• Globally, the World Health Organization (WHO) identifies malnutrition in many forms, including undernutrition, inadequate intake of vitamins and minerals (micronutrients), and overweight/obesity. Undernutrition includes low weight-for-height (wasting), low height-for-age (stunting), and low weight-for-age (underweight). Obesity is addressed in a separate chapter.
  • In 2013, a comprehensive definition of pediatric malnutrition was put forth by the American Society for Parenteral and Enteral Nutrition (ASPEN) guidelines, which incorporates the chronicity, etiology, and severity of malnutrition, as well as the pathogenic mechanism of nutrient imbalance, association with inflammatory state, and impact on functional outcomes such as growth, development, neurocognition, lean body mass, muscle strength, and immune function. “Pediatric malnutrition (undernutrition) is defined as an imbalance between nutrient requirement and intake, resulting in cumulative deficits of energy, protein, or micronutrients that may negatively affect growth, development, and other relevant outcomes.”
  • This definition of pediatric malnutrition considers the etiology of energy, protein, and/or micronutrient imbalance as either “illness-related malnutrition” (secondary to disease/injury) or “non–illness-related malnutrition” (secondary to environmental/behavioral factors). Malnutrition may also be classified as either acute (<3 months in duration) or chronic (>3 months in duration).
  • In the United States, this issue has become very important in the setting of pediatric critical care, as children with malnutrition have increased mortality.
  • The older term “protein-energy malnutrition” describes a general state of undernutrition and deficiency of multiple nutrients and energy.
  • Malnutrition is much more common in areas that are resource poor with high levels of mortality age <5 years.
  • There are two clinical presentations of severe malnutrition: kwashiorkor and marasmus.
    • Kwashiorkor (edematous malnutrition) is characterized by hypoproteinemia, pitting edema, varying degrees of wasting and/or stunting, dermatosis, and fatty infiltration of the liver.
    • Marasmus is characterized by wasting, fatigue, and apathy and thought to be from deficiency of energy and protein, especially total calories.
    • The distinction between kwashiorkor and marasmus is frequently blurred, and many children present with features of both conditions as marasmic kwashiorkor.
  • Moderate to severe acute malnutrition is associated with 3 to 9 times higher mortality than well-nourished children.

Risk Factors

  • Undernutrition can be attributed to increased nutritional needs in a chronic disease setting or decreased intake in the setting of underresourced areas with endemic gastrointestinal (GI) and lower respiratory infections.
  • Lack of sanitation, poor hygiene, economic deprivation, and food insecurity are contributing factors. Availability of resources and design for allocation as determined by social, cultural, and political factors also affect undernutrition in less developed countries.
  • In developed nations, symptoms of kwashiorkor have been described in chronic malabsorptive conditions such as cystic fibrosis, but such cases have become increasingly rare as novel treatments for both underlying diseases and direct causes of malabsorption (e.g., pancreatic enzyme replacement) have become standard of care.
  • In the United States, a few cases of kwashiorkor unrelated to chronic illness have been described. This is usually due to severe neglect or previously undiagnosed chronic disease.
  • Consumption of a protein-deficient milk alternative, sugar water, or fruit juice can be due to poor caregiver knowledge about nutrition, a perceived milk or formula intolerance or adherence to food fads.
  • Consumption of a low-protein health food milk alternative, such as rice milk, secondary to a history of chronic eczema and perceived milk intolerance, has occurred in the United States.


  • Undernutrition underlies 45% of childhood mortality <5 years of age worldwide.
  • The WHO estimates that 52 million children <5 years old have wasting, of whom 17 million have severe acute malnutrition globally.
  • Moreover, 293 million children and 190 million of all preschoolers have iron deficiency anemia and vitamin A deficiency, respectively.
  • 2/3 of children with acute malnutrition live in South Asia, and 1/4 live in Africa.
  • The MAL-ED study follows eight global cohorts of children in Africa, Asia, and South America to identify environmental exposures including infection, nutrition, and socioeconomic factors and their impact on growth and development with several publications on nutritional status, stunting, environmental enteropathy, and diarrheal illness. As undernutrition is corrected, children and adolescents can have higher risk for obesity.


  • Temperature regulation is impaired, leading to hypothermia in a cold environment and hyperthermia in a hot environment.
  • Increase in total-body sodium and decrease in total-body potassium
  • Hypophosphatemia is associated with malnutrition and can result in high mortality, especially upon refeeding.
  • Protein synthesis is reduced, particularly albumin, transferrin, and apolipoprotein B. Decreased ability to transport fat leads to fatty infiltration of the liver.
  • Gluconeogenesis is reduced, which increases risk of hypoglycemia during infection.
  • Reduced cardiac output leads to low blood pressure, compromised tissue perfusion, and a reduction in renal blood flow and glomerular filtration rate.
  • Diminished inspiratory and expiratory pressures and vital capacity
  • Reduction of gastric and pancreatic secretions
  • Reduced intestinal motility
  • Intestinal mucosa atrophy resulting in malabsorption of carbohydrates, fats, and fat- and water-soluble vitamins
  • Low circulating insulin levels
  • Growth hormone secretion is increased, whereas somatomedin activity is reduced.
    • Glucagon, epinephrine, and cortisol levels are increased.
    • Serum T3 and T4 levels are reduced.
  • Immune system
    • T-cell immune function is diminished in malnutrition, thereby increasing susceptibility to infection.
    • Serum immunoglobulins are typically normal or increased, although enteral IgA is known to be decreased in experimental models of severe acute malnutrition.
    • Delayed wound healing may be seen owing to nutritional deficiencies.


  • Several theories have been proposed regarding the etiology of kwashiorkor with its characteristic edema, but more recent studies have suggested that protein deficiency and oxidant stress with free radical damage may be sequelae rather than causes.
  • Studies are suggesting a link between the gut microbiome and poor diet resulting in kwashiorkor. There is a hierarchy of causes of undernutrition operating at different levels and interacting with one another: from food scarcity, infection, malabsorption, and neglect; to poverty and social disadvantage; to drought, war, or civil disturbance.
  • The multiplicity of causes of undernutrition necessitates a multidisciplinary approach to its treatment and prevention.

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