Protein-Energy Malnutrition

Basics

Description

  • The World Health Organization (WHO) defines malnutrition as “the cellular imbalance between the supply of nutrients and energy and the body’s demand for them to ensure growth, maintenance, and specific functions.”
  • A comprehensive definition of pediatric malnutrition has recently been proposed, 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.
  • This novel 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 (shorter than 3 months in duration) or chronic (longer than 3 months in duration).
  • The term “protein-energy malnutrition” (PEM) describes a general state of undernutrition and deficiency of multiple nutrients and energy.
  • There are three clinical presentations of severe PEM: kwashiorkor, marasmus, and marasmic kwashiorkor.
    • Kwashiorkor results from relative protein deficiency in the setting of adequate energy intake and is characterized by hypoproteinemia, pitting edema, varying degrees of wasting and/or stunting, dermatosis, and fatty infiltration of the liver.
    • Marasmus results from both energy and protein deficiency and is characterized by wasting, fatigue, and apathy.
    • Marasmic kwashiorkor is caused by acute or chronic protein deficiency and chronic energy deficit and is characterized by edema, wasting, stunting, and mild hepatomegaly.
    • The distinction between kwashiorkor and marasmus is frequently blurred, and many children present with features of both conditions.
  • Severe PEM covers a broad clinical spectrum ranging from frank kwashiorkor to severe marasmus when the body’s protein and energy requirements are not adequately met.
  • Cicely Williams introduced the name “kwashiorkor” in 1935 in a classic description of her observations of the Ga tribe on the Gold Coast of Africa (currently Ghana).
  • “Kwashiorkor” in the Ga language is translated as “the disease of the deposed child (deposed from the breast) when the next baby is born.”

Risk Factors

  • In developed nations, symptoms of kwashiorkor have been described in chronic malabsorptive conditions such as cystic fibrosis.
  • In the United States, a few cases of kwashiorkor unrelated to chronic illness have been described.
  • 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.

Epidemiology

  • Malnutrition underlies 55% of childhood mortality worldwide.
  • Kwashiorkor may occur at any age but is seen most frequently in children 1–3 years of age.
  • Kwashiorkor is seldom seen in the 1st year of life. It is usually seen in the 2nd year or beyond, when a toddler is fully weaned or only partially breastfed and may have a low intake of dietary protein.

Pathophysiology

  • 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, 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 the humoral immune system may be less protective.
    • Delayed wound healing may be seen owing to nutritional deficiencies.

Etiology

  • There are two principal theories regarding the etiology of kwashiorkor: the classical theory of protein deficiency and the newer theory of free radical damage.
  • Both theories emphasize different aspects of the environment: in the classical theory, nutrients, and in the free radical theory, oxidative stresses.
  • The classical theory of protein deficiency was supported by Williams’ original description of kwashiorkor developing in children who were weaned onto starchy gruels after being deposed from the breast and being cured by milk.
  • The free radical theory of kwashiorkor proposes that kwashiorkor results from an imbalance between the production of toxic free radicals and their safe disposal. Inadequate diet leads to a state of impaired antioxidant defense.
  • The free radical theory attempts to explain the entire spectrum of clinical findings in kwashiorkor by implicating a wide range of nutritional deficiencies, as well as environmental oxidative stressors (noxae):
    • Important noxae include infections and exogenous toxins such as aflatoxin and its metabolites.
    • Aflatoxin, from the fungus Aspergillus flavus, has been found in greater concentrations in the serum and urine of children with kwashiorkor than in controls.
    • There is a hierarchy of causes of PEM 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 PEM necessitates a multidisciplinary approach to its treatment and prevention.

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