Leukopenia (from Greek λευκός (leukos) 'white', and πενία (penia) 'deficiency') is a decrease in the number of leukocytes. Found in the blood, they are the white blood cells, and are the body's primary defense against an infection. Thus the condition of leukopenia places individuals at increased risk of infection. Symptoms may include mouth or skin sores, sore throat, cough, trouble breathing, feeling light-headed, fever, chills, or body aches.
Neutropenia, a subtype of leukopenia, refers to a decrease in the number of circulating neutrophil granulocytes, the most abundant white blood cells. The terms leukopenia and neutropenia may occasionally be used interchangeably, as the neutrophil count is the most important indicator of infection risk. Agranulocytosis is an acute form of neutropenia.