Malnutrition Syndromes

Inadequate intake (the dominant mechanism worldwide)

• Food insecurity/poverty: the classic kwashiorkor stem is a toddler displaced from the breast by a new sibling and weaned onto a starch-based gruel — adequate calories, deficient protein.
• Anorexia of illness or aging: cancer cachexia, advanced heart failure, COPD, dementia, depression, and poor dentition all reduce intake; the Academy of Nutrition and Dietetics/ASPEN framework explicitly separates malnutrition from starvation, chronic disease, and acute inflammation.
• Psychiatric restriction: anorexia nervosa (DSM-5-TR) is the highest-yield non-tropical cause and the highest-risk substrate for refeeding syndrome.
• Iatrogenic: prolonged NPO status, repeated procedure holds, and unmonitored hospital diets.

Malabsorption/excess loss

• Small-bowel mucosal disease: celiac disease, Crohn disease, tropical sprue, giardiasis, HIV enteropathy.
• Maldigestion: chronic pancreatitis and cystic fibrosis (fat-soluble vitamins A, D, E, K); cholestasis impairs micelle formation.
• Anatomic loss: short bowel syndrome and bariatric surgery — Roux-en-Y predictably causes iron, B12, thiamine, and copper deficiency.
• Protein loss: protein-losing enteropathy and nephrotic syndrome produce hypoalbuminemic edema that mimics kwashiorkor.

Marasmus (Chronic Caloric Deficiency)

• Total energy deficit leads to catabolism of both fat and muscle stores for gluconeogenesis and ATP production
• Preferential preservation of visceral protein (organ function) at expense of somatic protein (skeletal muscle)
• Metabolic rate decreases; body shifts to ketotic state utilizing free fatty acids
• Relatively preserved albumin synthesis and immune function until late stages
• Results in wasting appearance with minimal edema

Kwashiorkor (Acute Protein Deficiency)

• Selective protein deficiency with relatively preserved caloric intake (classic scenario: weaning to carbohydrate-only diet)
• Impaired hepatic synthesis of albumin, clotting factors, and carrier proteins despite adequate caloric substrate
• Loss of oncotic pressure → third-spacing and dependent edema despite appearing "better nourished"
• Gut barrier dysfunction with increased intestinal permeability and bacterial translocation
• Immune system depletion occurs early with preserved fat stores
• Rapid clinical deterioration possible with infection or metabolic stress

Mixed PEM (Marasmic Kwashiorkor)

• Combination of chronic caloric deficiency with acute protein stress (infection, trauma, surgery)
• Most common form in hospitalized patients
• Worst prognosis due to combined organ dysfunction and immune compromise

Micronutrient-Specific Mechanisms

• Vitamin A deficiency: Loss of epithelial integrity, impaired night vision (reversible), corneal scarring (irreversible); requires retinol-binding protein (RBP) for transport
• Vitamin C deficiency (scurvy): Defective collagen cross-linking due to lack of hydroxylation cofactor
• Thiamine deficiency: Impaired pyruvate and α-ketoglutarate dehydrogenase → Wernicke-Korsakoff syndrome
• Niacin deficiency (pellagra): NAD+ depletion affecting oxidative metabolism
• Iron, B12, folate deficiency: Impaired hematopoiesis and DNA synthesis

Marasmus (Severe Wasting)

• Skeletal appearance with marked muscle atrophy, loss of subcutaneous fat, prominent ribs/vertebrae
• Loose, thin skin with loss of skin turgor ("skin and bones" appearance)
• Absence of significant edema (distinguishes from kwashiorkor)
• Bradycardia, hypotension, hypothermia (reduced metabolic rate)
• Alert mental status typically preserved until severe depletion
• Hair texture changes: sparse, fine, depigmented hair but not easily pluckable

Kwashiorkor (Protein Deficiency with Edema)

