hypoplastic dwarf vs nanus

hypoplastic dwarf and nanus both are nouns.

Word	Noun	Adjective	Verb	Adverb
hypoplastic dwarf	Yes	No	No	No
nanus	Yes	No	No	No

As nouns, nanus is a hypernym of hypoplastic dwarf; that is, nanus is a word with a broader meaning than hypoplastic dwarf:

hypoplastic dwarf: an achondroplastic dwarf whose small size is the result of a genetic defect; body parts and mental and sexual development are normal
nanus: a person who is markedly small

Other hypernyms of hypoplastic dwarf include dwarf, midget.

hypoplastic dwarf (noun)	nanus (noun)
an achondroplastic dwarf whose small size is the result of a genetic defect; body parts and mental and sexual development are normal	a person who is markedly small