- Fibromyalgia is characterized by widespread pain and tenderness, and has a significant familial component. The etiology of fibromyalgia remains unclear, but genetic factors seem to have a significant role, and are influenced by environmental factors. Research over the past two decades has demonstrated that genetic polymorphisms in the serotoninergic, dopaminergic and catecholaminergic systems of pain transmission and processing are involved in the etiology of fibromyalgia, but additional candidates continue to emerge. Fibromyalgia is thought to belong to the group of affective spectrum disorders, which include related psychiatric and medical disorders. As the concept of affective spectrum disorders continues to evolve, progress in the understanding of the genetic basis of related functional disorders, such as irritable bowel syndrome and post-traumatic-stress disorder, is aiding our understanding of the genetic basis of fibromyalgia.