What condition is indicated by a leukocyte count of 90,000/mm3 in synovial fluid with primarily neutrophils?

• A. Gout
• B. Rheumatoid arthritis
• C. Septic arthritis
• D. Osteoarthritis

Answer: (C)

A leukocyte count of 90,000/mm3 in synovial fluid, particularly with a predominance of neutrophils, is highly indicative of septic arthritis. Septic arthritis is characterized by an acute inflammatory response to infection in the joint space, typically caused by bacteria. The exceedingly high leukocyte count reflects the significant inflammatory response, with neutrophils being the primary white blood cells involved, as they are the first responders to bacterial infections.

In the context of other conditions like gout, rheumatoid arthritis, and osteoarthritis, the leukocyte counts differ significantly. Gout typically features a lower white blood cell count with the presence of monosodium urate crystals but may also show elevated counts in an acute attack. Rheumatoid arthritis may have an elevated leukocyte count too, but not usually to the extent seen in septic arthritis, and the cells tend to be more of a mixed population rather than predominantly neutrophils. Osteoarthritis is primarily associated with a non-inflammatory synovial fluid profile or a mild increase in white blood cells, generally below the threshold characteristic of inflammatory or infectious conditions.

Therefore, the combination of a dramatic leukocyte elevation and a neutrophil predominance strongly points toward a diagnosis of septic arthritis, where prompt diagnosis and intervention are