Watercolor drawing of the left hand of a woman, aged 63 years, suffering from chronic gout. Both hands are extremely disfigured by large tophi. The skin over these tophi has in parts ulcerated. A tophus is a deposit of uric acid crystals, in the form of monosodium urate crystals, in people with longstanding hyperuricemia (high levels of uric acid in the blood). Tophi are pathognomonic for the disease gout. By Leonard Mark, 1895.