Fibromyalgia Explained to Patients. A Letter to Patients Based on Scientific Evidence

This document addresses fibromyalgia from a scientific and clinical perspective, in language intended to be accessible to patients and their families. It examines: the diagnostic criteria of the American College of Rheumatology (2016); the WHO classification of fibromyalgia as a chronic primary pain condition and its explicitly biopsychosocial nature in the ICD-11; the concept of nociplastic pain introduced by the International Association for the Study of Pain in 2017; the pathophysiological mechanisms, including central sensitization, neuroinflammation, and dysregulation of the hypothalamic–pituitary–adrenal axis; the role of psychology in modulating the upstream processes that sustain chronic pain; the evidence on the efficacy of pharmacological and non-pharmacological treatments; and data on long-term prognosis. The aim is to provide accurate, evidence-based information, countering myths and misinformation, and to offer patients concrete tools to understand and manage their condition.