Diagnostic common feature of oral submucous fibrosis is-

Oral submucous fibrosis (OSMF) is a chronic, progressive, potentially malignant disorder strongly associated with areca nut (betel quid) chewing. Its most characteristic and diagnostic clinical finding is the presence of palpable fibrous bands in the buccal mucosa, soft palate, and retromolar areas, which cause progressive stiffness, blanching of the mucosa, and restricted mouth opening (trismus). While generalized mucosal fibrosis occurs throughout the disease, the palpable circumoral/vertical fibrous bands are the key diagnostic clinical sign used to identify and stage the condition.

Reference: Rajendran R, Sivapathasundharam B. Shafer's Textbook of Oral Pathology, 8th ed. – Oral Submucous Fibrosis.