A 60-year-old male presents with acute onset of pain, swelling, and redness in his knee joint. His laboratory findings show the presence of calcium pyrophosphate dihydrate (CPPD) crystals in the synovial fluid. What is the most likely cause of this condition?
A. Tuberculous arthritis
B. Leprosy
C. Infective endocarditis
D. Osteoporosis
E. Pyrophosphate crystal arthropathy
Correct Answer: E. Pyrophosphate crystal arthropathy (Pseudogout)
Explanation:
Pseudogout, also known as pyrophosphate crystal arthropathy, is a type of arthritis caused by the deposition of calcium pyrophosphate dihydrate (CPPD) crystals in the joints, leading to acute inflammation, pain, and swelling. It typically affects larger joints, especially the knee, wrist, or elbow.
Key Features Supporting Pyrophosphate Crystal Arthropathy:
- Calcium Pyrophosphate Deposition (CPPD):
- Pseudogout is caused by the accumulation of CPPD crystals in the joint, leading to acute arthritis that mimics gout (but is not caused by uric acid crystals).
- Acute Joint Pain and Swelling:
- Pseudogout often presents as sudden, severe pain, and swelling in the affected joint, typically the knee or wrist.
- Synovial Fluid Analysis:
- The diagnosis is confirmed by polarized light microscopy of joint fluid, which reveals rhomboid-shaped CPPD crystals that are positively birefringent.
- Risk Factors:
- Age (most common in individuals over 60), genetic factors, joint trauma, and conditions such as osteoarthritis and hyperparathyroidism increase the risk of developing pseudogout.
Why Other Options Are Incorrect:
A. Tuberculous Arthritis:
- Tuberculous arthritis is caused by Mycobacterium tuberculosis infection, typically affecting large joints like the hip or knee, and presenting with chronic pain, swelling, and often draining sinuses, not acute inflammation due to crystal deposition.
B. Leprosy:
- Leprosy can affect the joints, leading to neuropathic joint damage, but it is not associated with the formation of calcium pyrophosphate crystals. The presentation involves numbness, skin lesions, and peripheral nerve damage.
C. Infective Endocarditis:
- Infective endocarditis can cause immune complex deposition in the joints (e.g., Osler nodes or Janeway lesions), but it does not involve calcium pyrophosphate deposition. Joint pain in endocarditis is typically due to septicemia or embolic phenomena, not crystal-induced inflammation.
D. Osteoporosis:
- Osteoporosis is a condition characterized by low bone density and an increased risk of fractures, but it does not cause joint inflammation or the deposition of pyrophosphate crystals. The primary issue in osteoporosis is bone fragility, not crystal-induced arthritis.
Further Investigations:
- Joint Fluid Analysis:
- Polarized light microscopy to identify rhomboid-shaped and positively birefringent crystals, confirming the diagnosis of pseudogout.
- X-rays:
- X-ray findings may show chondrocalcinosis, which is the calcification of cartilage, often seen in pseudogout.
- Blood Tests:
- Serum uric acid levels are normal or low in pseudogout, distinguishing it from gout, where uric acid levels are elevated.
Management:
- Acute Attacks:
- Nonsteroidal anti-inflammatory drugs (NSAIDs): First-line treatment for acute pseudogout attacks.
- Colchicine: Can also be used to treat acute episodes.
- Corticosteroids: Either oral or intra-articular steroids may be used to reduce inflammation in acute attacks.
- Long-term Management:
- Treatment focuses on managing underlying conditions such as osteoarthritis or hyperparathyroidism that may contribute to pyrophosphate deposition.
- Joint protection and physical therapy may be recommended to improve function and prevent further joint damage.
Conclusion:
Pseudogout (or pyrophosphate crystal arthropathy) is caused by the deposition of calcium pyrophosphate dihydrate crystals in the joints. It typically affects older adults and presents as acute, painful joint inflammation. Synovial fluid analysis is crucial for diagnosis, and treatment focuses on managing acute symptoms and underlying risk factors.