progeria, any of several rare human disorders associated with premature aging. The two major types of progeria are Hutchinson-Gilford progeria syndrome (HGPS), which has its onset in early childhood, and Werner syndrome (adult progeria), which occurs later in life. A third condition, Hallerman-Streiff-François syndrome, is characterized by the presence of progeria in combination with dwarfism and other features of abnormal growth. Progeria is extremely rare; for example, the global incidence of Hutchinson-Gilford progeria syndrome is approximately one in every four to eight million births. Signs of Hutchinson-Gilford progeria syndrome appear at about age one, after an evidently normal infancy. Affected ...(100 of 464 words)