"We were capable of having children, but Astoria was frail. A blood malediction, a serious one. An ancestor was cursed... it showed up in her. You know how these things can resurface after generations..."
-- Draco Malfoy (CC4)
A Maledictus is a witch or wizard who suffers from a blood curse. One form of this affliction, referred to as a “malediction,” had been inherited by Draco Malfoy’s wife Astoria Greengrass. Astoria died from the blood curse in August of 2019 (CC). Another form causes its victim to slowly transform permanently into a beast (CG).
from "malady" = an illness or something that causes one to suffer. According to vocabulary.com: Malady, pronounced "MAL-uh-dee," comes from the Latin words male, meaning "bad or ill" and habitus for "have, hold." (Text from Vocabulary.com, Copyright ©1998-2017 Thinkmap, Inc. All rights reserved.)
A character appears in CG who is described as a Maledictus whose curse will eventually transform her into a beast (CG). Little is known about her as of this writing. However, a number of clues suggest that she might be the "Enchanting Snake Girl" who appears on the posters for the Circus Arcana, including the patterned fabric of her costume.
Fan speculation a year before the film's release is that this woman's name is not given because she will be revealed to be Nagini. The release of the third trailer for the film on 25 September 2018 and a short interview with the Claudia Kim confirmed that she is in fact Nagini.