A 29-year-old male patient complains of gingival hemorrhages during tooth brushing, and bad breath. Objectively: gingival papillae and marginal gingiva are hyperemic with a cyanotic tint, bleed on probing. Periodontal pockets are 3-3,5 mm deep, with serous exudate expressed from them. The sub- and supragingival calculus is present. Orthopantomograph shows osteoporosis of the alveolar process, resorption of interalveolar septa to 1/3. What is the most likely diagnosis?