---

GOUT - Complete Notes for 1st Year MBBS

---

1. Definition

• Hyperuricemia (elevated uric acid in blood, >6.8 mg/dL)
• Deposition of monosodium urate (MSU) crystals in joints and soft tissues
• Recurrent attacks of acute arthritis, and in chronic cases, formation of tophi

Key rule: Hyperuricemia is necessary but not sufficient for gout. Gout is always preceded by hyperuricemia, but only ~10% of hyperuricemic individuals develop gout.

---

2. Biochemical Basis - Purine Degradation Pathway

• Hypoxanthine → Xanthine
• Xanthine → Uric acid

---

3. Causes of Hyperuricemia

A. Underexcretion (>90% of cases)

• Primary: Idiopathic defect in renal urate excretion (most common)
• Secondary:
  • Drugs: thiazide diuretics, low-dose aspirin, cyclosporine
  • Lead poisoning (saturnine gout)
  • Lactic acidosis (lactate competes with urate for excretion)
  • Chronic kidney disease

B. Overproduction (<10% of cases)

• Primary (idiopathic) - most common in this category
• Enzyme defects:
  • PRPP synthetase overactivity - increased purine synthesis
  • HGPRT (hypoxanthine-guanine phosphoribosyltransferase) deficiency - interrupts the purine salvage pathway; partial deficiency → gout; complete absence → Lesch-Nyhan syndrome (hyperuricemia + self-mutilation + neurologic features)
• Secondary overproduction:
  • Myeloproliferative disorders (high cell turnover)
  • Chemotherapy / tumor lysis syndrome
  • Von Gierke disease (glycogen storage disorder)

Risk factors for developing gout (from hyperuricemia):

• Age and duration of hyperuricemia (typically 20-30 years before gout appears)
• Male sex
• Diet rich in meat, shellfish, alcohol (especially beer)
• Diet poor in low-fat dairy (dairy products are protective)

---

4. Pathogenesis of Joint Inflammation

1. MSU crystals precipitate in the joint
2. Resident synovial macrophages phagocytose crystals → activates the NLRP3 inflammasome
3. Inflammasome activates caspase-1 → produces active IL-1β
4. IL-1β recruits neutrophils into the joint
5. Neutrophils also phagocytose crystals → lysosomal membranes rupture → hydrolytic enzymes released
6. Release of leukotrienes, free radicals, and proteases → acute arthritis
7. Attack typically remits spontaneously in days to weeks

• Formation of tophi (aggregates of MSU crystals + inflammatory tissue) in synovium and periarticular tissue
• Cartilage damage, joint destruction

---

5. Clinical Features (Four Stages)

---

6. Complications

• Urolithiasis - uric acid kidney stones
• Gouty nephropathy - urate crystal deposition in renal tubules/interstitium
• Joint destruction in chronic disease

---

7. Diagnosis

• Needle-shaped MSU crystals with negative birefringence (yellow when parallel to the polarizer axis)

---

8. Treatment

A. Acute Attack

B. Chronic Gout / Urate-Lowering Therapy (ULT)

Xanthine Oxidase Inhibitors (First-line ULT)

Uricosuric Agents (for underexcretors)

Recombinant Uricase

Important Note: Starting ULT can precipitate an acute attack (due to rapid shifts in serum urate). Co-prescribe low-dose colchicine or NSAIDs for at least 6 months when initiating ULT.

---

9. Colchicine - Detailed Pharmacology (High-Yield)

• Source: Plant alkaloid
• MOA: Binds tubulin → depolymerizes microtubules → blocks neutrophil migration + inhibits cell division (blocks mitotic spindle)
• NOT uricosuric, NOT analgesic
• Pharmacokinetics: Oral; absorbed from GI tract; metabolized by hepatic CYP3A4; enterohepatic recirculation
• Adverse effects: Nausea, vomiting, diarrhea, abdominal pain (most common); chronic use → myopathy, neutropenia, aplastic anemia, alopecia
• Interactions: CYP3A4 inhibitors (clarithromycin, itraconazole) and P-gp inhibitors (amiodarone, verapamil) increase toxicity
• Contraindicated in pregnancy

---

10. High-Yield Summary Table

---

• Robbins & Kumar Basic Pathology (Robbins Pathology), Chapter 19 - Bones, Joints and Soft Tissues
• Lippincott Illustrated Reviews: Biochemistry 8th ed, Chapter 22 - Purine Degradation
• Lippincott Illustrated Reviews: Pharmacology, Chapter 40 - Drugs for Gout

---

Glycogen Storage Diseases (Glycogenoses) - Complete Chart

---

Glycogen Pathway - Sites of Enzyme Defects

---

Hepatic vs Myopathic GSD - Visual Summary

---

Master GSD Chart

---

Three Pathophysiological Groups

---

High-Yield Memory Tricks

---

Key High-Yield Facts for Exams

• Most common GSD: Type I (Von Gierke)
• Only lysosomal GSD: Type II (Pompe) - enzyme is in lysosomes
• Only GSD with cardiomegaly as dominant feature: Pompe
• No lactate rise on exercise: Myopathic types (McArdle, Tarui) - block in glycolysis
• Limit dextrin accumulation: Type III (Cori) - debranching enzyme defect
• Inheritance: All types are autosomal recessive, except Type IX (X-linked phosphorylase kinase deficiency)
• Treatment available: Pompe disease - enzyme replacement therapy (alglucosidase alfa)
• GSD + gout + xanthomas: Von Gierke (Type I) - secondary hyperuricemia and hyperlipidemia
• GSD + hemolytic anemia: Type VII (Tarui) - PFK deficiency in RBCs too

