A 66-year-old man has complains of marked weakness. The onset of the disease was acute: he developed fever and pain in the joints and along the muscles of his legs. He has a violet-cyanotic erythema around his eyes and over the knee joints. His heart rate is 120/min., heart sounds are weakened. Blood test: leukocytes – 12 · 109/L, ESR – 40 mm/hour. Make the right diagnosis: