atypical pneumonia vs primary atypical pneumonia

atypical pneumonia and primary atypical pneumonia both are nouns.

Word	Noun	Adjective	Verb	Adverb
atypical pneumonia	Yes	No	No	No
primary atypical pneumonia	Yes	No	No	No

As nouns, atypical pneumonia and primary atypical pneumonia are synonyms defined as:

atypical pneumonia and primary atypical pneumonia: an acute respiratory disease marked by high fever and coughing; caused by mycoplasma; primarily affecting children and young adults

Other synonyms of atypical pneumonia include mycoplasmal pneumonia.

atypical pneumonia (noun)	primary atypical pneumonia (noun)
an acute respiratory disease marked by high fever and coughing; caused by mycoplasma; primarily affecting children and young adults	an acute respiratory disease marked by high fever and coughing; caused by mycoplasma; primarily affecting children and young adults