A decrease in the number of circulating neutrophils (both segmented and band forms), strictly defined as an absolute total neutrophil count (ANC) of <1,500/μL in children >1 year of age, <1,000/μL in children <1 year of age, and <5,000/μL in the 1st week of life
- To calculate ANC, multiply the total WBC count by the percentage of segmented neutrophils and band forms.
- For example: WBC count 5,200/μL with 15% segs/polys, 4% bands, 76% lymphocytes, 5% monocytes: ANC = 5,200 × (0.15 + 0.04) = 988
- Severe neutropenia is defined as an ANC <500/μL.
- Normal values for total WBC counts and ANC vary with age and race.
- Children of some ethnic groups, including African and Middle Eastern groups, have lower total WBC counts and lower ANCs than do Caucasian children.
- Lower end of normal range for ANC may be 800/μL in 30% of African Americans and does not represent an increased risk for infection.
- Infants have a higher total WBC count and a higher percentage of lymphocytes in their differential counts.
- Prevalence of congenital and idiopathic neutropenia: 2.1 cases per million in the United States
- Incidence of neonatal alloimmune neutropenia: 2 per 1,000 live births
- A number of mutations causing severe congenital neutropenia have been identified.
- Autosomal recessive: HAX1 (Kostmann syndrome), G6PC3, SBDS (Shwachman-Diamond syndrome), others
- Autosomal dominant: ELANE, GFL1, GATA2, others
- X-linked: WASP, TAZ (Barth syndrome), others
- Cyclic neutropenia: autosomal dominant or sporadic (ELANE)
Decreased phagocytic activity due to decreased numbers of neutrophils
- Decreased production of neutrophils
- Viral suppression
- Marrow suppression by drugs, chemotherapy, or radiation
- Nutritional deficiencies
- Primary disorders of myelopoiesis
- Increased destruction of neutrophils
- Immune-mediated destruction
- Increased use (usually with overwhelming infection)
- Sequestration in the spleen
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