American Board of Internal Medicine (ABIM) Certification Practice Exam

What does the presence of crystals within neutrophils in synovial fluid indicate?

1. Chronic gout

2. Active gout

3. Rheumatoid arthritis

4. Psoriatic arthritis

The correct answer is: Active gout

The presence of crystals within neutrophils in synovial fluid is a key indicator of active gout. In cases of gout, hyperuricemia leads to the formation of monosodium urate crystals, which can be phagocytosed by neutrophils. When these neutrophils, containing the phagocytosed crystals, are observed in a synovial fluid sample, it signifies that there is an active inflammatory process occurring due to the acute attack of gout. This finding is crucial for diagnosing acute gout as it directly correlates with the inflammation associated with the presence of urate crystals in the joint. The detection of these crystals helps differentiate gout from other forms of arthritis, as they are not typically found in rheumatoid arthritis, psoriatic arthritis, or chronic forms of gout. Instead, in chronic gout, one might find more fibrosis or chronic inflammatory changes without the acute neutrophilic response evident in an active gout attack. Therefore, the identification of crystals in neutrophils is specifically indicative of active gout, supporting the diagnosis during an acute episode.