case-by-case vs item-by-item

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

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

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

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

Other synonyms of case-by-case include individual.

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