Pathology · Year 2 · from Pathology
Case 3: Acute Gout - Crystal-Induced Inflammation
Patient Demographics
- Age: 58 years old
- Sex: Male
- Occupation: Business executive
Chief Complaint
"Sudden severe pain and swelling in my big toe that woke me from sleep"
History of Present Illness
A 58-year-old male presents to the emergency department at 3 AM with excruciating pain in his right first metatarsophalangeal (MTP) joint. The pain began suddenly 6 hours ago while he was sleeping and is the most severe joint pain he has ever experienced. He describes the area as extremely swollen, red, and warm. He cannot bear weight on the foot and even light touch of the bedsheet causes intense pain. He attended a business dinner last night where he consumed multiple glasses of wine and a large steak. Past medical history includes hypertension and hyperlipidemia. He takes hydrochlorothiazide and atorvastatin.
Physical Examination
- Vital Signs: BP 158/94 mmHg, HR 92 bpm, RR 16/min, Temp 37.8°C (100.0°F)
- General: Overweight male in obvious distress due to foot pain
- Right foot:
- First MTP joint: Severe erythema, swelling, warmth (all cardinal signs present)
- Exquisite tenderness to palpation (unable to tolerate examination)
- No skin breaks or signs of cellulitis tracking
- Other joints: No involvement
Diagnostic Workup
Laboratory Studies:
| Test | Result | Reference Range |
|---|---|---|
| WBC | 12,800/μL | 4,500-11,000/μL |
| Uric acid | 9.8 mg/dL | 3.5-7.2 mg/dL |
| BUN | 28 mg/dL | 7-20 mg/dL |
| Creatinine | 1.4 mg/dL | 0.7-1.3 mg/dL |
| CRP | 85 mg/L | <10 mg/L |
| ESR | 52 mm/hr | <20 mm/hr |
Joint Aspiration (Arthrocentesis):
| Parameter | Result |
|---|---|
| Appearance | Cloudy, yellow |
| WBC count | 45,000/μL |
| Differential | 85% neutrophils |
| Crystals | Needle-shaped, negatively birefringent |
| Gram stain | No organisms |
| Culture | No growth |
Imaging:
- X-ray of foot: Soft tissue swelling around first MTP; no erosions (first attack)
Pathology Correlation
This case demonstrates crystal-induced acute inflammation:
- Trigger Mechanism:
- Monosodium urate (MSU) crystals precipitate in joint when serum uric acid is elevated
- Crystals are phagocytosed by resident macrophages and neutrophils
- Crystal surface activates NLRP3 inflammasome
- Inflammatory Cascade:
- Inflammasome activation produces IL-1beta (key mediator)
- IL-1beta recruits neutrophils and amplifies inflammation
- Complement activation on crystal surface generates C5a (chemotactic)
- Neutrophils phagocytose crystals and release lysosomal enzymes
- Cardinal Signs:
- Rubor (redness): Vasodilation from histamine, prostaglandins
- Calor (heat): Increased blood flow and metabolic activity
- Tumor (swelling): Exudate from increased vascular permeability
- Dolor (pain): Bradykinin, prostaglandins stimulating nerve endings
- Functio laesa: Inability to bear weight
- Chemical Mediators:
- IL-1beta (central mediator; target of anakinra therapy)
- Prostaglandins (target of NSAIDs and colchicine)
- Complement fragments
- Neutrophil-derived enzymes and ROS
Clinical Image
Clinical photograph of acute gouty arthritis (podagra) affecting the first metatarsophalangeal joint. The classic findings of acute inflammation are evident: intense erythema (rubor), swelling (tumor), and the skin appears tense and shiny from edema. The patient reported severe pain (dolor) and heat (calor).
Image Source: Wikimedia Commons - "Gout" License: CC BY-SA 3.0 URL: https://commons.wikimedia.org/wiki/File:Gout_of_the_big_toe.jpg
Diagnosis
Acute Gouty Arthritis (Podagra) - First attack
Treatment
- Colchicine (inhibits neutrophil migration and inflammasome activation)
- NSAIDs (indomethacin) for acute inflammation
- Ice application and rest
- Discontinue hydrochlorothiazide (promotes hyperuricemia)
- Dietary counseling (reduce purine intake, alcohol)
- Plan to start urate-lowering therapy (allopurinol) after acute attack resolves
Teaching Points
- Crystal-induced inflammation demonstrates that acute inflammation can be triggered by non-infectious stimuli
- Negatively birefringent crystals (yellow when parallel to compensator) are diagnostic of gout
- The NLRP3 inflammasome is a key molecular sensor that activates IL-1beta production
- Colchicine works by inhibiting microtubule polymerization, blocking neutrophil chemotaxis
- Alcohol and purine-rich foods can precipitate attacks by increasing uric acid levels
- The intensity of gout pain illustrates the role of prostaglandins and bradykinin in inflammatory pain
- Thiazide diuretics reduce uric acid excretion and can precipitate gout