The elements of differential diagnosis of fibromyalgia including differentiation with candidosis and reactive depression has been presented in different sections of this service. The diagnostic criteria of fibromyalgia syndrome that should be taken into consideration when differentiating diagnosis are presented in the section »Diagnosis« of the main menu.

Remember! Diagnosis of fibromyalgia has to be established by physician and even if you are convinced that you have fibromyalgia symptoms you should visit your doctor to be sure.


The cardinal feature of fibromyalgia (FM) is chronic, widespread pain, not explained by another rheumatic or systemic disorder. Explicit in this definition is the exclusion of other conditions that can present with widespread pain. Thus, although the differential diagnosis of FM may potentially become quite complicated, it should actually be relatively simple. Rather than worrying about every disease that can cause musculoskeletal pain, the clinician should focus on the characteristic features of fibromyalgia:

  • Pain above and below the waist, bilateral and axial for at least three months and
  • Somatic complaints including fatigue and sleep, mood, and cognitive disturbance.

These symptoms are often present in many other diseases. However, these other conditions, such as infection, are often either transient or manifest abnormal physical and laboratory findings. In fibromyalgia, the physical examination, other than tenderness in muscles and soft tissue (tender points) is unrevealing and laboratory and imaging are unremarkable.

The conditions that should be taken into consideration in differential diagnosis of fibromyalgia include disorders that could mimic fibromyalgia or appear as comorbid diseases and a collection of common disorders that often overlap with fibromyalgia. These latter illnesses are common and can present challenges in differential diagnosis. They include: myofascial pain syndrome1 (MPS), sciatica pain2, chronic fatigue syndrome (CFS), irritable bowel syndrome (IBS), temporomandibular pain3 (TMD), pelvic and bladder pain disorders (OAB) symptoms from genitourinary system. ]. Like fibromyalgia, each of these conditions is very common and controversial, since there are no objective abnormalities found on the physical, laboratory, or radiologic examinations. As a result, fibromyalgia and these overlapping disorders are often termed "functional somatic syndromes."

1 Musculoskeletal disorders (MSDs) are injuries or pain in the human musculoskeletal system, including the joints, ligaments, muscles, nerves, tendons, and structures that support limbs, neck and back. MSDs can arise from a sudden exertion (e.g., lifting a heavy object), or they can arise from making the same motions repeatedly repetitive strain, or from repeated exposure to force, vibration, or awkward posture. Injuries and pain in the musculoskeletal system caused by acute traumatic events like a car accident or fall are not considered musculoskeletal disorders. MSDs can affect many different parts of the body including upper and lower back, neck, shoulders and extremities (arms, legs, feet, and hands). Examples of MSDs include carpal tunnel syndrome, epicondylitis, tendinitis, back pain, tension neck syndrome, and hand-arm vibration syndrome.

2 Sciatica is a medical condition characterized by pain going down the leg from the lower back. This pain may go down the back, outside, or front of the leg. Onset is often sudden following activities like heavy lifting, though gradual onset may also occur. Typically, symptoms are only on one side of the body. Certain causes, however, may result in pain on both sides. Lower back pain is sometimes but not always present. Weakness or numbness may occur in various parts of the affected leg and foot.

3 Temporomandibular joint dysfunction (TMD, TMJD) is an umbrella term covering pain and dysfunction of the muscles of mastication (the muscles that move the jaw) and the temporomandibular joints (the joints which connect the mandible to the skull). The most important feature is pain, followed by restricted mandibular movement, and noises from the temporomandibular joints (TMJ) during jaw movement. Although TMD is not life-threatening, it can be detrimental to quality of life, because the symptoms can become chronic and difficult to manage.

Introduction to the Differential Diagnosis

Initial approach to the differentiation diagnosis of person with complains suggesting fibromyalgia consists of thoroughly collected medical history (interview) and physical examination. The initial blood test should cover: blood morphology, blood sedimentation rate (ESR), biochemistry (sugar, creatine, electrolytes (including calcium and magnesium), inflammatory markers: C-reactive protein (CRP) and plasma viscosity (PV) and thyroid hormones (TSH). These tests are usually normal in fibromyalgia and abnormality may suggest any of below systemic diseases.

