Pharmaceutical compositions and single unit dosage forms of (+)-2-[1-(3-ethoxy-4-methoxy-phenyl)-2-methanesulfonyl-ethyl]-4-acetylaminoisoindoline-1,3-dione, or a pharmaceutically acceptable stereoisomer, prodrug, salt, solvate, hydrate, or clathrate thereof, are provided herein. Also provided are methods of treating, managing, or preventing various diseases or disorders.