One of the most important causes of ill health and death among children in the tropics. It is predominantly a deficiency disease due to a diet short of protein; there is also some evidence of a lack of essential fatty acids. It affects typically the small child weaned from the breast and not yet able to cope with an adult diet, or for whom an adequate amount of first-class protein is not available, and is mainly found in less well-developed countries.

The onset of the disease is characterised by loss of appetite, often with diarrhoea and weight loss. The child is flabby, the skin is dry, and the hair is depigmented, dry, sparse and brittle. At a later stage OEDEMA develops and the liver is often enlarged. In the early stages the condition responds rapidly to a diet containing adequate first-class protein, but in the later stages this must be supplemented by careful nursing, especially as the child is very prone to infection.