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.

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