Final answer:
The distinctive feature of cachexia in pediatric oncology patients is the 4) progressive wasting of both lean tissue and body fat, which is a result of the underlying illness and comes with muscle atrophy and a significant loss of appetite.
Step-by-step explanation:
The characteristic of cachexia in pediatric oncology patients is progressive wasting of lean tissue and body fat. Cachexia is a complex syndrome associated with an underlying illness such as cancer that causes a severe loss of weight, muscle atrophy, fatigue, weakness, and a significant loss of appetite.
It involves not only gradual weight loss but also atrophy, where there is a decrease in muscle mass. Unlike simple weight loss, cachexia is characterized by depletion of both lean body mass and adipose tissue. Children may experience undernutrition, which becomes particularly severe, causing wasting and potentially stunting, with long-lasting effects on growth and development.