agranulocytosis (əgrănˌyəlōsĪtōˈsis) [key], disease in which the production of granulated white blood cells by the bone marrow is impaired. Although the disease may occur spontaneously it is usually induced by exposure to antithyroid drugs, sulfonamides, phenothiazines, chemotherapy, and radiation therapies. Granulocytes protect the body against infectious agents; their depletion results in severe respiratory infections, ulceration of the mouth and colon, high fever, and prostration. These symptoms may occur suddenly or over a period of days or weeks. Penicillin is usually the drug of choice to combat the bacterial invasion. Treatment may require bone marrow transplants to start the production of healthy white blood cells. The fatality rate is high (approaching 80%) in untreated cases, and deaths are common even with antibiotic treatment.