(nekrŏ-tīz-ing ŭlsĕr-ă-tiv perē-ō-don-tītis) Severe and rapidly progressive disease with distinctive erythema of the free gingiva, attached gingiva, and the alveolar mucosa; extensive soft tissue necrosis that usually starts with the interdental papillae and marked loss of periodontal attachment. AcronymsSeeNUP