Izumi taught the Elric brothers (Edward and Alphonse) alchemy and fighting skills. She is one fo the few people who can truly beat Ed and Al on a regular basis. Izumi is truly and expert fighter and alchemist.
She is married to the butcher Sig (sometimes translated 'Sigu') Curtis.
Before she met the Elrics, she had a son who died during or soon after birth. Izumi was hearkbroken, and tried to revive the child using human transmutation. The transmutation was unsuccessfully, and caused Izumi to loose all of her internal organs from her (roughly) diaphragm down. Somehow, though, she survived, though she is apt to cough blood at inopportune moments. Upon trying the transmutation, she saw the Gate, and is able to perform alchemy without a transmutation circle.
The creature she created when trying to revive her child was a deformed thing with bulging eyes and an oversized head. Izumi gave it back to the Gate, though hse showed signs of regretting her desision the moment the child was out of her hands. The child returned as the homunculus Wrath years later. Izumi tried to protect the homunculus, despite the fact that he tried to kill her, feeling that it was still her child, or, at the very least, her responsibility.
In the Fullmetal Alchemist Movie, Izumi has died because of her missing organs, but appears briefly as a glowing form to embrace Wrath as he dies.
Izumi Curtis has dreadlocks.