Origin of symptoms in patients with cachexia with special reference to weakness and shortness of breath.

Cachexia is a complication of many disorders. It is associated with an extremely poor prognosis and many symptoms. The wasting process affects particularly skeletal muscle causing extreme fatigue and weakness. In many underlying conditions associated with cachexia, the patient also suffers an often unexplained severe dyspnoea along with weakness, asthenia and exhaustion. There appears to be marked similarities in the cause of dyspnoea and fatigue between different cachectic conditions. Using the example of cardiac cachexia, this article reviews the evidence linking skeletal muscle reflex inputs to ventilatory control and exaggerated chemoreflex responses as candidates for the heightened perception of dyspnoea which cannot be explained by heart or lung dysfunction in many patients. Evidence is reviewed that similar processes may occur in other cachexias, especially those complicating cancer, AIDS, chronic liver disease, and chronic lung disease. Potential novel therapeutic strategies to combat these cachexia symptoms are reviewed.