Chronic joint and limb pain is common and skeletal radiographs are normal [Sacheti et al., 1997]. Frequently it is difficult to establish the precise anatomical location of the pain.

Musculoskeletal pain is early in onset, chronic, and may be debilitating [Sacheti et al., 1997]. The anatomical distribution is wide and tender points can sometimes be elicited. A tender point is defined as an area that, when palpated with the thumb or 2 or 3 fingers will be painful at a pressure of 4 kg or less [Wolfe et al., 1990].