Over the years, studies have revealed that a pain processing abnormality as an explanation for the pain fibromyalgia patients experience. Several observations have been made, noting elevated Substance P in cerebrospinal fluid, and increased Glutamate activity. These observations are not a cause, but rather a symptom of a much bigger picture. Some morphological studies have been done showing ragged red fibers in skeletal muscles, in addition to atrophy of type II fibers. Surprisingly few studies of this nature have been done, considering that performing a muscle biopsy with a special needle is relatively simple, and does not require any incision.
The pain processing abnormalities in Fibromyalgia are not unique. It has become clearly established that Interleukin-1 Beta is an inducer of Cyclooxygenase-2 mediated inflammatory pain hypersensitivity, which in turn up-regulates substance P and Glutamate transport. Muscle pain in influenza bears a striking similarity to Fibromyalgia pain, although it resolves itself once the virus is cleared from the body. In Fibromyalgia, likely the XMRV virus plays a pivotal role.