A 33-year-old patient complains about pain, gingival hemorrhage, halitosis, body temperature rise up to 37,8°C. Objectively: gums are apparently hyperaemic, edematic, bleed easily, parodontal pouches are 34 mm deep, and contain purulent exudate. Orthopantomogram shows diffuse osteoporosis of alveolar process, resorption of interdental septa down to 1/3 of their height. What is the most likely diagnosis?