What is the likely diagnosis for a 54-year-old female presenting with recurrent, tender, and warm swelling between the thumb and index finger, with a history of similar symptoms in the foot, knee, and hip, and no history of trauma?

Likely Diagnosis: Gout

The most likely diagnosis is gout, given the recurrent episodes of acute, tender, warm swelling affecting multiple joints (hand, foot, knee, hip) with spontaneous partial resolution followed by recurrence, particularly in a 54-year-old female. 1

Key Diagnostic Features Supporting Gout

• Recurrent acute inflammatory episodes: The pattern of swelling that "started going down but restarted 2 days ago" is classic for gout flares, which characteristically have an abrupt onset and can spontaneously improve before recurring 1

• Migratory polyarticular involvement: Gout should be considered in any acute arthritis in an adult, and the history of similar episodes in the foot, knee, and hip indicates a pattern of recurrent inflammatory arthritis affecting different joints over time 1

• Inflammatory signs: The combination of tenderness and warmth indicates active inflammation, consistent with crystal-induced arthritis 1

• Location between thumb and index finger: This likely represents the first metacarpophalangeal (MCP) joint or adjacent soft tissue, which can be affected by gout, though gout more classically targets the first metatarsophalangeal joint of the foot 1

Critical Differential Diagnoses to Consider

Psoriatic Arthritis

• Can present with recurrent inflammatory episodes affecting DIP joints or single digits (dactylitis/"sausage digit") 1
• May show asymmetric involvement and can affect the hand between thumb and index finger 1
• However, typically associated with psoriatic skin lesions and nail changes, which are not mentioned in this case 1

Erosive Hand Osteoarthritis

• Can present with inflammatory symptoms including soft tissue swelling, erythema, and warmth 1
• Typically has abrupt onset with marked pain and inflammatory signs 1
• However, less likely to cause the migratory pattern affecting large joints like knee and hip 1

Rheumatoid Arthritis

• Less likely given the location, as RA typically spares DIP joints and primarily targets MCP, PIP joints, and wrists in a symmetric pattern 2, 3, 4
• Morning stiffness lasting >1 hour would be expected but is not described 4

Recommended Diagnostic Approach

Immediate next step: Synovial fluid aspiration and crystal analysis 1

• Demonstration of monosodium urate (MSU) crystals allows definitive diagnosis of gout and should be performed in every person with suspected gout 1

• If synovial fluid aspiration is not feasible, clinical diagnosis is supported by: monoarticular involvement of foot or ankle, previous similar acute episodes, rapid onset of severe pain and swelling (worst in <24 hours), erythema, female gender, and hyperuricemia 1

Additional investigations when crystal identification is not possible:

• Ultrasound scanning can detect tophi not evident on clinical examination or the "double contour sign" at cartilage surfaces, which is highly specific for urate deposits 1

• Plain radiographs have limited value for acute gout flare diagnosis but can show MSU crystal deposition in chronic disease 1

• Serum uric acid level, though diagnosis should not be made on hyperuricemia alone 1

• ESR and CRP to assess inflammatory activity 1

Common Pitfalls to Avoid

• Do not diagnose gout based solely on elevated serum uric acid - crystal identification is the gold standard 1

• Gout can superimpose on pre-existing osteoarthritis, complicating the clinical picture 1, 5

• Normal serum uric acid does not exclude gout during an acute flare, as levels may be transiently normal or low 1

• Consider that the hand location between thumb and index finger could represent thumb base involvement, which would favor osteoarthritis, but the acute inflammatory presentation with recurrence and involvement of other large joints strongly favors crystal arthropathy 1, 5