Fibromyalgia (FM) commonly occurs alongside rheumatological diseases as well as certain non-rheumatological disorders such as neurological, gastrointestinal, and psychological conditions, a review study found.

The study, “Comorbid fibromyalgia: a qualitative review of prevalence and importance,” was published in the European Journal of Pain.

Fibromyalgia — a disease characterized by chronic widespread body pain — is known to commonly occur with various rheumatological diseases. Although initially considered a unique condition, prevalent in 2-4% of the population, fibromyalgia is now increasingly recognized as coexisting with other rheumatological and non-rheumatological diseases.

Fibromyalgia that accompanies another disease is associated with a less favorable outcome, more severe symptoms, and impaired function. Therefore, if the condition goes undiagnosed in a patient who also has another disease, it can be detrimental because it requires treatment, and unrecognized fibromyalgia may be misinterpreted as poor control of the primary disease, affecting the management of both conditions.

Since there are few studies that have looked at the coexistence of fibromyalgia with other illnesses, with the exception of rheumatic diseases, researchers conducted a literature review to find evidence of the disorder occurring in different illnesses, and the effect it may have on the primary disease.

Fibromyalgia occurs in 20-30% of patients with various rheumatic conditions. In particular, one study showed that the disease was found in 21% of patients with rheumatoid arthritis, 37% of patients with systemic lupus erythematosis and 17% of patients with osteoarthritis.

Fibromyalgia is also reported to occur in patients with non-inflammatory musculoskeletal conditions, such as chronic spinal pain and chronic low back pain. It was also reported in 23-41% of patients with chronic disabling occupational musculoskeletal disorders.

There are four neurological conditions that have been reported to be associated with pain or fibromyalgia — multiple sclerosis (MS), post poliomyelitis syndrome, neuropathic pain, and Parkinson’s disease. However, no studies have assessed the outcome of the underlying disease when fibromyalgia is also present.

Fibromyalgia occurring with gastrointestinal diseases has mostly been reported for celiac disease and irritable bowel syndrome (IBS). However, studies that report the prevalence of the condition in IBS are conflicting, and there is no general consensus.

One study indicated that fibromyalgia is present in 23% of patients with heart failure, which, interestingly, is not a disease commonly associated with chronic pain.

Another study reported that 21% of patients with post-traumatic stress disorder also had fibromyalgia. Thus, the disease is not only present in physical disorders associated with pain but also mental conditions.

The authors believe that fibromyalgia may be an unidentified condition that occurs among many different diseases and may contribute to the overall burden of illness.

Because fibromyalgia coexisting with other disorders is associated with an overall less favorable health status in both rheumatic and non-rheumatic diseases, “physicians should be alert to the possibility of comorbid FM, and symptoms of FM should be specifically addressed,” the researchers said.