Malnutrition is directly responsible for 300,000 deaths per year in children younger than 5 years in developing countries and contributes indirectly to more than half of all deaths in children worldwide. See the image below.
See 21 Hidden Clues to Diagnosing Nutritional Deficiencies, a Critical Images slideshow, to help identify clues to conditions associated with malnutrition.
Signs and symptoms
Clinical signs and symptoms of protein-energy malnutrition (PEM) include the following:
Poor weight gain
Slowing of linear growth
Behavioral changes: Irritability, apathy, decreased social responsiveness, anxiety, and attention deficits
The most common and clinically significant micronutrient deficiencies and their consequences include the following:
Iron: Fatigue, anemia, decreased cognitive function, headache, glossitis, and nail changes
Iodine: Goiter, developmental delay, and mental retardation
Vitamin D: Poor growth, rickets, and hypocalcemia
Vitamin A: Night blindness, xerophthalmia, poor growth, and hair changes
Folate - Glossitis, anemia (megaloblastic), and neural tube defects (in fetuses of women without folate supplementation)
Zinc: Anemia, dwarfism, hepatosplenomegaly, hyperpigmentation and hypogonadism, acrodermatitis enteropathica, diminished immune response, and poor wound healing
Physical findings that are associated with PEM include the following  :
Decreased subcutaneous tissue: Areas that are most affected are the legs, arms, buttocks, and face
Edema: Areas that are most affected are the distal extremities and anasarca (generalized edema)
Oral changes: Cheilosis, angular stomatitis, and papillar atrophy
Abdominal findings: Abdominal distention secondary to poor abdominal musculature and hepatomegaly secondary to fatty infiltration
Skin changes: Dry, peeling skin with raw, exposed areas; hyperpigmented plaques over areas of trauma
Nail changes: Fissured or ridged nails
Hair changes: Thin, sparse, brittle hair that is easily pulled out and that turns a dull brown or reddish color
See Clinical Presentation for more detail.
Initial diagnostic laboratory studies include the following:
Complete blood count
Stool specimens should be obtained if the child has a history of abnormal stools or stooling patterns or if the family uses an unreliable or questionable source of water.
The most helpful laboratory tests for assessing malnutrition in a child are hematologic and protein status studies.
Hematologic studies should include a complete blood count with red blood cell indices and a peripheral smear.
Measures of protein nutritional status include levels of the following:
Blood urea nitrogen
Additional laboratory studies
Other studies may focus on thyroid functions or sweat chloride tests, particularly if height velocity is abnormal.
Nutritional status studies
Practical nutritional assessment includes the following:
Complete history, including a detailed dietary history
Growth measurements, including weight and length/height; head circumference in children younger than 3 years
Complete physical examination
See Workup for more detail.
Children with chronic malnutrition may require caloric intakes of more than 120-150 kcal/kg/day to achieve appropriate weight gain. Most children with mild malnutrition respond to increased oral caloric intake and supplementation with vitamin, iron, and folate supplements. The requirement for increased protein is met typically by increasing the food intake.
In moderate to severe cases of malnutrition, enteral supplementation via tube feedings may be necessary.
The prevention of malnutrition in children starts with an emphasis on prenatal nutrition and good prenatal care. Promotion of breastfeeding is particularly crucial in developing countries where safe alternatives to human milk are unavailable. Health care providers should also counsel parents on the appropriate introduction of nutritious supplemental foods.
See Treatment for more detail.
The World Health Organization defines malnutrition as "the cellular imbalance between supply of nutrients and energy and the body's demand for them to ensure growth, maintenance, and specific functions."  Women and young children are the most adversely affected groups; one quarter to one half of women of child-bearing age in Africa and south Asia are underweight, which contributes to the number of low birth weight infants born annually. 
Malnutrition is globally the most important risk factor for illness and death, contributing to more than half of deaths in children worldwide; child malnutrition was associated with 54% of deaths in children in developing countries in 2001. [2, 3] Protein-energy malnutrition (PEM), first described in the 1920s, is observed most frequently in developing countries but has been described with increasing frequency in hospitalized and chronically ill children in the United States. 
The effects of changing environmental conditions in increasing malnutrition is multifactorial. Poor environmental conditions may increase insect and protozoal infections and also contribute to environmental deficiencies in micronutrients. Overpopulation, more commonly seen in developing countries, can reduce food production, leading to inadequate food intake or intake of foods of poor nutritional quality. Conversely, the effects of malnutrition on individuals can create and maintain poverty, which can further hamper economic and social development. 
Kwashiorkor and marasmus are 2 forms of PEM that have been described. The distinction between the 2 forms of PEM is based on the presence of edema (kwashiorkor) or absence of edema (marasmus). Marasmus involves inadequate intake of protein and calories, whereas a child with kwashiorkor has fair-to-normal calorie intake with inadequate protein intake. Although significant clinical differences between kwashiorkor and marasmus are noted, some studies suggest that marasmus represents an adaptation to starvation whereas kwashiorkor represents a dysadaptation to starvation. See the image below.
