Neutropenia is defined as a reduction in the absolute neutrophil count (ANC) below 1,500 cells/μL in adults and children over 1 year — a threshold that marks the point at which the body’s primary first-line defense against bacterial and fungal pathogens becomes meaningfully compromised. Neutrophils (also called polymorphonuclear cells/PMNs, polys, segs, or granulocytes) constitute 50-70% of all circulating white blood cells and are the immune system’s frontline rapid-responders: they are the first cells recruited to sites of infection, where they phagocytize bacteria, release antimicrobial enzymes, and form neutrophil extracellular traps (NETs); their loss therefore creates a state of profound immune vulnerability that is quantitatively proportional to the depth and duration of the ANC nadir. Neutropenia is classified by severity as mild (ANC 1000-1499), moderate (ANC 500-999), severe (ANC <500), and agranulocytosis (ANC <100/200) — the last two categories representing true medical emergencies; it is further classified by mechanism as decreased production (chemotherapy-induced, aplastic anemia, congenital, nutritional deficiency), increased peripheral destruction (autoimmune, hypersplenism, drug-mediated immune destruction), or increased margination/sequestration (sepsis, hemodialysis). The most clinically significant complication is febrile neutropenia (FN) — defined as ANC <500 + single oral temp ≥38.3°C (101°F) or ≥38°C (100.4°F) sustained for ≥1 hour — which is an oncologic emergency requiring immediate hospitalization, blood cultures, and empiric broad-spectrum antibiotics, as ~50% of FN patients have an occult infection and 20% of profoundly neutropenic patients develop bacteremia.
"Neither (acid nor base)” — neutrophils are named for their neutral staining with standard H&E dyes (neither the acidophilic eosin of eosinophils nor the basophilic dye of basophils)
“Poverty, deficiency, lack” (from penēs = poor person, one without means)
The PIE root behind penia is pen- — “to toil, to suffer” — conveying a state of deprivation or insufficiency. The suffix -penia is one of the most productive in hematology: it appears in thrombocytopenia (low platelets), leukopenia (low WBCs), erythropenia (low red cells), pancytopenia (low all cell lines), sarcopenia (low muscle mass), and osteopenia (low bone density). The root neutro- was adopted into the cell name by Ehrlich in the 1870s when he developed polychrome staining and noted that the granules of this WBC subtype took up neither acid nor basic stains exclusively. The compound neutropenia as a clinical term entered standard medical usage in the early 20th century as differential WBC counting became routine laboratory practice.
🔀 ALIASES / ALTERNATE TERMS
Agranulocytosis(extreme neutropenia: ANC <100-200/μL; near-complete absence of granulocytes; coded D70.9 when unspecified or by etiology-specific subcode)
Granulocytopenia(older synonym; encompasses all granulocyte types; often used interchangeably with neutropenia in older literature)
Benign ethnic neutropenia (BEN)(lower baseline ANC in individuals of African, Middle Eastern, or Yemenite Jewish descent; not pathologic; D70.9 if coded)
Decreased ANC(ICD-10-CM tabular includes language; synonym used in lab reporting)
ANC nadir(clinical term for the lowest point of neutrophil count post-chemotherapy, typically days 7-14)
🔗 RELATED TERMS
absolute neutrophil count (ANC) — calculated as WBC × (% segs + % bands); the defining lab value; normal 1500-8000/μL
leukopenia — broader reduction in total WBCs (<4000/μL); neutropenia is the most clinically significant subset; D72.819
pancytopenia — reduction in all three cell lines (RBC, WBC, platelets); D61.818
Subsequent hospital inpatient care, moderate-high complexity
⚠️ Coding Note:D70.1 (chemotherapy-induced neutropenia) is one of the most frequently coded hematology diagnoses on inpatient oncology/hematology floors — and it carries a specific ICD-10-CM instructional note to use additional code for adverse effect (T45.1X5A for initial encounter). For febrile neutropenia, always pair D70.x with R50.81 — the combination is what many clinical documentation integrity (CDI) and quality programs track as a key complication. Sequencing critical rule: when neutropenic sepsis is documented (FN + organ dysfunction), the sepsis code sequences FIRST (A41.xx) with neutropenia (D70.x) as a secondary code — do NOT let neutropenia lead when sepsis is established. For mucositis co-occurring with neutropenia, ICD-10-CM has explicit “use additional code” instructions in the D70 block: always capture K12.3 (oral), K92.81 (GI), or the appropriate site-specific mucositis code when documented, as this is a HAC/complication driver and supports medical necessity for prolonged stays. D70.1 vs D70.2: D70.1 is specifically chemo-drug neutropenia; D70.2 is all other drug-induced causes — clozapine, propylthiouracil, antithyroid agents, chloramphenicol, and some antibiotics are common D70.2 triggers. G-CSF billing (J1440/J2505): HCPCS billing requires documented ANC levels and clinical indication; Medicare LCD L37176 governs coverage criteria — the neutropenia code must support medical necessity in the record.
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