Fibromyalgia - Conditions with Similar Symptoms

Some tests may be positive for one or more of these diseases. However, if the results are ambiguous or weak or if they have been treated successfully, fibromyalgia should not be ruled out if the patient still also meets the criteria for it.

Conditions That Usually Rule Out Fibromyalgia

Rheumatoid Arthritis and Other Autoimmune Diseases. Autoimmune diseases are conditions in which the person's immune system attacks the body's own tissues. Many autoimmune conditions resemble fibromyalgia. (Fibromyalgia, itself, may be an autoimmune disorder.) These diseases, like fibromyalgia, also occur more often in women than in men, and early symptoms are often muscle and joint pain and fatigue. The following are some autoimmune disorders that may be confused with fibromyalgia:

Rheumatoid arthritis is most apt to mimic fibromyalgia, and the similarities present diagnostic problems in both young people and adults. Symptoms include morning stiffness, fatigue, and tender points. Pressing such points, however, does not produce the intense pain that occurs with fibromyalgia, and abnormal laboratory tests can usually differentiate this disorder from fibromyalgia. Juvenile rheumatoid arthritis may coexist with fibromyalgia.

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Hashimoto's thyroiditis, a form of hypothyroidism marked by low levels of thyroid hormone, can cause widespread muscle aches, depression, and fatigue if left untreated. This condition is usually easily identifiable with thyroid hormone tests.

Hashimoto's disease (chronic thyroiditis)

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Systemic lupus erythematosus resembles fibromyalgia, although most patients with lupus also have a rash. Lupus can be diagnosed with a blood test.

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Multiple sclerosis has similar symptoms. There is no definitive test for diagnosing it. Magnetic resonance imaging scans, however, detect patches of injured tissue (lesions) in the brain that suggest MS.

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Sjogren's syndrome, a condition characterized by dry eyes and mouth, is sometimes mistaken for fibromyalgia.

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Autoimmune diseases generally evolve slowly. Even if a doctor determines that a patient is most likely to have fibromyalgia, he or she should keep track of any changes in symptoms over time in case one of these illnesses is actually present.

Lyme Disease. Early Lyme disease can usually be correctly diagnosed, but a delayed response or recurrence of this disorder may be mistaken for fibromyalgia. Some experts believe that between 15 - 50% of patients referred to clinics for Lyme disease actually have fibromyalgia. Late Lyme disease can usually (but not always) be ruled out using blood tests that identify the infectious organism that causes this tick-borne disease. If fibromyalgia patients are incorrectly diagnosed and treated for Lyme disease with prolonged courses of antibiotics, the drugs may have serious side effects.