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Overlapping Conditions with Chronic Fatigue Syndrome & Myalgic Encephalomyelitis


By Erica Verrillo*

Patients with ME/CFS commonly experience one or more conditions that may appear simultaneously with ME/CFS, occur prior to a diagnosis of ME/CFS, or appear years later. Some of these, like fibromyalgia, have symptoms that are so similar to ME/CFS that it is hard to distinguish between them. Others, like migraines, may only appear in a subset of ME/CFS patients.

When conditions overlap it is often difficult to make an accurate diagnosis. Some patients discover years after their ME/CFS diagnosis that they have a different illness entirely. Often these are illnesses for which treatment is available.

If you have symptoms of easy fatigability, exercise intolerance, painful joints or muscles, or sleep disturbance, do not automatically assume that you have ME/CFS, as these are symptoms common to a number of ailments.

Illnesses with Symptoms Similar to ME/CFS

Patients with the following illnesses can be misdiagnosed with ME/CFS. These illnesses may be difficult to detect in their early stages, and will require a specialist for proper diagnosis. All of these illnesses, as well as others, have been missed by physicians who have treated patients misdiagnosed with ME/CFS.

Chronic Fatigue Syndrome and Multiple Sclerosis

Multiple Sclerosis

Up to one-third of American patients with MS have been misdiagnosed with CFS, because the predominant symptom in early MS is fatigue (Berger et al).

If you have any neurological symptoms indicative of MS, be sure to see a specialist.

Chronic Fatigue Syndrome and Ehlers-Danlos Syndrome

Ehlers-Danlos Syndrome

EDS is a genetic connective tissue disorder that produces pain, fatigue, unrefreshing sleep, and cognitive impairment – all of which are common symptoms of ME/CFS.

Joint hypermobility is a cardinal symptom of EDS.

Chronic Fatigue Syndrome and Myasthenia Gravis

Myasthenia Gravis

Myasthenia gravis is an autoimmune neuromuscular disease that produces weakness of the skeletal muscles. Characteristic symptoms include drooping eyelids, trouble chewing or swallowing, difficulty speaking, or holding up the arms or head. The weakness may come and go, but the illness is progressive. If you find that muscle weakness is predominant, or becomes worse over time, be sure to see an immunologist.

Chronic Fatigue Syndrome and Mitochondrial Disease

Mitochondrial Disease

Mitochondrial Disease is a genetic disorder passed down through the mother. It appears fairly early in life. The primary symptoms of Mitochondrial Disease are exercise intolerance, easy fatigability, loss of coordination, weakness, neurological symptoms, pain, IBS, and slow growth.

If your child has these symptoms and there is a family history on the mother’s side make sure to rule out mitochondrial disease.

Chronic Fatigue Syndrome and Hypopituitarism


Injury to the pituitary gland will cause all of the major symptoms of ME/CFS, including fatigue, pain, weakness, and headache. If symptoms appear after a concussion or other head trauma, or after an infection involving the brain or nervous system (encephalitis), tests for low pituitary hormones or an MRI to detect a shrunken pituitary gland are in order.

Chronic Fatigue Syndrome and Lyme disease

Lyme disease

Lyme disease that is not resolved by antibiotics can become chronic.

Roughly 10 to 15 percent of people who are treated for Lyme disease develop persistent symptoms of fatigue, muscle pain and cognitive impairment.

Chronic Fatigue Syndrome and Behçet's disease

Behçet’s disease

Behçet’s (pronounced “beh- SHETS”) is an autoimmune disease that causes inflammation in the blood vessels.

Canker sores or ulcers in the mouth are a hallmark of the disease, but inflammation in parts of the eye, painful joints, skin problems, and inflammation of the digestive tract, brain, and spinal cord can also arise as the disease progresses.


When an illness or condition is experienced alongside another illness it is called a comorbidity. Comorbidities are so common in the ME/CFS patient population that it is rare to find a patient who does not have several (Aaron et al).


The most common overlapping condition with ME/CFS is fibromyalgia. In ME/CFS dominant patients, the fibromyalgia pain is not constant, but tends to appear when there is an additional injury or infection, such as an accident, a viral infection, or a surgical procedure. Fibromyalgia is a syndrome, with many symptoms in addition to pain. But, if pain is not present, the patient cannot receive a diagnosis of fibromyalgia.

Other related pain syndromes that may appear with ME/CFS are:

  • Temporomandibular disorder (TMJ) – A painful condition caused by dysfunction in the jaw joint and the muscles that control jaw movement.
  • Chronic pelvic pain – This is a condition experienced by women in which pain is experienced below the navel. Many conditions can lead to chronic pelvic pain, including endometriosis, infections of the ovaries, irritable bowel syndrome and various hormonal irregularities.
  • Chronic nonbacterial prostatitis – Experienced by men, and, as with pelvic pain in women, may result from a number of causes, such as bicycle riding, viruses, parasites, and neurological problems.
  • Interstitial Cystitis – IC is a painful condition that mimics the symptoms of ordinary cystitis, but without bacterial infection. According to Dr. Larrian Gillespie, author of You Don’t Have to Live With Cystitis, IC is caused by the erosion of the GAG layer, which is the mucous lining that protects the bladder from its contents. Mast cell activation, an immune process, is believed to be the driving force that leads to the erosion of the GAG layer (Theoharides et al).

