Diagnosis and management of neutropenia in adults: Expert guidance

Summary Neutropenia in general is defined as a blood neutrophil count of less than 1.5 × 10 9 /L, in severe neutropenia counts drop to less than 0.5 × 10 9 /L, but the definition of neutropenia varies according to the patient's ethnic origin and age. For Caucasian adults, the absolute neutrophil count (ANC) threshold of 1.8 × 10 9 /L is adopted for the definition of neutropenia according to the World Health Organization (see Fioredda et al. (1)). It can be inherited or acquired, and it is an uncommon haematological finding in adult outpatient clinics. Neutropenia can result from decreased production of neutrophil precursors in the bone marrow, as in the case of severe congenital neutropenia, or from increased utilization of neutrophils in some bacterial infections, or accelerated destruction as is the case with drug‐induced neutropenia, viral infections and autoimmune neutropenia. Severe chronic neutropenia increases susceptibility to bacterial or fungal infections. Treating severe chronic neutropenia patients with granulocyte colony‐stimulating factor (G‐CSF) can increase neutrophil counts for most types of neutropenia. This article will provide guidance on diagnosing and managing severe chronic neutropenia in adult patients and provides a transition programme from adolescence to adulthood.