Acute gouty synovitis associated with "urate milk"

To analyze the clinical features of acute gouty synovitis associated with thick, milky white, "chalky," urate laden synovial effusions, and to investigate the effects on synovial white blood cell (WBC) counts when leukocyte-rich rheumatoid effusions are incubated with a urate packed milky synovial fluid.

Five patients (all men, mean age 70.8 years) with acute gouty synovitis (acute arthritis in 3, acute bursitis in 2) associated with "urate milk" were studied between 1993 and 1996.

Synovial effusions were thick, "chalky," and appeared "milky" white. The fluids were packed with monosodium urate (MSU) crystals, which sedimented upon standing, leaving a clear supernatant containing a few MSU crystals. The presence of massive amounts of MSU crystals and crystal clumps interfered with accurate determination of synovial WBC counts. Four fluids showed "a few leukocytes," and one a WBC count of 6750/mm3 with 91% neutrophils and several intraleukocytic crystals. Four patients had subcutaneous tophi. Of the risk factors associated with development of gout, the most frequent was ethanol abuse, in 4 and possibly all 5 patients. Incubation of leukocyte-rich rheumatoid synovial effusions with urate laden knee fluid from Patient 5 produced a greater reduction in synovial WBC counts compared to controls.

Milky white synovial effusions containing massive quantities of urate crystals (referred to as "urate milk") may rarely occur in the setting of acute gouty arthritis or bursitis. Ethanol abuse appears to be a risk factor associated with the development of hyperuricemia and gout in these patients.