# Clinical Cases: Crystal Arthropathies

## Case 1: Acute Gouty Arthritis (Podagra)

### Patient Presentation
**Demographics:** 54-year-old man

**Chief Complaint:** "I woke up at 3 AM with the worst pain I've ever had in my big toe."

**History of Present Illness:**
The patient describes sudden onset of severe pain in his right first metatarsophalangeal (MTP) joint that awakened him from sleep approximately 8 hours ago. The pain reached maximum intensity within hours and is so severe that even the weight of the bedsheet is unbearable. He notes the joint is swollen, red, and hot. He had a large steak dinner with several beers last night while watching a sports game. He has had one similar, less severe episode affecting the same toe about 18 months ago that resolved spontaneously over a week without medical attention.

**Past Medical History:**
- Hypertension
- Hyperlipidemia
- Obesity
- Chronic kidney disease stage 2 (eGFR 72 mL/min)

**Medications:**
- Hydrochlorothiazide 25 mg daily
- Lisinopril 20 mg daily
- Atorvastatin 40 mg daily

**Social History:**
- Sales manager
- Drinks 2-3 beers daily, more on weekends
- Non-smoker

**Family History:**
- Father had "gout"

### Physical Examination
- **Vital Signs:** BP 148/92 mmHg, HR 88 bpm, Temp 37.9C, BMI 32 kg/m2
- **General:** In significant discomfort, holding right foot elevated
- **Right Foot:**
  - First MTP joint: markedly swollen, erythematous, warm
  - Exquisite tenderness - cannot tolerate light touch
  - Overlying skin appears shiny and tense
  - Appears cellulitic
- **Other joints:** No swelling or tenderness
- **Skin:** No tophi identified

### Workup and Results

**Laboratory Studies:**
| Test | Result | Reference Range |
|------|--------|-----------------|
| Serum Uric Acid | 7.2 mg/dL | 3.5-7.2 mg/dL (upper normal during attack) |
| WBC | 12,400/mm3 | 4,500-11,000/mm3 |
| Creatinine | 1.3 mg/dL | 0.7-1.3 mg/dL |
| eGFR | 68 mL/min | >90 mL/min |
| ESR | 58 mm/hr | 0-15 mm/hr |

**Synovial Fluid Analysis (First MTP aspiration):**
| Test | Result | Interpretation |
|------|--------|----------------|
| Appearance | Cloudy, yellow | Inflammatory |
| WBC | 42,000/mm3 | Inflammatory (>2,000) |
| PMN | 88% | Neutrophil predominant |
| Crystals | Needle-shaped, negatively birefringent | Monosodium urate (diagnostic) |
| Gram Stain | No organisms | Excludes septic arthritis |

**Imaging:**
- **Foot X-ray:** Soft tissue swelling at first MTP joint, no erosions or tophi

### Clinical Image

![Acute gout podagra](case_01_image.jpg)

*Clinical photograph demonstrating acute gouty arthritis of the first metatarsophalangeal joint (podagra) with marked erythema, swelling, and shiny, tense skin overlying the joint. Source: [Wikimedia Commons](https://commons.wikimedia.org/wiki/File:Gout2010.JPG), CC BY-SA 3.0.*

### Diagnosis
**Acute Gouty Arthritis (Podagra) - Crystal-Proven**

**Diagnostic Certainty:**
- Monosodium urate crystals identified on polarized microscopy (gold standard)
- Characteristic clinical presentation (rapid onset, severe pain, first MTP involvement)
- Risk factors present (male, obesity, hypertension, CKD, thiazide diuretic, alcohol, dietary triggers)

### Treatment Plan

**Acute Attack Management:**
1. **Colchicine (low-dose regimen):** 1.2 mg initially, then 0.6 mg one hour later (total 1.8 mg day 1), then 0.6 mg BID until attack resolves
   - Chosen over NSAIDs due to CKD
2. **Prednisone:** 30 mg daily x 5 days as alternative if colchicine insufficient
3. **Ice, elevation, rest**

