Protein-energy malnutrition (PEM) results when the body's needs for protein and energy fuels are not satisfied by the diet. It is accompanied by deficiency of several micronutrients, and its clinical characteristics are conditioned by the relative severity of energy, protein, and micronutrient deficit, the duration and cause of the deficiencies, the age of the host, and the association with infectious diseases. Severe PEM can become manifest as marasmus, a nonedematous syndrome characterized by gradual emaciation associated with near starvation and predominant energy deficit, or as kwashiorkor, a syndrome characterized by bipedal edema that progresses rapidly, associated with predominant protein deficiency and varying degrees of energy deficit. Marasmic kwashiorkor combines edema and emaciation associated with chronic energy deficiency and chronic or acute protein deficit. Milder forms of the disease result in weight loss, growth retardation, and several forms of functional impairment.



The origin of PEM can beprimary, when it is the result of inadequate food intake, orsecondary, when it is the result of other diseases that lead to low food ingestion, inadequate nutrient absorption or utilization, increased nutritional requirements, and/or increased nutrient losses. Its onset can be relatively fast, as in starvation resulting from abrupt withholding of food, or gradual. This chapter discusses primary PEM of a relatively gradual onset, in which the metabolic alterations and clinical characteristics of protein and/or energy deficits predominate. PEM secondary to other diseases and the metabolic and clinical manifestations of starvation and of specific vitamin and mineral deficiencies are described in other chapters.It has long been recognized that inadequate food intake produces weight loss and growth retardation and, when severe and prolonged, leads to body wasting and emaciation. It has taken longer to understand the nature of the edematous forms of PEM, partly because they could be found among children who were not starving.PEM is the most important nutritional disease in developing countries because of its high prevalence and relationship with child mortality rates, impaired physical growth, and inadequate social and economic development. Most deaths of children 6 to 59 months old in developing countries are attributable to the potentiating effects of moderate and severe malnutrition on infections. Malnutrition is especially associated with increased risk of death from diarrhea and acute lower respiratory infections, and nutritional interventions reduce the risk. Conversely, infections are a major factor in the etiology of PEM as a result of increased nutrient demands, greater nutrient losses, and disruption of metabolic equilibrium. In industrialized countries, primary PEM is seen mainly among young children of the lower socioeconomic groups, elderly persons who live alone, and adults addicted to alcohol and drugs. Some cases of kwashiorkor have been reported in association with diet faddism and nutritional ignorance.Prevalence of stunting, an indicator of child malnutrition, has decreased gradually in the last 25 years. Yet, there are still about 800 million undernourished people in the world, and child malnutrition remains a major public health problem in developing countries; in some of these countries, severe malnutrition is the most common reason for pediatric hospitalization. Around 27% of the children younger than the age of 5 years in the developing world are underweight, 32% are stunted, and 10% are wasted, based on a deficit of more than 2 standard deviations below the World Health Organization (WHO)/US National Center for Health Statistics reference values for weight for age, height for age and weight for height, respectively. This prevalence ranges from 8% underweight, 16% stunted, and 3% wasted in Latin America and CEE/CIS/ Baltic states to 46% underweight, 44% stunted, and 15% wasted in South Asia.