Cachexia is a syndrome of metabolic dysfunction secondary to an underlying disease in which there is depleted skeletal muscle (sarcopenia) which may or may not be accompanied by an absolute loss of body fat.
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Terminology
Cancer cachexia is specifically used to refer to the cachexia associated with malignant disease. Similarly, cardiac cachexia is used for those with chronic heart disease who are cachectic.
Epidemiology
Associations
Cachexia is common with several chronic disease states including :
- cancer: commonest
- chronic cardiac failure
- chronic renal failure
- autoimmune diseases e.g. AIDS
Clinical presentation
In adults, cachexia is usually diagnosed when there is unequivocal loss of weight, whilst in children there is usually an impairment of normal growth 1. A loss of appetite (anorexia), insulin resistance and sarcopenia are often also present 1.
Cachexia is an entity which is distinct from other conditions such as starvation, malnutrition, malabsorptive states, hyperthyroidism, depression and loss of muscle bulk due to aging 1,3.
Pathology
Historically, it was thought that the cachexia associated with cancer was primarily due to a combination of anorexia and an elevated basal energy utilization 1. This is now deemed to be far too simplistic, not least because optimal dietetic interventions do not reverse the condition. The development of cachexia is complex and characterized by an interplay of metabolic, immunological and neurological factors 1.
Radiographic features
CT and MRI have been used to diagnose cachexia mainly by assessing for a depletion of absolute skeletal muscle mass, i.e. sarcopenia. The techniques are now highly accurate, and most measurements are felt to be within 1.5% of the true value 6.
History and etymology
Cachexia is derived from the Greek words κακος (kakos) meaning "bad" and εξις (hexis), a "bodily condition" or "state" 4,5.