Lyme arthritis vs Lyme disease

Lyme arthritis and Lyme disease both are nouns.

Word	Noun	Adjective	Verb	Adverb
Lyme arthritis	Yes	No	No	No
Lyme disease	Yes	No	No	No

As nouns, Lyme arthritis and Lyme disease are synonyms defined as:

Lyme arthritis and Lyme disease: an acute inflammatory disease characterized by a rash with joint swelling and fever; caused by bacteria carried by the bite of a deer tick

Lyme arthritis (noun)	Lyme disease (noun)
an acute inflammatory disease characterized by a rash with joint swelling and fever; caused by bacteria carried by the bite of a deer tick	an acute inflammatory disease characterized by a rash with joint swelling and fever; caused by bacteria carried by the bite of a deer tick