 Fibromyalgia syndrome FMS and Chronic widespread pain CWP are two syndromes within a broader class known as functional somatic syndromes. Chronic widespread pain CWP is defined according to the American College of Rheumatology ACR, as pain both above and below the waist involving both sides of the body and lasting for at least 3 months. Fibromyalgia syndrome FMS, a subset of CWP, is a multisystem disease characterized by sleep disturbance, fatigue, headache, morning stiffness, paresthesias, and anxiety. 