**Medication Review:**
- Discontinue hydrochlorothiazide (contributes to hyperuricemia)
- Switch to losartan for hypertension (has mild uricosuric effect)

**Patient Education:**
- Dietary counseling: limit red meat, organ meats, shellfish; reduce alcohol especially beer
- Increase water intake
- Weight loss counseling

**Urate-Lowering Therapy Discussion:**
- Indication: recurrent attacks (this is his second)
- Plan to start allopurinol 2-4 weeks after acute attack resolves
- Will require flare prophylaxis with colchicine when initiating ULT
- Target serum uric acid <6 mg/dL

**Follow-up:**
- Recheck uric acid 2-4 weeks after attack (when not acutely inflamed)
- Return if symptoms not improving or worsening

### Teaching Points
1. **Serum uric acid during attacks:** May be normal or even low due to uricosuric effect of inflammation; does not exclude gout
2. **Crystal identification is definitive:** Needle-shaped negatively birefringent (yellow when parallel to compensator) MSU crystals confirm diagnosis
3. **Colchicine low-dose regimen:** 1.2 mg + 0.6 mg is as effective as high-dose with far less GI toxicity
4. **Diuretics and gout:** Thiazides and loop diuretics increase uric acid and gout risk
5. **Urate-lowering therapy:** Don't start during acute attack (can prolong); start after resolution with prophylactic colchicine to prevent mobilization flares

---

## Case 2: Chronic Tophaceous Gout

### Patient Presentation
**Demographics:** 68-year-old man

**Chief Complaint:** "I have painful bumps on my fingers and my joints hurt all the time."

**History of Present Illness:**
The patient has a 20-year history of gout with numerous acute flares, initially affecting his feet but now involving multiple joints. He has been non-compliant with urate-lowering therapy, stopping and starting allopurinol multiple times due to flares when initiating treatment. Over the past 5 years, he has developed visible lumps on his fingers, elbows, and ears. He now experiences constant low-grade joint pain with superimposed acute flares every few weeks. His most recent flare began 4 days ago affecting his right wrist.

**Past Medical History:**
- Gout for 20 years
- Chronic kidney disease stage 3b (eGFR 38 mL/min)
- Hypertension
- Type 2 diabetes mellitus
- Congestive heart failure (EF 40%)

**Medications:**
- Allopurinol 100 mg daily (restarted 1 month ago)
- Furosemide 40 mg daily
- Carvedilol 12.5 mg twice daily
- Lisinopril 20 mg daily
- Metformin 500 mg twice daily
- Aspirin 81 mg daily

### Physical Examination
- **Vital Signs:** BP 142/88 mmHg, HR 72 bpm, BMI 30 kg/m2
- **Hands:**
  - Multiple firm, irregular nodules (tophi) over DIP joints, PIP joints
  - White chalky material visible through skin at some sites
  - Right wrist: actively inflamed with warmth, swelling, tenderness
  - Chronic deformity of multiple finger joints
- **Elbows:** Large olecranon tophi bilaterally
- **Ears:** Tophi visible on helices bilaterally
- **Feet:** Chronic deformity of first MTP joints with overlying tophi

### Workup and Results

**Laboratory Studies:**
| Test | Result | Reference Range |
|------|--------|-----------------|
| Serum Uric Acid | 10.8 mg/dL | 3.5-7.2 mg/dL (elevated) |
| Creatinine | 1.9 mg/dL | 0.7-1.3 mg/dL |
| eGFR | 38 mL/min | >90 mL/min |
| ESR | 48 mm/hr | 0-15 mm/hr |

**Imaging:**
- **Hand radiographs:**
  - Asymmetric soft tissue masses (tophi)
  - Punched-out erosions with overhanging edges ("rat bite" erosions, Martel sign)
  - Relative preservation of joint space in early erosive areas
  - No osteopenia
- **Dual-energy CT:** Extensive urate deposition in hands, wrists, feet, elbows

### Clinical Image

![Uric acid crystals](case_02_image.jpg)

