Acute monoarthritis associated with lipid liquid crystals

We describe three women with unexplained acute monoarthritis and birefringent lipid spherules or lipid liquid crystals in their synovial fluid. Synovial fluid aspirated within 24 hours of onset showed leucocyte counts ranging from 10 X 10(9) to 46 X 10(9)/1 with 91-95% polymorphonuclear cells. Numerous positively birefringent 2-6 micron microspherules were seen inside and outside polymorphonuclear cells. These were dissolved in alcohol-ether but were not digested by uricase. Other non-birefringent globules of similar size that stained with Sudan black B were also seen. Transmission electron microscopy identified osmiophilic homogeneous or multilamellated material in phagocytic vacuoles. Serum lipids, lipase, and repeated joint radiographs were normal. Arthritis subsided completely after treatment with colchicine in one patient and nonsteroidal anti-inflammatory agents in two. Thus birefringent microspherules can be found in association with acute, otherwise unexplained, arthritis. It seems possible that certain lipid liquid crystals may induce synovial inflammation similar to inflammation seen in other crystal induced arthritides.