple family members have developed ME/CFS, researchers think there may be possible genetic factors at play. A few studies have pointed to more than a dozen genes that are associated with major ME/CFS symptoms, including sleep issues and vulnerabilities to stress. However, it’s still not clear if one or more genes are major players here. There’s no predictable pattern of heritability like, say, being born with blue eyes because your mom has them, so more research is needed to better understand this.
Immune system malfunction
It’s possible that the immune system doesn’t know how to turn off after it’s done fighting a virus or responding to physical or emotional stress, Dr. Shepherd says. The result? A bunch of inflammation-causing proteins called cytokines running amok in your body. The higher levels of these cell-signaling molecules are associated with fatigue, Dr. Bonilla says. Some people with ME/CFS also have lower levels of the stress hormone cortisol than healthy people, which can cause inflammation and chronic activation of the immune system.
Changes in your brain
Studies have linked abnormalities in the brain to ME/CFS as well, Dr. Shepherd says, specifically, problems in areas that control movement, sleep, hormone production, and temperature control. That might help explain why people experience such a wide range of symptoms. This is especially important when trying to understand the debilitating fatigue caused by ME/CFS. A study published in February in the journal Nature Communications suggested that fatigue may be caused by a dysfunction in the part of your brain that decides how much effort to exert.
Problems with energy production
Mitochondria are tiny powerhouses inside the body’s cells that act like batteries to give you the energy to function. But in people with ME/CFS, these mitochondria sometimes don’t work properly, according to some research (although the findings have been contradictory). People with long COVID also have similar issues with their mitochondria. “It’s like you’re driving a car with a 40-gallon gas tank. You go everywhere and keep going and going, but when you get [ME/CFS], your gas tank shrinks to about two gallons,” Dr. Bonilla says. “Any activity can consume gas (or energy) and then you crash.”
Who’s at risk for ME/CFS?
The average age of people with ME/CFS is 33, but it can begin as early as age 10 and as late as age 77. Women are up to four times more likely than men to develop the condition, yet it’s not clear exactly why. In general, women are more likely to have autoimmune disorders, so there could be something unique about how their immune systems function, Dr. Shepherd says.
What’s the diagnosis process like for ME/CFS?
Like some other chronic health conditions, there’s no test you can take that will confirm a ME/CFS diagnosis. Although studies have found potential biomarkers in your blood or tissues that may signal you have this condition, there’s no expert consensus as to which ones are the real ones to look for. That’s why more than 9 in 10 people are living with ME/CFS without an actual diagnosis, according to the CDC. “It’s normally a fairly straightforward diagnosis to make when you got a patient with a typical history of viral infection who’s not recovering,” Dr. Shepherd says. “But there are people who don’t quite follow that pattern, and the diagnoses are a bit more difficult to make.”
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