disease of the skin vs disease

disease of the skin and disease both are nouns.

Word	Noun	Adjective	Verb	Adverb
disease of the skin	Yes	No	No	No
disease	Yes	No	No	No

As nouns, disease is a hypernym of disease of the skin; that is, disease is a word with a broader meaning than disease of the skin:

disease of the skin (noun)	disease (noun)
a disease affecting the skin	an impairment of health or a condition of abnormal functioning