These are good resources for obtaining an overview of medical syndromes and eponymic (meaning named after the person who discovered or described the condition first) diseases. They are arranged alphabetically by disease or syndrome and will provided helpful synonyms.
Dictionary of Medical Syndromes
Sergio Magalini and Sabina Magalini 4th ed. c1997
Jablonski's Dictionary of Syndromes & Eponymic Diseases
Stanley Jablonski 2nd ed. c1991
NORD Compendium of Diseases & Disorders (NORD Online)
National Organization of Rare Diseases