Addison disease: Long-term underfunction of the outer portion of the adrenal gland. In medical terms, chronic insufficiency of the adrenal cortex. This may be due to a number of different insults to the adrenal including physical trauma, hemorrhage, and tuberculosis of the adrenal, and destruction of the cells in the pituitary gland that secrete ACTH (adrenocorticotropic hormone) which normally drives the adrenal. Addison's disease is characterized by bronzing of the skin, anemia, weakness, and low blood pressure. The U.S. President J.F. Kennedy is said to have had Addison disease. Named after the British physician Thomas Addison (1793-1860).When Addison first identified adrenal insufficiency in 1849, tuberculosis (TB) was responsible for 70-90% of cases. As the treatment for TB improved, the incidence of adrenal insufficiency due to TB of the adrenal glands greatly decreased. TB now accounts for around 20% of cases of primary adrenal insufficiency in developed countries.