Key Takeaways
✅ Neutropenia is defined as abnormally low number of circulating neutrophils in the peripheral blood, with an absolute neutrophil count (ANC) ≤ 1.5 × 109/L (normal neutrophil counts need to be stratified for age and ethnicity; patients of African or Middle-Eastern descent may have lower neutrophil counts at baseline).
✅ Neutropenia is graded according to severity, which determines risk of infection: mild 1-1.5 × 109/L; moderate 0.5-1 × 109/L; severe < 0.5 × 109/L; most severe/agranulocytosis ≤ 0.2 × 109/L.
✅ Neutropenia can by classified as acute vs. chronic, permanent vs. cyclical, congenital vs. acquired, isolated vs. associated with other cytopenias.
✅ Chronic neutropenia is defined as lasting > 3 months and documented on 3 separate occasions.
✅ Idiopathic neutropenia is neutropenia that is not associated with any cause such as drugs, autoimmune disease, malignancy or dietary deficiency.
✅ Chronic idiopathic neutropenia, then, is an acquired neutropenia lasting for at least for 3 months and not attributable to drugs or a specific genetic, infectious, inflammatory, autoimmune or malignant cause.
✅ Chronic idiopathic neutropenia is a diagnosis of exclusion and is sometimes used synonymously with autoimmune neutropenia. Others reserve the term autoimmune neutropenia for cases of chronic idiopathic neutropenia in which anti-neutrophil antibodies are positive.
✅ Chronic idiopathic neutropenia is usually associated with mild-moderate neutropenia. About 45% of patients have recurrent mouth ulcers, and 25% have infections (though rarely serious).
✅ Treatment is supportive and includes good hygiene, observation for early signs of infection, treatment with antibiotics when infections occur, and rarely G-CSF for patients with recurrent or severe infections or symptomatic mucosal erosions or skin infections.
✅ There is recent evidence that a small subset of patients with chronic idiopathic neutropenia/ autoimmune neutropenia may progress to a clonal bone marrow disorder.