A diffuse, non-pitting induration of the skin of unknown etiology that occurs most commonly in association with diabetes mellitus, predominantly in females. It typically begins on the face or head and spreads to other areas of the body, sometimes involving noncutaneous tissues. Often it is preceded by any of various infections, notably staphylococcal infections. The condition resolves spontaneously, usually within two years of onset. (From Dorland, 27th ed).