Neutropenia

Etiologies

Constitutional neutropenia: mild (ANC>1000), chronic
Benign ethnic neutropenia: mild (ANC>1000), chronic, usually in patients with Mediterranean or African ancestry
Benign familial neutropenia: same as above, but hereditary and not associated with a specific ethnicity
Cyclic neutropenia: hereditary, with severe neutropenia on a 21-day cycle since childhood
Others: severe congenital neutropenia, Schwachman-Diamond syndrome, Fanconi anemia, dyskeratosis congenita, Chediak-Higash syndrome, myelokathesis, Griscelli syndrome II, and cartilage-hair hypoplasia

Infectious
- Active infection, particularly viral, but including severe sepsis from any cause; more common in the elderly
- Post-infectious neutropenia, most commonly in children after viral infections (particularly varicella, measles, rubella, influenza, hepatitis, EBV, or HIV)
  - EBV and HIV can sometimes cause prolonged neutropenia; the rest are self-limited
- Bacterial infections, including Brucella, Rickettsiae, and mycobacteria
Drug-induced neutropenia, including agranulocytosis or more mild neutropenia
Autoimmune
- Primary: typically in patients less than 1 year old, can be severe, but usually resolves within 2 years
  - Needs prophylactic antibiotics and GCSF
- Secondary: usually mild, in the context of a systemic autoimmune disease (with lupus being common and tends to reflect disease activity)
- Felty syndrome (triad of rheumatoid arthritis, splenomegaly, and neutropenia)
Malignancy
- Acute leukemia
- Myelodysplastic syndrome
- LGL leukemia: associated with rheumatoid arthritis and can present as a Felty syndrome
- Myeloma
- Lymphoma
- Myelophthisic process
Dietary
- Vitamin B12 deficiency
- Folate deficiency
- Copper deficiency
- Global caloric malnutrition, including anorexia nervosa
Chronic idiopathic neutropenia