Autoimmune Disease

It has been proposed that ME/CFS is an autoimmune disorder, because it shares distinctive chemical markers with other autoimmune diseases (Staines et al). Clinicians have observed that a diagnosis of ME/CFS may precede a diagnosis of autoimmune disorder, which means that either the correct diagnosis was initially missed, or that the patient subsequently developed an autoimmune disease. The following are some autoimmune diseases that most frequently occur as comorbidities with ME/CFS.

  • Hashimoto’s Disease – Dr. John Richardson noted that among his ME patients, 20% developed Hashimoto’s disease, an autoimmune disease that affects the thyroid. Patients with Hashimoto’s disease often have normal lab results, so the diagnosis may be missed for several years.
  • Sjögren’s Syndrome – An autoimmune disease that causes dry mouth and eyes, along with other symptoms
  • Lupus – An autoimmune disease that can damage any part of the body (skin, joints, and/or organs inside the body). Lupus is characterized by a distinctive face rash resembling a wolf, from which the disease gets its name.


Headaches of a new variety or severity are experienced by upwards of 75% of the patient population according to Dr. Katrina Berne. Some patients suffer from these headaches daily.

The most common variety of headache experienced by ME/CFS patients is migraine, which is found in 60-84% of patients with ME/CFS (Ravindran et al).

Multiple Chemical Sensitivity

Multiple Chemical Sensitivity (MCS) produces a severe reaction to many different kinds of pollutants including solvents, VOC’s (Volatile Organic Compounds), perfumes, petrol, diesel, smoke, and other chemicals. In a five-year study of 690 patients conducted by Dr. Dedra Buchwald, more than 50% of patients with ME/CFS reported having chemical sensitivities. Research conducted by I. R. Bell in 1998 showed a similar percentage. A 2000 study by Jason et al. found that roughly 40% of patients with ME/CFS also met the criteria for multiple chemical sensitivities (MCS).

The symptoms of MCS are wide-ranging and may include burning and stinging eyes, wheezing, breathlessness, nausea, extreme fatigue/lethargy, headache/migraine/vertigo/dizziness, poor memory and concentration, runny nose (rhinitis), sore throat, cough, sinus problems, skin rashes and/or itching skin, sensitivity to light and noise, sleeping problems, digestive upset, and muscle and joint pain.

Orthostatic Intolerance and Postural Orthostatic Tachycardia Syndrome (POTS)

Many, if not most, patients with ME/CFS report problems standing (orthostatic intolerance). Orthostatic intolerance (OI) is a broad classification referring to exaggerated blood pressure and/or heart rate responses that occur when standing up. When a healthy person stands up, the effects of gravity cause about 10-15% of the blood to settle (pool) in the abdomen, legs, and arms. To make up for the reduced amount of blood returning to the heart, the adrenal glands release adrenaline and noradrenaline (epinephrine and norepinephrine), which cause the heart to beat a little faster and blood vessels to constrict.

People with OI have reversed responses to changes in position. When people with OI stand up, they pool a larger amount of blood in regions below the heart. The longer they remain upright, the more blood pools in their abdomen and legs. The adrenal glands respond by releasing more adrenaline and noradrenaline in an attempt to cause constriction of the blood vessels and boost cardiac output.

However, the blood vessels do not constrict enough to ensure increased back flow into the heart, and the heart races. This, in turn, leads to lower blood volume (hypovolemia), which perpetuates the cycle.

The symptoms produced by this loop are fatigue, nausea, light-headedness, heart palpitations, sweating, and sometimes fainting (syncope). The feedback loop that leads specifically to an increased heart rate of 30 bpm (beats per minute) or more when standing is called POTS – postural orthostatic tachycardia syndrome.

According to Dr. Julian Stewart, director of the Center for Hypotension at the New York Medical College, “orthostatic intolerance in most adolescents (and many adults) with CFS appears to be POTS.” OI/POTS is so common in the patient population that Hoad et al. have recommended that the response to standing should be a diagnostic marker for ME/CFS.

* Erica Verrillo is ProHealth’s expert editor for the ME/CFS HealthWatch and Natural Wellness newsletters. She is the author of Chronic Fatigue Syndrome: A Treatment Guide, 2nd Edition, available as an electronic book on Amazon,Barnes & Noble, Kobo and Payhip (PDF file). Her website,, provides practical resources for patients with ME/CFS. She also writes a blog, Onward Through the Fog, with up-to-date news and information about the illness, as well as the full text of CFS: A Treatment Guide, 1st Edition (available in translation).


Further Reading

How doctors are failing to spot the brain injury that could be behind 30,000 cases of ‘chronic fatigue’

Brownout: The Mitochondria Detective Work Gets a Little Easier

United Mitochondrial Disease Foundation

When Lyme Disease Lasts and Lasts

Sjögren’s Syndrome Foundation

The Lupus Foundation of America

Multiple Chemical Sensitivity

Postural tachycardia syndrome (POTS)



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