Description

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.

Epidemiology

• 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

Risk Factors

Pathophysiology

Decreased phagocytic activity due to decreased numbers of neutrophils

Etiology

• 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