FEATURE vs SYMPTOMS/SIGNS:
Feature is a symptom or a sign without which a disease is almost always not there (remember there is nothing 100% in medicine except death). A few examples are:
1: Itching is a feature of PBC, so PBC will almost always have itch. If there is no itching it’s not PBC.
2: Loud P2 is a feature of significant Pulmonary Hypertension.
For students n junior doctors, when an authentic medical book writes the word “feature”, take it seriously and understand it.
Other important words used with similar meaning are pathognomonic and hallmark, but features is different from these. Pathognomonic if present confirms the disease, feature if absent excludes the disease.
This is my understanding what I was taught by my teachers. I will welcome any input from colleagues.