From Nicholas M, Vlaeyen JWS, Rief W, Barke A, Aziz Q, Benoliel R et al. The IASP classification of chronic pain for ICD-11 – chronic primary pain(external link) Pain 2019;160(1):28-37.
Fibromyalgia is classified under the ICD-11 as an example of Chronic Primary Pain, sub-type Widespread Pain. It is now considered to include nociplastic pain (see ISAP terminology(external link)) and central sensitization.
Chronic primary pain is defined as pain in one or more anatomical regions that persists or recurs for longer than 3 months is associated with significant emotional distress (eg, anxiety, anger, frustration, or depressed mood) and/or significant functional disability (interference in activities of daily life and participation in social roles), and the symptoms are not better accounted for by another diagnosis.
Specifically, it is chronic pain in one or more anatomical regions that persists or recurs for longer than 3 months and is associated with significant emotional distress and/or significant functional disability. The emotional distress can take many forms, such as demoralization, depressed mood, anxiety, anger, or frustration. Functional disability also covers a wide range of interference in daily life, such as difficulties working, sleeping, or taking part in social activities. In addition to these common features, the individual types of CPP have unique characteristics that distinguish one particular diagnosis from another.
Chronic widespread pain is diffuse musculoskeletal pain in at least 4 of 5 body regions and in at least 3 or more body quadrants (as defined by upper–lower/left–right side of the body) and axial skeleton (neck, back, chest, and abdomen). Chronic widespread pain is characterized by the core features of CPP, such as pain persisting for at least 3 months, and associated with significant emotional distress and/or functional disability. The diagnosis is appropriate if the pain is not directly attributable to a nociceptive process in these regions, and if there are features consistent with nociplastic pain, such as spontaneous or evoked pain in the affected regions, accompanied by allodynia and/or hyperalgesia and identified psychological and social contributors. Chronic widespread pain is often associated with increased medical comorbidity, including sleep disturbances, obesity, hypertension, and diabetes.
In order to explain the mechanisms of fibromyalgia or chronic primary pain to patients, you will need to learn about the modern neuroscientific understanding of pain and how it is produced in the body, especially how persistent pain can be created as a dysfunction of the pain system itself (see reading and websites below).
