Age / Sex : 68 / M

Chief Complaint: painful swelling of Right hand for 10 days

Findings:

B hand AP view shows localized soft tissue swelling with subtle amorphous radiopaque density in radial side of Right 1^st MCP joint.

CT coronal reconstruction image shows juxtacortical soft tissue mass with amorphous calcifications in the radial side of right 1^st MCP joint. Focal cortical erosion is noted in the head of 1^st metacarpal bone. The joint space is relatively preserved.

MR images show a lobulated, periarticular soft tissue mass in radial side of 1^st MCP joint. This mass is isosignal (compared to muscle) with low signal intense nodules on T1WI, hyper to hyposignal intensity with low signal intense nodules on fat suppression T2WI. Contrast enhanced image shows heterogeneous enhancement in this mass. The cortex of 1^st metacarpal bone is focally eroded, with patch bone marrow edema. The extensor pollicis longus tendon is displaced by this mass.

Discussion

Gout is disorder of purine metabolism. Gouty arthritis is common in the foot, but it can also occur in the hand. A systematic clinical examination along with radiographs and aspiration cytology confirms. Longstanding hyperuricemia produce deposition of monosodium urate (MSU) crystals in and around the joints. Laboratory finding is elevated serum urate level above 6 mg/dL (in women) or 7 mg/dL (in men). Tophus is a chronic foreign-body granulomatous response to MSU crystals. In early phase, 1^st MTP joint is most commonly involved. As the disease is progressive, the involved joints are extended from lower extremity to upper extremity, from small peripheral joints to large joints, from mono- or oligo-articular to polyarticular joints. In hand and wrist, distal interphalangeal joints are commonly involved. Clinical phase are classified as 1) asymptomatic hyperuricemia (hyperuricemia prior to onset of clinical symptom), 2) acute gouty arthritis (acute symptomatic joint inflammation with systemic manifestations), 3) intercritical gout (asymptomatic gout between attachs), 4) chronic tophaceous gout (repeated attacks, chronic destructive polyarticular arthritis). Radiologically, plain radiograph shows normal for early 7-10 years.

Gout is asymmetrically involved intra- and extra-articular joint space. The joint is eccentrically eroded, with well-circumscribed bone erosion and sclerotic margins, overhanging edges, and expansion of bone ends (bulbous appearance). Tophus is showed as a soft tissue mass with cloudy, amorphous density, occasionally containing fluffy or distinct calcifications. It may saucerize the underlying bone or stimulate periostitis. In advanced, late features, the crystals penetrate intraosseously, making an intra-osseous calcifications, extensive osteolysis, bone destruction with cartilage destruction (from periphery to central), uneven articular space narrowing and ankylosis. MR images show joint effusion, soft tissue and bone marrow edema, synovial pannus, enhancement of paraarticular structures. Bone marrow edema is less common than other inflammatory erosive arthropathies. Tophi may locate intraarticular, subcutaneous or intratendinous area. It shows low to intermediate intense on T1WI, low (calcified) or high (hydration) on T2WI and variable enhancement. Intraosseous gout shows intraosseous tophi with bony cyst and punctuate calcifications.    

References

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