Systemic Diseases and Rheumatic Diseases Mistaken with Fibromyalgia

Fibromyalgia might be diagnosed by error as one of several systemic and rheumatic diseases just to mention: rheumatoid arthritis (RA), Sjögren syndrome (SjS), systemic lupus erythematosus (SLE). One can experience general (polyarticular) arthralgia* and myalgia** and chronic tiredness and similar as in fibromyalgia often affects women in younger age. However, in case of rheumatoid arthritis many joints are affected and in case do SLE the characteristic face redness (butterfly shape erytheme) and multiple organ disorders occur, which never happens in fibromyalgia.

Carefully collected anamnesis (medical history) and thorough medical examination should be more effective than blood screening tests in differentiation between fibromyalgia and systemic connective tissue diseases. As long as there is not a strong and substantial presumption of systemic rheumatic disease a routine performance of blood serological tests is not recommended. The ANA tests (anti-nuclear antibodies) and/or RF test (rheumatoid factor) can be false positive in healthy people and in several other disorders. For example 10 to 15 percent of fibromyalgia patients has positive ANA test. (Dinerman H, Goldenberg DL, Felson DT. A prospective evaluation of 118 patients with the fibromyalgia syndrome: prevalence of Raynaud's phenomenon, sicca symptoms, ANA, low complement, and Ig deposition at the dermal-epidermal junction. J Rheumatol 1986; 13:368.)

*arthralgia – joint pain. It can be limited to one joint (monoarticular) and several joints (polyarticular) or general arthralgia.

**myalgia – muscle pain can be a symptom of many diseases and disorders. The most common causes are the overuse or over-stretching of a muscle or group of muscles. Myalgia without a traumatic history is often due to viral infections. Longer-term myalgias may be indicative of a metabolic myopathy, some nutritional deficiencies or chronic fatigue syndrome.

Please notice!

Here you may download a form → new diagnostic criteria for fibromyalgia, (pdf file), that may help you to find out if you have fibromyalgia. It helps to calculate value of Widespread Pain Index (WPI) and Symptoms Severity score (SS score). The form has built-in sending function that could be executed if your computer has an active internet connection. You may send your questionnaire to our medical consultant if you want to get his opinion.

Caution: Make sure that filled up questionnaire is saved to hard disc of your own computer before sending. Give this file its own name, and send us such document. It is about saving the choices and data and/or not to lose or mistaken your document with other questionnaire that has identical name.

Fibromyalgia occurs more frequently in persons suffering from systemic immunologic diseases as compared to the general population. This has been illustrated by results of studies listed belowed:

According to the American College of Rheumatology coexistence of other illness does not exclude diagnosis of fibromyalgia. The symptoms of other illnesses may mimic fibromyalgia symptoms. In the table below we have presented differentiation between some more important and frequent diseases that symptoms may mimic or resemble fibromyalgia. One must not forget that fibromyalgia is a non-inflammatory condition.

Selected symptoms observed in fibromyalgia and other diseases Differentiation Symptoms not present in fibromyalgia
Joint pain, feeling of oedema and stiffness Inflammatory rheumatic diseases Joint oedema objectively confirmed, ↑ ESR and CRP
Widespread muscle pain, stiffness Rheumatic polymyalgia ↑OB, anaemia, body mass reduction
Tiredness and muscle weakness Polymyosistis (PM) Muscle weakness limited to shoulder and pelvic girdle, ↑OB and ↑activity of muscle enzymes
General fatigue, muscle pain Chronic Fatigue Syndrome (CFS) Subfebrile stages, pharyngitis, lymph nodes enlargement and soreness
Tiredness, cold intolerance, joint and muscle pain Hypothyroidism Reduced thyroid hormone level (T4) increased TSH level
Back pain, stiffness Ankylosing spondylitis and other spondyloarthropathies Restricted spine mobility in thoracic and lumbo-sacral part, X-ray changes in sacroiliac joints
Back pain, increased muscle tonus Discopathy Neurological symptoms, X-ray and NMR changes
Paresthesiae Neuropathy Neurological symptoms, neuronal conduction disorders
Cold hands/feet, dry mouth, immune disorders Systemic diseases of connective tissue ↑ESR, other symptoms of systemic diseases, changes in immune tests
Intermittent pain in tendons, muscles, joints, and bones, tiredness Lyme Disease Exposure to tick bites, erhythema migrans, positive serological tests and inflammation markers

