Acute monoarthritis associated with intracellular positively birefringent Maltese cross appearing spherules

A 57-year-old black woman presented with acute monoarthritis of the left knee. Numerous intra and extracellular strongly positively birefringent lipid spherules with a Maltese cross appearance were seen in the synovial fluid from the affected joint when viewed under compensated polarized light microscopy. This represents the 7th reported case of atraumatic acute arthritis associated with large numbers of positively birefringent lipid spherules. We review previous case reports and discuss the present understanding of the pathogenesis and the significance of the association of large numbers of birefringent lipid spherules with acute arthritis.