Cachexia: common, deadly, with an urgent need for precise definition and new therapies.

Cachexia--sometimes also referred to as wasting disease, malnutrition, or hypercatabolism--has been described for centuries and has always raised ominous thoughts that "the end is near." The disease is encountered in many malignant and nonmalignant chronic, ultimately fatal, illnesses. Yet, although cachexia is a deadly syndrome, little is known about its pathophysiology, and the debate regarding its definition is ongoing. Thus, the data on epidemiology can be contested, but a few things are certain: Cachexia is associated with exceedingly high mortality once the syndrome has fully developed, irrespective of the definition we apply, and it is associated with weakness, weight loss, muscle wasting, and inflammation. It is not simply an ancillary event, and it may contribute to the death of the patient either through effects on neuroendocrine and immune defense mechanisms or through protein calorie malnutrition. The therapeutic standard of care for cachexia remains undefined to date, with a few exceptions. Among the recognized approaches, exogenous oral amino acid supplementation appears very promising. Further research efforts are needed and they are ongoing.