• Bilateral dependent edema (face, hands, feet, sacrum) despite wasting—pathognomonic finding
• Moon facies with relatively preserved cheeks masking underlying wasting
• Hepatomegaly with fatty infiltration and elevated transaminases
• Ascites may be present
• Flaky paint dermatitis: hyperpigmented, hyperkeratotic patches on pressure areas (elbows, knees) with desquamation
• Hair sign: hair easily pluckable, thin, reddish-brown discoloration, arranged in "flag sign" pattern (bands of depigmentation)
• Lethargy, irritability, apathy disproportionate to caloric deficit
• Rapid onset of symptoms over weeks to months

Overlapping/General Features (Both Syndromes)

• Immune dysfunction: increased susceptibility to infections (bacterial, fungal, TB)
• Diarrhea and malabsorption (villous atrophy, pancreatic insufficiency)
• Delayed wound healing; poor surgical outcomes
• Alopecia, brittle nails
• Hypothermia, cold intolerance
• Amenorrhea in females; decreased libido/erectile dysfunction
• Growth failure and developmental delay in children
• Anemia (multifactorial: iron, B12, folate, chronic disease)

Micronutrient Deficiency Features

• Vitamin A: Night blindness (early, reversible), Bitot's spots, corneal xerosis/ulceration (late, irreversible)
• Vitamin C (Scurvy): Bleeding gums, petechial hemorrhages, poor wound healing, bone pain (subperiosteal hemorrhage)
• Thiamine (Wernicke's): Ophthalmoplegia, ataxia, confusion (classic triad)
• Niacin (Pellagra): "4 Ds"—dermatitis, diarrhea, dementia, death; photosensitive rash on sun-exposed areas
• Vitamin D/Calcium: Rickets (children), osteomalacia (adults), tetany from hypocalcemia
• Iron: Microcytic anemia, koilonychia, dysphagia
• B12/Folate: Macrocytic anemia, neurologic symptoms (B12 only), glossitis

Clinical Assessment

• BMI <18.5 kg/m² indicates underweight; severe malnutrition typically BMI <16
• MUAC (Mid-Upper Arm Circumference) <23 cm in adults; gold standard in resource-limited settings
• Skinfold thickness measurements quantify fat stores (triceps, subscapular)
• Detailed dietary history: caloric intake, protein source, duration of symptoms

Laboratory Markers

• Serum albumin <3.5 g/dL (long half-life ~20 days; reflects chronic malnutrition); level of <2.5 g/dL indicates severe PEM
• Prealbumin/Transthyretin <20 mg/dL (short half-life ~2-3 days; better marker of acute protein status and treatment response)
• Total lymphocyte count <1,500 cells/μL indicates immune compromise
• Nitrogen balance: 24-hour urine urea nitrogen reflects protein catabolism
• Transferrin levels may be elevated with protein deficiency
• Serum amino acid ratios (Fischer ratio = BCAA/AAA; <3 indicates severe PEM)
• Specific micronutrient levels: retinol (vitamin A), thiamine, ascorbic acid, ferritin/iron studies, B12, folate

Diagnostic Scoring Systems

• SGA (Subjective Global Assessment): Combines history (weight loss, dietary intake, symptoms) with physical findings (muscle mass, fat stores, edema, ascites)
• GNRI (Geriatric Nutritional Risk Index) for elderly patients

Imaging and Other Studies

• DEXA scan: Assess bone mineral density in chronic malnutrition
• Chest X-ray: Rule out tuberculosis (high association with malnutrition)
• Abdominal ultrasound: Evaluate for fatty infiltration, hepatomegaly
• EKG: Look for prolonged QT, arrhythmias in severe cases

General Principles

• Address underlying cause (poverty, malabsorption, inadequate intake, hypermetabolism)
• Gradual refeeding to avoid refeeding syndrome (see Complications)
• Micronutrient supplementation concurrent with macronutrient repletion

Nutritional Repletion (First-Line)

• Oral feeding preferred when GI tract functional (most cost-effective, preserves gut barrier)
• High-calorie, high-protein foods; divided frequent meals (4-6 times daily)
• Typical caloric goal: 25-35 kcal/kg/day; protein

