Associated Conditions

In addition to ME/CFS, it is common for people living with ME/CFS to have other conditions, including:

  • fibromyalgia
  • orthostatic intolerance (OI)
  • mast cell activation syndrome (MCAS)
  • Ehlers-Danlos syndrome (EDS)

What is fibromyalgia?

Fibromyalgia is a condition that causes widespread pain and muscle stiffness throughout the body.

How are fibromyalgia and ME/CFS connected?

There is agreement within the medical community that fibromyalgia and ME/CFS are similar conditions, and may be related. However, the major difference between the two conditions is the predominant symptom. Although the two conditions share widespread pain, fatigue and a variety of similar symptoms, their primary features are different. While the primary feature of fibromyalgia is widespread pain, the primary feature of ME/CFS is post-exertional malaise (PEM).

Emerge Australia represents people with ME/CFS who may have a secondary diagnosis of fibromyalgia. If you have received a primary diagnosis of fibromyalgia, Arthritis Australia has a wealth of resources, knowledge and support for your diagnosis.

What are the symptoms of fibromyalgia?

Symptoms of fibromyalgia include:

  • pain across the body, usually described as aching, stiffness and tenderness
  • extreme fatigue
  • difficulties with sleeping
  • problems with concentration and memory
  • headaches

What are the treatments of fibromyalgia?

There is no cure for fibromyalgia. However, with the right approach and management plan, people with fibromyalgia can ease some of the pain and discomfort and enjoy improvements in their quality of life.

What is orthostatic intolerance?

Orthostatic intolerance (OI) is an “umbrella term” for a number of conditions where symptoms are made worse by sitting or standing.

Some definitions that will help you understand OI

  • orthostatic = an upright posture, either sitting or standing
  • tachycardia = fast heart rate
  • hypotension = low blood pressure
  • autonomic nervous system = Your autonomic nervous system controls all of your body functions you don’t need to think about, such as heart rate, blood pressure, breathing and digesting.

There are a number of different forms of orthostatic intolerance, these are:

  • Postural Orthostatic Tachycardia Syndrome (POTS)
  • Orthostatic hypotension (OH)
  • Neurally mediated hypotension (NHH)

What are the symptoms of orthostatic intolerance?

When you stand up, gravity causes an increase in blood to the lower part of your body. In in a healthy person, your autonomic nervous system regulates blood flow very quickly, and you experience no symptoms. In someone with OI, the autonomic nervous system has problems adjusting. This means that there is a decrease in blood flow to other areas of the body.

What are the symptoms of orthostatic intolerance?

  • lightheaded or dizzy when sitting or standing
  • intolerance to heat and/or cold
  • trouble concentrating
  • word finding problems
  • nausea
  • feeling shaky
  • fatigue
  • headache
  • heart palpitations

Often, these symptoms become less or go away completely when you sit or lie down again.

How are orthostatic intolerance and ME/CFS connected?

Orthostatic intolerance is common in people with ME/CFS and can contribute significantly to the level of disability experienced. There is growing awareness that orthostatic stress may also contribute to post-exertional malaise (PEM).

There are many causes of orthostatic intolerance. It is important you work with your doctor to find out if ME/CFS is the cause for you.

Emerge Australia supports people living with ME/CFS who may have a co-diagnosis of orthostatic intolerance. If you have received a primary diagnosis of orthostatic intolerance in any of its forms, Dysautonomia International has a wealth of resources, knowledge and support for your diagnosis.

Are there objective measurements to show you have orthostatic intolerance?

There are some tests your doctor can do in their office to determine if you have orthostatic intolerance. These include:

Testing to see if your heart rate and/or blood pressure change from lying to standing. This is called a NASA lean test
A tilt-table test in a cardiology or neurology department

NOTE: Sometimes tests come back “normal”. However, if you experience problems with sitting and standing, you may still have orthostatic intolerance. Research suggests people with ME/CFS have a 25% decrease in blood flow to the brain on sitting or standing, even when their blood pressure and heart rate measurements are normal1.

