Question 1: A 40-year old man presented with acute onset pain and swelling of the left great toe. On X-ray, a punched-out lytic lesion is seen on the phalanx with sclerotic margins and overhanging bony edges. What is the most likely diagnosis?
- A. Gout (Correct Answer)
- B. Rheumatoid arthritis
- C. Psoriatic arthritis
- D. Reiter's syndrome
Explanation: ### Explanation
The clinical presentation and radiographic findings are classic for **Gouty Arthritis**.
**1. Why Gout is Correct:**
The patient presents with **Podagra** (acute involvement of the first metatarsophalangeal joint), which is the most common site for gout. The X-ray description is pathognomonic:
* **Punched-out lytic lesions:** These represent intraosseous tophi (monosodium urate crystals).
* **Martel’s Sign (Overhanging edges):** The sclerotic, "rat-bite" erosions with overhanging bony margins are highly characteristic of chronic tophaceous gout. Unlike other inflammatory arthritides, the joint space in gout is often preserved until late stages.
**2. Why Other Options are Incorrect:**
* **Rheumatoid Arthritis (RA):** Typically presents with symmetrical involvement of small joints (MCP, PIP). Radiologically, it shows **periarticular osteopenia** and marginal erosions without sclerotic borders or overhanging edges.
* **Psoriatic Arthritis:** While it can affect the distal phalanges, it is characterized by the "pencil-in-cup" deformity and periosteal new bone formation, not isolated punched-out lesions with sclerotic margins.
* **Reiter’s Syndrome (Reactive Arthritis):** Usually follows a GI or GU infection and presents as an asymmetric oligoarthritis, often involving the heel (Achilles tendonitis) or sacroiliac joints.
**3. High-Yield Pearls for NEET-PG:**
* **Gold Standard Diagnosis:** Polarized light microscopy showing **needle-shaped, negatively birefringent** crystals (Yellow when parallel to the axis).
* **Martel’s Sign:** The radiographic hallmark of gout (overhanging edges).
* **Drug of Choice:** NSAIDs are first-line for acute attacks; **Colchicine** is an alternative. **Allopurinol** (Xanthine oxidase inhibitor) is used for chronic management but should *never* be started during an acute attack.
* **Dietary triggers:** High purine foods (red meat, seafood) and alcohol.