Neutropenia

An abnormally low absolute neutrophil count in peripheral blood (<1.5 × 10⁹ cells/L), impairing innate immune defense and predisposing to bacterial and fungal infections. Possible causes are medications (chemotherapy, radiotherapy, antibiotics, anticonvulsants, antihypertensive), malignancy (leukemia, lymphoma, myelodysplastic syndrome), aplastic anemia, infections (sepsis, HIV, EBV, influenza, tuberculosis, malaria), nutritional deficiency (vitamin B12, folate, copper), autoimmune conditions (lupus, rheumatoid arthritis, Felty syndrome), genetic conditions (Kostmann syndrome, cyclic neutropenia), and hypersplenism.