---

Protein-Energy Malnutrition (PEM) - Biochemistry Notes for 1st Year MBBS

---

1. Definition

• Also called Protein-Energy Undernutrition (PEU)
• Most prevalent nutritional deficiency worldwide
• Predominantly affects children under 5 years in developing countries

---

2. Classification of PEM

A. By Clinical Form

B. Waterlow Classification (by Wasting and Stunting)

C. Gomez Classification (by Weight for Age)

---

3. Kwashiorkor - Detailed

Meaning

Cause

• Protein deprivation relatively greater than calorie deprivation
• Diet rich in carbohydrates but poor in protein (e.g., maize-based diet after weaning)
• Often precipitated by an acute infection or physiological stress on a chronically malnourished child

Biochemical Basis

1. Low protein intake → severely decreased synthesis of visceral proteins (albumin, transferrin, prealbumin)
2. ↓ Serum albumin → reduced plasma oncotic pressure → edema (fluid shifts from intravascular to interstitial compartment)
3. Adequate carbohydrate intake → insulin levels maintained → lipolysis and proteolysis suppressed
4. Fat cannot be mobilized from liver → fatty liver (hepatic steatosis)
5. Called "nonadapted malnutrition" because the body cannot properly adapt to protein lack

Clinical Features

• Bilateral pitting edema (legs, feet, face - "moon face")
• Protuberant abdomen (edema + hepatomegaly + weak abdominal muscles)
• Fatty liver / hepatomegaly
• Skin changes: "flaky paint" dermatosis, hyperpigmented patches, areas of peeling
• Hair changes: sparse, depigmented, easily pluckable, "flag sign" (bands of light/dark hair)
• Growth retardation (stunted)
• Apathy, lethargy; irritable when handled
• Depressed immunity → infections common

---

4. Marasmus - Detailed

Cause

• Calorie deprivation relatively greater than protein deprivation
• Both calories AND protein are deficient
• Usually in infants <1 year when breast milk is replaced with watery gruels

Biochemical Basis

1. ↓↓ Caloric intake → insulin levels fall markedly
2. ↓ Insulin → lipolysis activated → fat stores mobilized
3. Gluconeogenesis activated → muscle protein broken down for energy
4. Body adapts by reducing metabolic rate, mobilizing all energy stores
5. Called "adapted malnutrition" - the body has adapted to starvation

Clinical Features

• Severe wasting - "skin and bones," "old man face" (wrinkled face)
• No edema (distinguishes from kwashiorkor)
• Markedly depleted subcutaneous fat and muscle
• Weight <60% of expected
• Marked muscle wasting - "baggy pants" appearance (redundant skin over buttocks)
• Weakness, severe growth retardation
• Serum albumin relatively preserved (no edema)
• No fatty liver
• Alert, anxious expression (but weak)
• Thin, sparse hair (but not depigmented)

---

Clinical Images

---

5. Biochemical / Metabolic Changes in PEM

---

6. Why Edema in Kwashiorkor but NOT in Marasmus?

• In kwashiorkor: ↓ protein synthesis → ↓ serum albumin → ↓ plasma oncotic pressure → fluid shifts to interstitial space → pitting edema
• In marasmus: Protein intake is also reduced but the body adapts; edema does NOT develop because the reduction is proportionate and albumin is relatively preserved
• Key rule: Edema in PEM = think Kwashiorkor

---

7. Comparison: Why Does Kwashiorkor Develop Fatty Liver?

---

8. Assessment of PEM

---

9. Treatment Principles

Acute Phase (Stabilization)

1. Treat hypoglycemia, hypothermia, dehydration
2. Treat infections (broad-spectrum antibiotics)
3. Correct electrolyte imbalances (K⁺, Mg²⁺, phosphate)
4. Start feeding cautiously (avoid refeeding syndrome)

Refeeding syndrome warning: Rapid refeeding of carbohydrates → insulin surge → drives phosphate, K⁺, Mg²⁺ intracellularly → hypophosphatemia (most dangerous), hypokalemia, hypomagnesemia → cardiac arrhythmias, respiratory failure. Milk is given as it is rich in phosphate.

Rehabilitation Phase

• Gradually increase protein and calorie intake
• High-protein, high-calorie diet (milk, eggs, pulses)
• Treat micronutrient deficiencies (Vitamin A, zinc, iron)
• Treat underlying infections and parasites

Community Level Prevention (Park's)

1. Promote breastfeeding
2. Develop low-cost weaning foods
3. Nutrition education
4. Immunization (prevents infections that precipitate PEM)
5. Family planning (birth spacing)
6. Food fortification

---

10. High-Yield Summary Table

---

11. Mnemonics

• Lippincott Illustrated Reviews: Biochemistry 8th Ed, Chapter 27
• Park's Textbook of Preventive & Social Medicine
• Sleisenger & Fordtran's Gastrointestinal & Liver Disease