In crystallographic study of tophaceous substances and deposits in gouty synovial fluids using differential-interference microscopy, polarized light microscopy and X-ray diffraction method, the following results were obtained.
1) Substances of subcutaneous tophi and deposits in gouty synovial fluids were found to be needle-like crystals. By polarized-light microscopy, they were negatively birefringent with extinction on the long axis.
2) The needle-like crystals obtained from subcutaneous tophi and/or synovial fluids in gouty patients have been positively confirmed as monosodium urate monohydrate (NaC5H3N4O3·H2O) by X-ray diffraction technics.