ESR - erythrocyte sedimentation rate, CRP - C reactive protein, T4 - Thyroxine, major thyroid hormoone - called T4 because it contains four iodine atoms, NMR - nuclear magnetic resonance


Spondyloarthropathy or spondyloarthrosis is the name for a family of inflammatory rheumatic diseases that cause arthritis of the spine. As such, it is a class or category of diseases rather than a single, specific entity. It differs from spondylopathy, which is a disease of the vertebra itself. It may affect the joints of the arms and legs in some people. It can also involve the skin, intestines and eyes. The main symptom (what you feel) in most patients is low back pain. This occurs most often in axial spondyloarthritis.

People in their teens and 20s, particularly males, are affected most often. Family members of those with spondyloarthritis are at higher risk. Many people with axial spondyloarthritis progress to having some degree of spinal fusion, known as ankylosing spondylitis. This more often strikes young males.

Spondyloarthritis (or spondyloarthropathy) differs from other types of arthritis, because it involves the sites are where ligaments and tendons attach to bones called "entheses". Symptoms present in two main ways. The first is inflammation causing pain and stiffness, most often of the spine. Some forms can affect the hands and feet or arms and legs. The second type is bone destruction causing deformities of the spine and poor function of the shoulders, hips, and chest.

If you would like to read more about ankylosing spondylitis and another spondyloarthropaties you can go to our section devoted to → Spondyloarthropathies.

Lyme Disease

Lyme disease is multisystemic infectious disease caused by the spirochaeta (type of bacterium) Borrelia burgdorferi and is transmitted to humans through the bite of infected blacklegged ticks. Typical symptoms of an early Lyme disease include fever, headache, fatigue, and a characteristic skin rash called erythema migrans. If left untreated, infection can spread to joints, the heart, and the nervous system. Lyme disease is diagnosed based on symptoms, physical findings (e.g., rash), and the possibility of exposure to infected ticks. Laboratory testing is helpful if used correctly and performed with validated methods.

Late disseminated Lyme disease (stage 3) occurs when the infection hasn’t been treated in stages 1 (early localised) and 2 (early disseminated). Stage 3 can occur months or years after the tick bite. This stage is characterized by: severe headaches, arthritis of one or more large joints, disturbances in heart rhythm, brain disorders (encephalopathy) involving memory, mood, and sleep, short-term memory loss, difficulty concentrating, mental fogginess, problems following conversations, numbness in the arms, legs, hands, or feet.

Diagnosis of late disseminatted Lyme disease is difficult. One should contact her/his doctor immediately if has any of above symptoms.

If you would like to read more about Lyme disease you can go to our section devoted to → Lyme Disease.

Myofascial Pain Syndrome

Myofascial pain syndrome is a chronic pain disorder. In this condition, pressure on sensitive points in your muscles (trigger points) causes pain in the muscle and sometimes in seemingly unrelated parts of your body. This is called referred pain.

This syndrome typically occurs after a muscle has been contracted repetitively. This can be caused by repetitive motions used in jobs or hobbies or by stress-related muscle tension.

While nearly everyone has experienced muscle tension pain, the discomfort associated with myofascial pain syndrome persists or worsens. Treatment options include physical therapy and trigger point injections. Pain medications and relaxation techniques also can help.

If you would like to read more about Myofascial Pain Syndrome you can go to our section devoted to → Myofascial Pain Syndrome.


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