In addition to PEM, children may be affected by micronutrient deficiencies, which also have a detrimental effect on growth and development. The most common and clinically significant micronutrient deficiencies in children and childbearing women throughout the world include deficiencies of iron, iodine, zinc, and vitamin A and are estimated to affect as many as two billion people. Although fortification programs have helped diminish deficiencies of iodine and vitamin A in individuals in the United States, these deficiencies remain a significant cause of morbidity in developing countries, whereas deficiencies of vitamin C, B, and D have improved in recent years. Micronutrient deficiencies and protein and calorie deficiencies must be addressed for optimal growth and development to be attained in these individuals.
Malnutrition affects virtually every organ system. Dietary protein is needed to provide amino acids for synthesis of body proteins and other compounds that have various functional roles. Energy is essential for all biochemical and physiologic functions in the body. Furthermore, micronutrients are essential in many metabolic functions in the body as components and cofactors in enzymatic processes.
In addition to the impairment of physical growth and of cognitive and other physiologic functions, immune response changes occur early in the course of significant malnutrition in a child. These immune response changes correlate with poor outcomes and mimic the changes observed in children with acquired immune deficiency syndrome (AIDS). Loss of delayed hypersensitivity, fewer T lymphocytes, impaired lymphocyte response, impaired phagocytosis secondary to decreased complement and certain cytokines, and decreased secretory immunoglobulin A (IgA) are some changes that may occur. These immune changes predispose children to severe and chronic infections, most commonly, infectious diarrhea, which further compromises nutrition causing anorexia, decreased nutrient absorption, increased metabolic needs, and direct nutrient losses.
Early studies of malnourished children showed changes in the developing brain, including, a slowed rate of growth of the brain, lower brain weight, thinner cerebral cortex, decreased number of neurons, insufficient myelinization, and changes in the dendritic spines. More recently, neuroimaging studies have found severe alterations in the dendritic spine apparatus of cortical neurons in infants with severe protein-calorie malnutrition. These changes are similar to those described in patients with mental retardation of different causes. There have not been definite studies to show that these changes are causal rather than coincidental. 
Other pathologic changes include fatty degeneration of the liver and heart, atrophy of the small bowel, and decreased intravascular volume leading to secondary hyperaldosteronism.
Fewer than 1% of all children in the United States have chronic malnutrition. Incidence of malnutrition is less than 10%, even in the highest risk group (children in shelters for the homeless). Some studies indicate that poor growth secondary to inadequate nutrition occurs in as many as 10% of children in rural areas. Studies of hospitalized children suggest that as many as one fourth of patients had some form of acute PEM and 27% had chronic PEM.
The World Health Organization estimates that by the year 2015, the prevalence of malnutrition will have decreased to 17.6% globally, with 113.4 million children younger than 5 years affected as measured by low weight for age. The overwhelming majority of these children, 112.8 million, will live in developing countries with 70% of these children in Asia, particularly the southcentral region, and 26% in Africa. An additional 165 million (29.0%) children will have stunted length/height secondary to poor nutrition.
Currently, more than half of young children in South Asia have PEM, which is 6.5 times the prevalence in the western hemisphere. In sub-Saharan Africa, 30% of children have PEM. Despite marked improvements globally in the prevalence of malnutrition, rates of undernutrition and stunting have continued to rise in Africa, where rates of undernutrition and stunting have risen from 24% to 26.8% and 47.3% to 48%, respectively, since 1990, with the worst increases occurring in the eastern region of Africa. 
Malnutrition is directly responsible for 300,000 deaths per year in children younger than 5 years in developing countries and contributes indirectly to more than half the deaths in childhood worldwide.
The adverse effects of malnutrition include physical and developmental manifestations. Poor weight gain and slowing of linear growth occur. Impairment of immunologic functions in these children mimics those observed in children with AIDS, predisposing them to opportunistic and other typical childhood infections.
In developing countries, poor perinatal conditions account for 23% of deaths in children younger than five. Malnourished women are at high risk of giving birth to low birth weight infants. Many low birth weight infants (15-20% of all births worldwide)  face severe short-term and long-term health consequences, such as growth failure in infancy and childhood, which increases risk of morbidity and early death. 
Children who are chronically malnourished exhibit behavioral changes, including irritability, apathy and decreased social responsiveness, anxiety, and attention deficits. In addition, infants and young children who have malnutrition frequently demonstrate developmental delay in delayed achievement of motor skills, delayed mental development, and may have permanent cognitive deficits. The degree of delay and deficit depends on the severity and duration of nutritional compromise and the age at which malnutrition occurs. In general, nutritional insults at younger ages have worse outcomes. Dose-dependent relationships between impaired growth and poor school performance and decreased intellectual achievement have been shown. [3, 7, 8, 9]
Although death from malnutrition in the United States is rare, in developing countries, more than 50% of the 10 million deaths each year are either directly or indirectly secondary to malnutrition in children younger than 5 years. 
Children are most vulnerable to the effects of malnutrition in infancy and early childhood. Premature infants have special nutritional needs that are not met with traditional feeding recommendations; they require fortified human milk or specially designed preterm formula until later in infancy. Children are susceptible to malnutrition for differing reasons. During adolescence, self-imposed dietary restrictions contribute to the incidence of nutritional deficiencies.
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