Emergencies of untreated malnutrition

• Hypoglycemia: depleted glycogen plus failed gluconeogenic substrate; signaled by lethargy, hypothermia, or seizure rather than adrenergic symptoms. WHO's stepwise management of severe acute malnutrition puts hypoglycemia and hypothermia first because they kill within hours.
• Sepsis with a blunted response: cytokine and neutrophil dysfunction mean no fever and no leukocytosis; hypothermia, hypoglycemia, or new lethargy is the presentation. WHO recommends routine broad-spectrum antibiotics in children with complicated severe acute malnutrition rather than waiting for signs.
• Cardiac atrophy and arrhythmia: myocardial mass falls with somatic protein; bradycardia, hypotension, and QTc prolongation predict torsades and sudden death.
• Keratomalacia: vitamin A deficiency progressing from Bitot spots to corneal ulceration — irreversible blindness within days, so give vitamin A empirically.

Complications of treatment

• Refeeding syndrome (the emergency examiners want): carbohydrate load → insulin surge → phosphate, potassium, and magnesium shift intracellularly while thiamine is consumed as a cofactor. Hypophosphatemia is the hallmark, typically falling within the first several days of feeding, causing ATP and 2,3-BPG depletion with rhabdomyolysis, respiratory muscle failure, heart failure, arrhythmia, seizures, and Wernicke encephalopathy. ASPEN's consensus recommendations advise identifying at-risk patients, giving thiamine before feeding, starting at a fraction of goal calories, and checking electrolytes before and serially after initiation.
• Fluid overload and heart failure: an atrophic myocardium plus a sodium load; watch for new edema or rising weight.
• Overfeeding: hyperglycemia, hypercapnia in ventilated patients, and hepatic steatosis.
• Route-specific harm: aspiration and tube misplacement with enteral feeding; catheter-related bloodstream infection, hyperglycemia, and parenteral nutrition–associated cholestasis with PN, which ASPEN reserves for a nonfunctional gut.
• Early iron repletion in severe acute malnutrition promotes oxidative stress and infection; WHO defers iron until the rehabilitation phase.

• Edema decides the syndrome: pitting edema plus flaky paint dermatosis, flag sign hair, and hepatomegaly in a well-appearing "chubby" child is kwashiorkor; skeletal wasting with normal albumin and no edema is marasmus. Marasmus with edema is a contradiction — that is marasmic kwashiorkor.
• The single best next step before feeding a chronically starved patient is thiamine plus measurement and repletion of phosphate, potassium, and magnesium, then cautious low-calorie initiation with serial electrolytes (ASPEN refeeding consensus). Feeding first and checking labs later is the trap answer.
• Falling phosphate 1–3 days after nutrition starts = refeeding syndrome, not sepsis. Weakness, delirium, hemolysis, and respiratory failure follow from ATP and 2,3-BPG depletion.
• Albumin is the classic distractor: it is a negative acute-phase reactant with a long half-life, so it tracks inflammation more than intake. Neither the Academy of Nutrition and Dietetics/ASPEN characteristics nor GLIM criteria use albumin or prealbumin as diagnostic criteria — diagnosis rests on weight loss, intake, body composition, and muscle mass.
• In severe acute malnutrition, absence of fever and leukocytosis does not exclude sepsis. WHO recommends empiric broad-spectrum antibiotics in complicated cases; hypothermia and hypoglycemia are the sepsis tell.
• The one association examiners repeat: vitamin A supplementation in children with measles or severe malnutrition reduces mortality and prevents keratomalacia (WHO). Bitot spots are the exam buzzword.
• Route matters: if the gut works, use it. ASPEN reserves parenteral nutrition for a nonfunctional GI tract; premature PN buys catheter sepsis and cholestasis.
• Rehydrate carefully in pediatric severe acute malnutrition: total body sodium is high despite low serum sodium, and IV fluids precipitate heart failure — WHO favors oral low-sodium, high-potassium rehydration solution unless the child is in shock.
• Post-bariatric stems: think thiamine early, then B12, iron, and copper — copper deficiency myelopathy mimics subacute combined degeneration.