Fibromyalgia is a widespread pain syndrome with several features including fatigue, irritable bowel syndrome, depression and cognitive dysfunction. It is considered to be a part of a family of related disorders known as affective spectrum disorders (ASD).

The ASDs have similar genetic associations and abnormalities. ASDs include other conditions such as:-

• attention-deficit/hyperactivity disorder
• bulimia nervosa
• generalized anxiety disorder
• major depressive disorder
• obsessive-compulsive disorder
• panic disorder
• posttraumatic stress disorder
• premenstrual dysphoric disorder
• social phobia
• irritable bowel syndrome
• migraine

Pathophysiology

These conditions thus share pathologies and manifestations in certain aspects. The pathophysiology of fibromyalgia include several aspects including:-

• neuroendocrine problems
• autonomic nervous system problems
• genetic factors
• psychosocial factors
• environmental stressors

Co-morbid factors

These factors are also included in the pathophysiology of the conditions that often co-exist with fibromyalgia. The co-morbid conditions like irritable bowel syndrome, temporomandibular disorder (TMD), and major depressive or anxiety disorders are also thus associated with persistent or recurrent pain and emotional distress.

Fibromyalgia also shares a common pathology with chronic inflammatory diseases and pain conditions like rheumatoid arthritis (RA), osteoarthritis, and systemic lupus erythematosus (SLE). These may co-exist with fibromyalgia complicating the course of the disease and making diagnosis and challenge.

Abnormal pain sensitivity

Patients with fibromyalgia have an increased sensitivity to pain sensations. They are more sensitive to heat and cold and to mechanical and ischemic (lack of blood flow) pressure. The pain evoked by these stimuli is perceived to be more severe in patients compared to normal persons.

The pathology behind this are the abnormal levels of serotonin and norepinephrine, which are key neurotransmitters or chemical messengers in the brain that inhibit pain within the brain and are integral parts of the endogenous pain inhibitory pathways.

Neuroendocrine problems

There is a considerable relation between psychological stress and fibromyalgia symptoms. There are problems in the functioning of the hypothalamic-pituitary-adrenal (HPA) axis.

Like other psychiatric conditions, fibromyalgia has been associated with the inability to suppress the stress hormone cortisol.

Problems in the autonomic nervous system

The functioning of the ANS is altered among patients with fibromyalgia. This contributes to enhanced pain and prevents effective stress management by the body.

There are decreases in blood pressure and decreased pain inhibition via reduced production of growth hormone (GH) and insulin-like growth factor (IGF-1).

Sleep problems

Patients with fibromyalgia suffer from sleep problems. Studies fail to show whether sleep problems give rise to fibromyalgia or vice versa. However, the association between the two conditions is clear.

Patients complain of insomnia, non-restorative or non-refreshing sleep, early morning awakening, and poor quality of sleep.

Genetic factors

Several candidate genes have been connected with fibromyalgia as well as its associated conditions.

The frequency of fibromyalgia among the first-degree relatives of those with fibromyalgia genetic makeup is around 6.4%. The median number of tender points among the first-degree relatives of the fibromyalgia genetic makeup is 17 out of maximum of 18.

Especially the serotonin transporter (5-HTT) gene is implicated in enhanced pain sensitivity.

Environmental factors

Environmental factors that may trigger fibromyalgia include mechanical/physical trauma or injury and psychosocial stress. Some of these include accidents and physical trauma, surgery, stress, emotional trauma, emotional, physical, or sexual abuse.