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Diagnosis of Fibromyalgia

Despite Simple Diagnostic Criteria Misdiagnosis Is Common

Apr 1, 2009 Maija Haavisto

Fibromyalgia is not just a fancy name for chronic pain, it is a specific condition which often causes many symptoms besides pain. It is also frequently misdiagnosed.

Although fibromyalgia is a complex illness, the diagnostic criteria as per the American College of Rheumatology are quite simple - on paper. The diagnosis requires chronic pain in both sides of the body, above and below the waist and in the axial skeleton, such as the spine. In addition, at least 11 of 18 common tender points must be painful (not just tender) on palpation.

Difficulty of Diagnosis

In practice the diagnosis is not so easy. The tenderness of the tender points varies from day to day and it cannot be completely objectively measured. A point one doctor might regard as tender could not be felt as tender enough by another.

Some doctors are not keen on diagnosing fibromyalgia, if the required tender point count isn't satisfied. However, especially considering the low reliability of the tender point exam the patient's symptoms should be considered as a whole instead of focusing on the number of tender points. There are also doctors who consider fibromyalgia as a spectrum, similar to the autistic spectrum.

On the other hand, some physicians label all chronic pain from an unknown cause as fibromyalgia. This is mistaken; fibromyalgia is not a synonym for chronic pain, but a specific medical condition featuring tender points, widespread pain and allodynia (perception of non-painful stimuli as painful).

Most people with fibromyalgia also have other symptoms not included in the diagnostic criteria, such as fatigue, morning stiffness, insomnia, paresthesias (abnormal sensations), cognitive problems ("fibro fog"), urinary frequency, nausea, muscle cramps and problems with balance and coordination. Often it is much more than just pain.

Types of Fibromyalgia

Fibromyalgia can be divided into three subgroups: primary/idiopathic fibromyalgia (no known cause), secondary fibromyalgia (in the presence of autoimmune illnesses) and post-traumatic fibromyalgia (caused by an injury or other physical trauma). Fibromyalgia in children is called juvenile fibromyalgia, though it is usually not considered a specific subtype.

Still, we don't really understand what causes the different types of fibromyalgia, and what difference they make e.g. in prognosis and treatment.

Related Conditions

Fibromyalgia is commonly co-morbid (occurs together) with many other conditions and illnesses, such as osteoarthritis, most autoimmune diseases (especially rheumatoid arthritis, Sjögren syndrome and SLE/lupus) and even cancer, hepatitis and HIV. Other common co-morbidities include e.g.

irritable bowel syndrome (IBS)
migraine
sleep apnea
temporomandibular joint disorder (TMJ/TMD)
interstitial cystitis
vulvodynia and vulvar vestibulitis
restless legs syndrome (RLS)
multiple chemical sensitivity (MCS)
Raynaud's phenomenon
Lyme disease

To confuse things further, many co-morbid conditions can cause symptoms very similar to fibromyalgia by themselves. E.g. the symptoms of chronic fatigue syndrome/myalgic encephalomyelitis (CFS/ME) can be nearly identical to those of fibromyalgia, but both conditions also commonly occur in the same people.

Fibromyalgia Misdiagnosis

The medical literature contains many reports of people who have been diagnosed as having fibromyalgia, but have turned out to have another illness such as muscular dystrophy, Lyme disease or osteomalacia (softening of the bones). Turkish researchers have suggested that some "borderline" fibromyalgia cases may be due to joint hypermobility - but joint hypermobility is also a risk factor for fibromyalgia.

It is now recognized that vitamin D deficiency, which can lead to osteomalacia, can cause symptoms very similar to fibromyalgia. Many people with a diagnosis of fibromyalgia respond well to thyroid and/or cortisol (hydrocortisone) supplementation. With hormonal conditions like this, it is often difficult to define whether they are subtypes of fibromyalgia or merely mimic it.

Some of the illnesses misdiagnosed as fibromyalgia may be serious, others would be easily treatable (or even curable) and as such it is tragic to miss them. Even when the diagnosis appears certain, one has to pay careful attention to any new symptoms. Pain and other symptoms caused by another serious illness such as cancer can be mistakenly attributed to the fibromyalgia, with devastating results.

References

Karaaslan Y, Haznedaroglu S, Oztürk M. Joint hypermobility and primary fibromyalgia: a clinical enigma. J Rheumatol. 2000 Jul;27(7):1774-6.

The copyright of the article Diagnosis of Fibromyalgia in General Medicine is owned by Maija Haavisto. Permission to republish Diagnosis of Fibromyalgia in print or online must be granted by the author in writing.