*Polarized light microscopy of synovial fluid showing needle-shaped, negatively birefringent monosodium urate crystals within neutrophils, diagnostic of gout. The crystals appear yellow when parallel to the axis of the red compensator. Source: [Wikimedia Commons](https://commons.wikimedia.org/wiki/File:Gout_Uric_Acid_Crystals_-_Aspirate.jpg), Public Domain.*

### Diagnosis
**Chronic Tophaceous Gout with Acute Flare**

**Features:**
- Visible tophi at multiple sites
- Chronic gouty arthropathy with erosions
- Ongoing hyperuricemia despite low-dose allopurinol
- Active flare superimposed on chronic disease
- Multiple comorbidities complicating treatment

### Treatment Plan

**Acute Flare Management:**
1. **Prednisone:** 30 mg daily for 5 days then stop (NSAIDs contraindicated due to CKD and heart failure; colchicine requires dose reduction and caution)
2. **Consider intra-articular injection** of wrist with triamcinolone if accessible

**Urate-Lowering Therapy Optimization:**
1. **Continue allopurinol and titrate:** Currently 100 mg; increase gradually by 100 mg every 2-4 weeks
   - Target: Serum uric acid <5 mg/dL (lower target for tophaceous gout)
   - May need doses up to 300-400 mg despite CKD (dose can exceed GFR-based limits if tolerated and monitored)
2. **Prophylaxis:** Low-dose colchicine 0.3 mg daily (reduced dose for CKD) during ULT titration

**Monitoring:**
- Serum uric acid monthly during titration
- Renal function, CBC every 2-4 weeks during allopurinol titration
- Watch for hypersensitivity reaction signs

**If Refractory:**
- Consider pegloticase if fails conventional ULT (requires infusion center, risk of immunogenicity)
- Urology referral for nephrolithiasis assessment

### Teaching Points
1. **Tophaceous gout:** Develops after years of inadequately controlled hyperuricemia; represents massive urate burden
2. **Target uric acid <5 mg/dL:** Lower target for tophaceous gout to promote tophus dissolution; below saturation point allows crystals to dissolve
3. **Allopurinol dosing in CKD:** Can exceed traditional GFR-based dose limits with careful monitoring; achieving target uric acid more important than arbitrary dose ceiling
4. **Radiographic findings:** "Punched-out" erosions with overhanging edges (Martel sign), preserved joint space initially, asymmetric soft tissue masses - classic for gout
5. **Treatment challenges:** Multiple comorbidities (CKD, CHF) limit NSAID use; colchicine requires dose adjustment; glucocorticoids often necessary

---

## Case 3: Calcium Pyrophosphate Deposition Disease (Pseudogout)

### Patient Presentation
**Demographics:** 75-year-old woman

**Chief Complaint:** "My right knee suddenly became swollen and painful after my hip surgery last week."

**History of Present Illness:**
The patient underwent right total hip arthroplasty 8 days ago for osteoarthritis. She was recovering well until 2 days ago when she developed acute pain and swelling in her right knee without any trauma. The knee became increasingly swollen, warm, and painful, making it difficult to participate in physical therapy. She had a similar episode affecting her left knee 3 years ago that was diagnosed as "pseudogout."

**Past Medical History:**
- Osteoarthritis (hips, knees)
- Hypothyroidism
- Type 2 diabetes mellitus
- Prior episode of "pseudogout" left knee 3 years ago

**Medications:**
- Levothyroxine 75 mcg daily
- Metformin 1000 mg twice daily
- Enoxaparin 40 mg subcutaneously daily (DVT prophylaxis post-surgery)
- Oxycodone/acetaminophen 5/325 mg PRN pain

**Surgical History:**
- Right total hip arthroplasty 8 days ago

### Physical Examination
- **Vital Signs:** BP 138/82 mmHg, HR 84 bpm, Temp 37.6C
- **General:** Elderly woman, uncomfortable but not toxic
- **Right Knee:**
  - Large tense effusion
  - Warmth and erythema
  - Moderate tenderness
  - Limited range of motion due to pain and swelling
- **Right Hip:** Surgical incision healing well, no signs of infection
- **Left Knee:** Mild crepitus, no effusion