What are the treatments for orthostatic intolerance?

There are many different causes of orthostatic intolerance. Treatment and management will depend on the underlying cause. When it is not possible to find the underlying cause, treatment focusses on managing symptoms.

Treatments can be divided into two types, lifestyle management and medication. All treatments should be in consultation with your treating doctor, who knows your medical history and can determine if they are safe for you.

Lifestyle management strategies

  • a high salt diet
  • adequate fluids
  • compression garments – these should be fitted correctly
  • exercise – Exercise is not usually considered safe for people with ME/CFS.
  • Preventing post-exertional malaise should come before any attempt at exercise.
  • mobility aids such as walking sticks or wheelchairs
    use a shower seat as hot water can make the symptoms feel worse

Medication management strategies

There is no “one size fits all” approach to medication. You will need to discuss with your doctor the potential risks and benefits, including other medical conditions such as allergies.

With the right approach and management plan, you can ease some of the disability associated with orthostatic intolerance, which will improve your quality of life. 1. Bateman, L. et al. Myalgic Encephalomyelitis/Chronic Fatigue Syndrome: Essentials of Diagnosis and Management. Mayo Clinic Proceedings 96, 2861–2878 (2021).

What is Mast Cell Activation Syndrome?

Mast cell activation syndrome (MCAS) is a condition where the mast cells in your body, which are part of your immune system, react to triggers that normally wouldn’t cause a problem, producing symptoms of an allergic reaction.

Most people have experienced or know someone with hay fever, hives or anaphylaxis. All three are allergic reactions caused when mast cells release substances called mediators.

What are mast cells?

Mast cells are an important part of our immune system. They are involved in wound healing, building new blood vessels and protecting us from infections. Mast cells are found in most tissues of the body, including bone marrow and around blood vessels. They are especially found in places that interact with the environment, such as your skin, lungs, and gastrointestinal and urinary tract.

MCAS is very different to another condition that involves the mast cells called systemic mastocytosis. With MCAS, the mast cells are ‘overactive’ and it is now thought to be quite common. Mastocytosis is caused by having too many mast cells and it is a rare disorder.

What triggers MCAS?

MCAS can be triggered when you encounter foods, medications, chemicals and environmental exposures, such as hot or cold weather, and pollen. More research is needed to find out why mast cells activate when they don’t need to.

What are the symptoms of MCAS?

MCAS can affect many areas of the body and cause a large number of symptoms that appear to be unrelated. These symptoms include, but are not limited to:

  • fatigue
  • fevers
  • skin – itching, flushing, hives, sweating, swelling and rashes
  • eyes – irritation, itching, watering and redness
  • nose – itching and running
  • mouth and throat – itching, swelling in your tongue or lips, swelling in your throat, dental problems despite good dental hygiene, a sore throat and
  • problems swallowing
  • lungs – trouble breathing and wheezing
  • heart and blood vessels – low blood pressure, rapid heart rate and heart palpitations
  • stomach and intestines – heartburn, cramping, nausea or vomiting, constipation or diarrhea, abdominal pain, and weight loss or gain
  • urinary and reproductive – urinary frequency, urgency, burning, tingling, or stinging, period pain and heavy bleeding
  • nervous system – headache, confusion, anxiety, brain fog and migraines
  • musculoskeletal – pain in muscles and joints that might change or move around.

There is growing awareness that MCAS can produce other symptoms, as well as these common ones.

How is MCAS diagnosed?

Immunologists and haematologists are doctors who specialise in the immune system and blood cells. They should be able to diagnose and treat MCAS, but it is important to make sure that the specialist you see understands MCAS.

Diagnosis of MCAS may involve:

  • ruling out other medical conditions with similar symptoms
  • measuring your level of tryptase, an enzyme that is released from mast cells into the bloodstream during an allergic reaction
  • a 24-hour urine test to measure mast cell mediators.

