primary atypical pneumonia vs atypical pneumonia

primary atypical pneumonia and atypical pneumonia both are nouns.

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

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

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

Other synonyms of primary atypical pneumonia include mycoplasmal pneumonia.

primary atypical pneumonia (noun)	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