A 37-year-old patient addressed a dental surgeon with complaints of deteriorating welbeing, high fever up to 38, 1°C, headache, painful swelling on the chin. Objectively: there is a dense painful infiltration 3x4 cm in size on the skin of the chin. The skin over the infiltration is bluish in color. There are four necrosis areas in the focal center around the hair follicles. The submental lymph nodes are enlarged and painful on palpation. Make the diagnosis: