Disease
Syndrome
suffix, な adjective
See this on the end of a word, and you know that it is a ______symptom. When you have a _____symptom, you have some kind of disease or syndrome (otherwise why would you have a symptom of some kind?).
Since this is attached to things, it's treated like a jukugo word, so the on'yomi reading is used here.
妻の神経性ヒステリー症について、医者に相談しなくてはいけません。
I should consult a doctor about my wife’s neurotic hysteria.