pemphigus vs autoimmune disease

pemphigus and autoimmune disease both are nouns.

Word	Noun	Adjective	Verb	Adverb
pemphigus	Yes	No	No	No
autoimmune disease	Yes	No	No	No

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

pemphigus: a skin disease characterized by large thin-walled blisters (bullae) arising from normal skin or mucous membrane
autoimmune disease: any of a large group of diseases characterized by abnormal functioning of the immune system that causes your immune system to produce antibodies against your own tissues

Other hypernyms of pemphigus include autoimmune disorder, disease of the skin, skin disease, skin disorder.

pemphigus (noun)	autoimmune disease (noun)
a skin disease characterized by large thin-walled blisters (bullae) arising from normal skin or mucous membrane	any of a large group of diseases characterized by abnormal functioning of the immune system that causes your immune system to produce antibodies against your own tissues