item-by-item vs case-by-case

item-by-item and case-by-case both are adjectives.

Word	Noun	Adjective	Verb	Adverb
item-by-item	No	Yes	No	No
case-by-case	No	Yes	No	No

As adjectives, item-by-item and case-by-case are synonyms defined as:

item-by-item and case-by-case: separate and distinct from others of the same kind

Other synonyms of item-by-item include individual.

item-by-item (adjective)	case-by-case (adjective)
separate and distinct from others of the same kind	separate and distinct from others of the same kind