Discussion
Gout is caused by the precipitation of uric acid crystals into a joint. Attacks are usually monoarticular as opposed to polyarticular. The presence of hyperuricemia is variable; some patients have high serum uric acid levels and never experience gout, while other patients have normal serum uric acid levels and experience gout attacks. The condition is more common in men than in women. There are multiple risk factors for the development of gout, including obesity, hypertension, chronic kidney disease, regular excessive consumption of alcohol, taking diuretics, and consuming foods high in fructose corn syrup.1 The joints most often affected are the great toe and knee. Patients with gout typically complain of pain, swelling, redness, and increased warmth in the affected area.
Unfortunately, the clinical presentation of an acute gout attack and SA are indistinguishable.2 Risk factors for SA include IV drug abuse, diabetes mellitus, having a prosthetic joint, immunosuppression, and human immunodeficiency virus infection. The only reliable way to distinguish between gout and SA requires arthrocentesis with microscopic examination of the synovial fluid for bacteria, crystals, white blood cell (WBC) count, and culture.2
It is critical not to miss SA because it is associated with significant morbidity and a mortality rate of 11%.2 To further complicate the diagnosis, some patients can experience SA in the setting of an acute gout attack. In a study of all joint aspirations with crystals (both uric acid and calcium pyrophosphate), there was a 5.2% incidence of concomitant infection.2 Similarly, in patients with confirmed SA, crystals were present 21% of the time.2
A gram stain of the synovial fluid is highly specific, but only positive in 59% of cases of SA. Therefore, a negative gram stain does not exclude the diagnosis. Similarly, the presence of crystals does not exclude a coexisting joint infection. If there is high clinical suspicion for SA or an elevated synovial WBC, the patient should be presumed to have SA and treated as such until cultures prove otherwise.
It is unclear if this patient had SA. However, an EP is taking a risk in diagnosing an acute gout attack based solely on a patient’s history and physical examination. The EP should always be mindful that gout and SA can present with the identical signs and symptoms, and can present concomitantly.