Twelver Shi'ism believes that the line of succession to the Prophet ended with the twelfth imam.
It is important to distinguish between an ism and a mere generalization about group differences. Generalizations that have statistical validity are not isms. An ism assumes that the generalization applies to an individual.
heterosexism (from heterosexual).
Shakespeareanism (coined after William Shakespeare).
hyperthyroidism, hypothyroidism.
masculism (from masculus, Latin for male).