LEUKOPENIA - decrease in the number of leukocytes in the blood (less than 4000 in 1 μl, or 4.0-109 / l). It is observed in typhoid fever, brucellosis, influenza, poliomyelitis, viral hepatitis, liver cirrhosis, malaria, leishmaniasis, aplastic and pernicious anemia , exposure to ionizing radiation, etc. Leukopenia occurs when you take certain medications (amidopyrine, butadion, anesthyprityluria, etc.). persons with hypersensitivity to them. The most common form is neutropenia (a decrease in the neutrophil content), less frequently lymphocytopenia (low content of lymphocytes). See also Agranulocytosis .