What are the treatments for MCAS?

If you are diagnosed with MCAS, your doctor will work with you to decide on the best treatment for you.

Some things you can do to help include:

  • identifying and avoiding any known triggers
  • talking with your doctor or a dietician about whether a particular type of diet might be beneficial
  • finding out from your doctor about possible medication options.

If you are experiencing fatigue or symptoms, you feel may be post-exertional malaise (PEM) that is connected to ME/CFS, please review our information on stop rest pace and talk to your doctor about your concerns.

How are MCAS and ME/CFS connected?

MCAS is often linked with hypermobile Ehlers–Danlos syndrome (hEDS), postural orthostatic tachycardia syndrome (POTS) and ME/CFS. It may also be involved in the symptoms of acute and long COVID.

If you believe you have MCAS, it is important to talk with your doctor, as they may need to rule this out as the cause of your symptoms. Some people with ME/CFS can also have MCAS.

Additional resources and references

What is Mast Cell Activation Syndrome (MCAS)?

TMS mast cell disease society, Inc has a lot of information about MCAS.

Weinstock LB, Pace LA, Rezaie A, Afrin LB, Molderings GJ, 2021, ‘Mast Cell Activation Syndrome: A Primer for the Gastroenterologist’, Digestive Diseases and Sciences, vol. 66, issue 4, pp. 965–982. <>

What is Ehlers-Danlos syndrome?

Ehlers-Danlos syndrome (EDS) refers to a group of genetic disorders that involve connective tissue. It is inherited and can affect any part of the body.

Connective tissue is made up of proteins that provide support and structure to tissues and organs. One of these proteins is called collagen. If you have EDS, then you have a problem with the way your body makes collagen, which causes weakness in your connective tissue.

Tissues and organs that can be affected by weak connective tissue include:

  • bone
  • ligaments
  • tendons
  • blood vessels
  • lymphatic vessels
  • the tissue that holds the gastrointestinal tract in place.

What are the symptoms of EDS?

The Ehlers-Danlos Society has an extensive list of symptoms that you may like to read, but some common ones that people with ME/CFS often note when connecting with Emerge Australia include:

  • pain and fatigue
  • joint pain, muscle pain and nerve pain
  • loose or unstable joints that may lead to dislocations
  • muscle tension and weakness
  • weakness of the voice box
  • pelvic floor weakness, bladder or vaginal wall and nerve disorders
  • swallowing difficulties
  • sluggish stomach and large bowel
  • nausea, vomiting, acid reflux, bloating and pain
  • heart rate and blood pressure regulation problems
  • temperature regulation problems
  • systemic inflammation related to mast cell activation

Diagnosis and treatment

“Different tissues and organs can be affected in diverse ways depending on the genetic fault. This explains why there are several subtypes of EDS.” – The Ehlers-Danlos Society 2021

There are thirteen subtypes of Ehlers–Danlos syndrome and most are linked to a gene, except hypermobile Ehlers-Danlos syndrome (hEDS). The type of treatment will depend on the organ that is affected. This is a very specialised area and Emerge Australia recommends seeing a medical specialist who has a deep understanding of connective tissue conditions.

The Ehlers-Danlos Society has a printable diagnostic checklist, but it also notes that the diagnostic criteria is under review.

If you are experiencing fatigue or symptoms that you feel may be post-exertional malaise (PEM) connected to ME/CFS, please review our information on stop rest pace and talk to your doctor about your concerns.

How are EDS and ME/CFS connected?

EDS is often associated with mast cell activation syndrome (MCAS), postural orthostatic tachycardia syndrome (POTS) and ME/CFS. It may also be involved in the symptoms of acute and Long COVID. If you believe you have EDS, it is important to talk with your doctor, as they may need to rule this out as the cause of your symptoms. Some people with ME/CFS can also have EDS.

Additional resources and references

The Ehlers-Danlos Society

Genetic and Rare Disease Network

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