Fibromyalgia is characterized by widespread muscle pain, fatigue, and weakness. The abnormalities associated with this condition may be classified as:-
Abnormalities within the muscles
Studies have shown definite metabolic abnormalities within the muscles that can be associated with the condition.
When examined under the light microscope as well as the electron microscope abnormalities of the membranes, mitochondria, and fiber type have been seen.
These are structural abnormalities that may co-exist with biochemical abnormalities, metabolic problems like altered energy production leading to dysfunction of the muscles in fibromyalgia.
Functional problems of muscles are assessed most directly by strength and endurance tests. These may be severely affected by pain and psychological factors.
The muscle problems are associated with neurologic findings and disturbances in the hypothalamic-pituitary-adrenal axis.
Within the muscles the metabolic factors may be altered because of the intrinsic changes within the muscle tissue or extrinsic influences from neurological or endocrine (hormonal) factors.
Measuring metabolic abnormalities of the muscles
The metabolic abnormalities of the muscles are measured using traditional biopsy techniques as well as nuclear magnetic resonance spectroscopy (P-31 MRS).
Biopsy studies looked at the metabolism of the energy currency of the muscles or ATP, creatine phosphate (this is the most important store of high energy phosphate in the cell), ADP, AMP, pyruvate and glycogen.
Results show that levels of creatinine phosphate and ATP are significantly lower (21% and 17%, respectively) in fibromyalgic muscle. In addition the synthesis of creatinine phosphate is defective. Thus energy metabolism in the fibromyalgia muscle is abnormal.
Using the P-31 MRS studies the absolute values of energy compounds, changes in metabolism at rest and during exercise and the muscle pH can be measured.
These studies show that resting levels of ATP are 15% lower in fibromyalgia patients than healthy individuals and during exercise the creatinine phosphate and ATP levels are also significantly lower by 15% each.
During exercise there is an increase in metabolic breakdown products of ATP indicating abnormal ATP metabolism and breaking of the cell membranes. Both these features are associated with muscle disease.
On assessment of blood, results showed that lactate production, leucocyte-NAD, catalase, lacticodehydrogenase muscular isoenzymes, taurine, glutathione, values decreased and pyruvate or acyl carnitine/free carnitine ratio and erythrocyte-transketolase activity coefficient, values were increased in patients with fibromyalgia.
The mitochondrial respiratory chain was unchanged. There were reduced nitric oxide and antioxidant defences as detected from these parameters.
Reviewed by April Cashin-Garbutt, BA Hons (Cantab)