What oral disease causes your gums to be inflamed?

Infection, abscess.. All of the followings: 1) gum disease/infection of the gum, 2) dental or periodontal abscess, 3)faulty restoration/open contacts that cause food impaction, 3)malocclusion, 4)open mouth breather, 5)dry mouth syndrome or any oral condition causing dry mouth, 6)lichen planus and other autoimmune diseases, 7)allergic reaction.
Gingivitis.. .. And the more advanced periodontitis. Xerostomia, although not a disease but rather a side effect of other medical problems or medications, can also cause gingival inflammation. Acid reflux and carious lesions are also contributors. Have yourself examined by your local dentist.