The diagnosis of fibromyalgia is not easy, sometimes it takes years to diagnose it. This is because no abnormalities are seen in the physical examination of the person, the doctor cannot assess morning stiffness, extreme pain, chronic fatigue with the naked eye, because they are not quantifiable. But today, there are new biomarkers, such as the activity of the enzyme diamine oxidase (DAO), unfortunately, few doctors are up to date on this subject. To detect the activity of the DAO enzyme, diagnostic methods and new treatments have been developed. Rheumatological diseases caused by DAO deficiency