Classification of Malnutrition (10 marks)

Definition

I. By Etiology: Primary vs. Secondary

1. Gastrointestinal diseases (malabsorption syndromes, IBD, short bowel)
2. Chronic wasting diseases (advanced cancer, disseminated TB, AIDS - cachexia)
3. Acute critical illness (burns, sepsis - up to 80% rise in resting energy expenditure)

• Robbins & Kumar Basic Pathology

II. WHO Classification: Severe Acute Malnutrition (SAM)

• Weight-to-height ratio ≥3 standard deviations below the median growth standard, OR
• Visible severe wasting, OR
• Presence of nutritional edema

III. Waterlow Classification (Children)

IV. Clinical Syndromes of PEM in Children

1. Marasmus ("Nutritional Atrophy")

• Severe caloric deficiency (both protein and energy severely lacking)
• Somatic protein compartment (skeletal muscle) depleted predominantly
• Serum albumin normal or near-normal (visceral compartment spared)
• Features: profound growth retardation, gross emaciation, loss of subcutaneous fat, "matchstick" limbs with head appearing too large
• Low leptin stimulates the hypothalamic-pituitary-adrenal axis, causing high cortisol contributing to lipolysis
• Concurrent infections common due to T-cell mediated immune deficiency

2. Kwashiorkor ("Displaced Child")

• Protein deprivation relatively greater than caloric reduction; typically in children weaned onto a carbohydrate-only diet
• Visceral protein compartment (liver) depleted predominantly
• Hypoalbuminemia leads to generalized/dependent edema - hallmark feature
• Weight 60-80% of normal, but true weight loss is masked by fluid retention
• Features:
  • Peripheral and periorbital edema, ascites
  • Protuberant abdomen (weak abdominal muscles + intestinal distension + hepatomegaly)
  • Fatty liver (reduced synthesis of carrier protein of lipoproteins)
  • Skin lesions: alternating zones of hyperpigmentation, desquamation, and hypopigmentation
  • Hair changes: depigmentation, straightening, fine texture, easy pluckability
  • Apathy, listlessness, irritability when held
  • Serum albumin reduced (distinguishes from marasmus)

3. Nutritional Dwarfism (Stunting)

• Chronic inadequate nutrition causing impaired linear growth
• Weight for age reduced but weight for height may be near-normal
• Both somatic and visceral compartments affected, but less acutely

Note: These three syndromes overlap considerably in clinical practice. Marasmic-kwashiorkor is a mixed form with features of both.

V. Adult Malnutrition Classification

• Mild PEM: <5% unintentional weight loss over 6 months
• Moderate PEM: 5-10% weight loss
• Severe PEM: >10% weight loss

Effects of Malnutrition (10 marks)

1. Gastrointestinal Tract

• Villus atrophy with marked blunting of intestinal villi
• Loss of brush border hydrolases (disaccharidases, peptidases)
• Reduced gastric, pancreatic, and biliary secretions (volume and enzyme concentration)
• Malabsorption of carbohydrates, fats, fat-soluble and water-soluble vitamins
• Steatorrhea proportional to severity of PEM - creates a vicious cycle of further nutrient loss
• Bacterial overgrowth in upper small intestine
• Intestinal hypomotility and gas distension causing abdominal protuberance

2. Cardiovascular System

• Reduced myocardial mass (myofibrillar atrophy)
• Myocardial edema, patchy necrosis, chronic inflammatory cell infiltration
• Decreased stroke volume, cardiac output, and maximal work capacity
• Bradycardia and hypotension
• Cardiac failure can occur under conditions of increased metabolic demand

3. Immune System

• Impaired T-lymphocyte function (cell-mediated immunity most affected)
• Blunted polymorphonuclear leukocyte (PMN) function
• Reduced complement activity
• Variable impairment of B-lymphocyte antibody production
• Total lymphocyte count and delayed skin hypersensitivity are used diagnostically as markers of malnutrition
• Increased susceptibility to infections, which in turn worsen malnutrition (vicious cycle)

4. Liver

• Fatty liver (hepatic steatosis) in kwashiorkor - due to reduced synthesis of apolipoprotein, impairing VLDL export of fat from hepatocytes
• Hepatomegaly
• In severe/chronic malnutrition, impaired hepatic protein synthesis reduces albumin, coagulation factors, transport proteins

5. Skeletal Muscle and Somatic Protein

• Massive protein catabolism - urinary urea nitrogen losses rise to 2.5x basal levels at maximal stress
• Daily loss of up to 0.5 kg lean mass in severe illness
• AA efflux from skeletal muscle increases 2-6 fold in critically ill
• Progressive muscle wasting and weakness

6. Bone and Growth (Children)

• Stunted linear growth - impaired skeletal development
• Bone marrow suppression leads to anemia, leukopenia, lymphocytopenia
• Delayed epiphyseal closure and bone age
• In adults: osteopenia and increased fracture risk

7. Endocrine and Metabolic Effects

• Elevated cortisol (stress response) - promotes protein catabolism and lipolysis
• Low insulin, low IGF-1 - impairs anabolism
• Low leptin - further stimulates HPA axis
• Cytokine-mediated hypermetabolism: TNF-α, IL-1β, IL-6, IFN-γ all increase AA release from muscle, elevate acute-phase proteins, cause fever and anorexia
• Altered glucose homeostasis (hypoglycemia in severe SAM)

8. Skin and Appendages (especially Kwashiorkor)

• Flaky paint dermatosis - alternating zones of hyperpigmentation, desquamation, and hypopigmentation
• Hair changes: depigmentation ("flag sign" - alternating bands), straightening, fine texture, easy pluckability
• Poor wound healing
• Pressure ulcers

9. Neurological and Psychological Effects

• Apathy, listlessness, irritability (especially kwashiorkor)
• Impaired cognitive development and intellectual function in children
• Vitamin B deficiencies (thiamine, B12, folate) can cause peripheral neuropathy, Wernicke-Korsakoff syndrome
• Brain is relatively spared in direct protein-energy effects but indirect deficiencies cause damage

10. Renal and Other Effects

• Reduced glomerular filtration rate and tubular function
• Impaired wound healing and increased surgical risk
• Delayed recovery from illness
• Increased perioperative morbidity and mortality
• Secondary infections become the leading direct cause of death in malnourished children

Summary Table