Certain conditions are commonly associated with fibromyalgia, though their exact links to the condition are not well understood. The following conditions often appear along with fibromyalgia:

• Irritable bowel syndrome (IBS). Characterized by frequent abdominal pain, bloating and episodes of alternating constipation and diarrhea. More than half of all fibromyalgia patients suffer from this condition.
  
  
• Migraines. Many people with fibromyalgia also suffer migraines and other headaches. Researchers have found that a common link may be problems with a brain chemical called serotonin and adrenal hormones such as cortisol or adrenergic nerve fibers.
  
  
• Restless legs syndrome and periodic limb movement disorder. Characterized by uncontrollable contractions of the calf muscles and leg muscles that twitch, ache or feel like pins and needles. Many fibromyalgia patients experience this source of leg pain.
  
  
• Raynaud syndrome. Characterized by episodes of whitish and bluish discoloration of the fingers and toes, associated with tingling sensations, numbness or pain and the subsequent redness of the affected areas. It is usually triggered by cold temperatures and strong emotions. Researchers have reported that nearly half of all fibromyalgia patients suffer from this disorder.
  
  
• Urethral syndrome. Characterized by the often severe urge to urinate without an identifiable cause, such as infection. Often associated with urinary frequency and pelvic pain.
  
  
• TMJ disorder. Commonly associated with fibromyalgia. It is characterized by:
  
  
• • Jaw and facial pain or tenderness
    
    
  • Limited jaw movement
    
    
  • Clicking, snapping, or popping sounds while opening and closing the mouth
    
    
  • Pain within the facial or jaw muscles, as well as in or around the ear
    
    
  • Headaches
    
    
• Rheumatoid arthritis. A chronic disease primarily characterized by persistent inflammation of the joints, resulting in discomfort, pain, swelling and potential deformity of the affected joints. Fibromyalgia does not involve inflammation or deformity but may exist with rheumatoid arthritis. In fact, rheumatoid arthritis patients are more likely to develop fibromyalgia.
  
  
• Immune dysfunction. Fibromyalgia may cause a dysfunction with the immune system, making patients more susceptible to infections.

A great deal of controversy remains as to the relationship between fibromyalgia and certain similar disorders. Two disorders seem particularly linked to fibromyalgia, although physicians and researchers disagree on whether these links are substantiated:

• Chronic fatigue syndrome (CFS). A condition characterized by excessive fatigue that seriously impairs the patient’s ability to function. Many physicians believe that fibromyalgia and CFS may be different manifestations of the same underlying disorder. Both conditions share a large number of symptoms (e.g., headache, fatigue, pain) and similar physical abnormalities (e.g., reduced blood flow to key areas of the brain). Also, brain scans of fibromyalgia and CFS patients display very little difference. The most prominent difference lies in whether pain or fatigue is the most dominant symptom. Although fibromyalgia is the more common of the two, more than half of those diagnosed with fibromyalgia also fulfill the criteria for CFS.
  
  
• Myofascial pain syndrome (MPS). A chronic disorder characterized by pain and tenderness confined to a specific body region, such as the neck and shoulders. Many researchers have suggested that this may be a localized or regional form of fibromyalgia.