Marasmus

n. weakening and wasting away of the body which occurs most often in children and infants (Latin)

Marasmus is a form of severe protein-energy malnutrition characterised by energy deficiency. Some other PEMs are kwashiorkor and cachexia (the most common one in the developed world).A child with marasmus looks emaciated and the body weight may reduce to less than 80% of the normal weight for that height.Marasmus occurrence increases prior to age 1 whereas Kwashiorkor occurrence increases after 18 months.
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Marasmus /ma·ras·mus/ a form of protein-energy malnutrition predominantly due to prolonged severe caloric deficit, chiefly occurring in the first [more]Marasmus - Community and Resources

Noun
1. extreme malnutrition and emaciation (especially in children); can result from inadequate intake of food or from malabsorption or metabolic disorders
(hypernym) malnutrition

(n.)
A wasting of flesh without fever or apparent disease; a kind of consumption; atrophy; phthisis.