### Workup and Results

**Laboratory Studies:**
| Test | Result | Reference Range |
|------|--------|-----------------|
| WBC | 10,800/mm3 | 4,500-11,000/mm3 |
| ESR | 62 mm/hr | 0-30 mm/hr (elevated post-surgery) |
| CRP | 4.8 mg/dL | <0.5 mg/dL |
| Serum Calcium | 9.4 mg/dL | 8.5-10.5 mg/dL |
| Serum Phosphorus | 3.8 mg/dL | 2.5-4.5 mg/dL |
| Magnesium | 1.8 mg/dL | 1.7-2.3 mg/dL |
| TSH | 2.1 mIU/L | 0.4-4.0 mIU/L |
| PTH | 45 pg/mL | 15-65 pg/mL |
| Ferritin | 120 ng/mL | 12-150 ng/mL |

**Synovial Fluid Analysis:**
| Test | Result | Interpretation |
|------|--------|----------------|
| Appearance | Cloudy, yellow | Inflammatory |
| WBC | 35,000/mm3 | Inflammatory |
| PMN | 85% | Neutrophil predominant |
| Crystals | Rhomboid-shaped, weakly positive birefringent | Calcium pyrophosphate dihydrate (diagnostic) |
| Gram Stain | No organisms | Excludes septic arthritis |
| Culture | Pending (ultimately negative) | |

**Imaging:**
- **Knee radiographs:**
  - Chondrocalcinosis: linear calcification in menisci bilaterally
  - Moderate degenerative changes
  - Large effusion

### Diagnosis
**Acute Calcium Pyrophosphate Crystal Arthritis (Pseudogout)**

**Diagnostic Features:**
- CPP crystals identified on polarized microscopy (rhomboid, weakly positive birefringent - blue when parallel to compensator)
- Chondrocalcinosis on radiographs
- Post-surgical trigger (acute illness/surgery commonly precipitates CPPD flares)
- Prior documented episode
- Elderly patient (CPPD prevalence increases with age)

**Secondary Causes Excluded:**
- Primary hyperparathyroidism: normal calcium and PTH
- Hemochromatosis: normal ferritin
- Hypomagnesemia: normal magnesium
- Hypothyroidism: controlled on replacement

### Treatment Plan

**Acute Attack Management:**
1. **Intra-articular corticosteroid injection:** Triamcinolone 40 mg injected after aspiration
   - Preferred given recent surgery, diabetes, and anticoagulation limiting systemic options
2. **Ice, rest, elevation**
3. **Physical therapy:** May resume once acute inflammation subsides

**Systemic Options if Needed:**
- Low-dose colchicine (0.6 mg BID) if flare recurs
- Short course oral prednisone if multiple joints involved

**Prophylaxis (if recurrent):**
- Consider low-dose colchicine 0.6 mg daily for frequent flares

**Follow-up:**
- Continue DVT prophylaxis as planned
- Resume physical therapy when tolerated
- No disease-modifying therapy exists for CPPD (unlike gout)

### Teaching Points
1. **CPPD triggers:** Acute illness, surgery, and trauma commonly precipitate pseudogout attacks; post-operative flares are well-recognized
2. **CPP crystal identification:** Rhomboid or rod-shaped, weakly positive birefringent (blue when parallel to compensator) - opposite to MSU crystals
3. **Chondrocalcinosis:** Radiographic calcification of cartilage (menisci, triangular fibrocartilage, pubic symphysis) supports diagnosis
4. **Secondary causes:** Check calcium/PTH, ferritin, magnesium in younger patients or those with severe disease; less necessary in typical elderly presentation
5. **No disease-modifying therapy:** Unlike gout, no treatment dissolves CPP crystals or prevents deposition; management is symptomatic
6. **Knee predominance:** The knee is the most commonly affected joint in CPPD (unlike first MTP in gout)