Neutropaenia is a common incidental finding on routine blood studies. This manuscript will focus on the possible causes, challenging differential diagnosis and appropriate management of neutropaenia. Different mechanisms may explain a decreased production, impaired development or increased destruction of neutrophilic granulocytes. We distinguish between congenital and acquired causes. The former includes benign ethnic neutropaenia, severe congenital neutropaenia and cyclic neutropaenia. For the latter, infections, drugs, auto-immune reactions, nutritional deficiencies as well as haematological malignancies are all possible reasons of neutropaenia. The risk of infection in those with non-chemotherapy-induced neutropaenia mainly depends on the bone marrow reserve. Asymptomatic patients with mild or moderate neutropaenia can be observed with serial blood counts at increasing intervals. Infections should always be treated according to the severity of neutropaenia. Therapy with growth factors, drug discontinuation and immunosuppressive therapy can be considered depending on the underlying cause.

(BELG J HEMATOL 2019;10(3):103–12)