II. Definitions

  1. Leukocytosis
    1. White Blood Cell Count over 11,000/mm3 (non-pregnant adults)
    2. See White Blood Cell Count for normal White Blood Cell ranges based on age, pregnancy
  2. Leukemoid Reaction
    1. White Blood Cell Count 50,000 to 100,000/mm3
    2. Caused by serious infections (C. Diff, Sepsis), solid tumor, organ rejection
  3. Severe Leukocytosis (Hyperleukocytosis)
    1. White Blood Cell Count >100,000/mm3
    2. Associated with Leukemia or myeloproliferative disorder
    3. May be associated with Leukostasis (Hyperviscosity Syndrome) in AML (or CML in Blast Crisis)

III. Causes: Cell line specific causes

  1. See Neutrophilia (most common cause)
  2. See Lymphocytosis
  3. See Monocytosis
  4. See Eosinophilia (rarely causes Leukocytosis)

IV. Causes: Benign Syndromes

  1. Leukemoid Reaction
    1. WBC Count exceeds 50,000
    2. Cause not involving Bone Marrow
    3. Usually due to non-malignant cause
  2. Reactive Leukocytosis
    1. Fever
    2. Focal infectious signs
    3. Normal Platelet Count and Hemoglobin

V. Causes: Malignancy

  1. Acute Leukemia
    1. Thrombocytopenia
    2. Peripheral Smear with many immature cells (blasts)
    3. Marrow hypercellular with >30% blast cells
    4. Hyperuricemia
  2. Chronic Leukemia
    1. Normal Platelet Count and Hemoglobin

VI. Red Flags: Signs of Hematologic Malignancies or other Bone Marrow disorders

  1. History
    1. Bruising or Bleeding Diathesis
    2. Fatigue or weakness
    3. Fever >100.4 F (38 C)
    4. Night Sweats
    5. Unintentional Weight Loss
    6. Immunosuppression
  2. Exam
    1. Lymphadenopathy
    2. Bleeding, Ecchymosis, or Petechiae
    3. Lethargy
    4. Splenomegaly or Hepatomegaly
  3. Labs
    1. Anemia (reduced RBC Count or decreased Hemoglobin or Hematocrit)
    2. Thrombocytopenia or Thrombocytosis
    3. Peripheral Blood Smear abnormalities (monomorphic Lymphocytosis, immature cells)
    4. White Blood Cell Count >30,000/mm3 (or >20,000/mm3 after initial management)
      1. WBC Count >100,000/mm3 indicates urgent hematology consult
  4. References
    1. Racil (2011) Am J Hematol 86(9): 800-3 [PubMed]

VII. Evaluation: Leukocytosis

  1. Step 1
    1. Complete Blood Count with Platelets
      1. Confirm persistent WBC Count >11,000/mm3
    2. Consider known causes
      1. See WBC Count for normal ranges (increased in childhood, pregnancy)
      2. See specific WBC cell line increases (Neutrophilia, Lymphocytosis...)
  2. Step 2: Consider malignancy
    1. See Red Flags for Hematologic Malignancy as above
    2. Malignancy suspected
      1. Hematology-Oncology Consultation
      2. Peripheral Blood Smear
    3. Additional tests typically ordered by hematoology
      1. Bone Marrow Aspiration (critical in Acute Leukemia)
      2. Flow cytometry, cytogenic tests, molecular tests
  3. Step 3: Cell Line specific approach
    1. Neutrophilia (Neutrophils >7000/mm3)
      1. See Neutrophilia for evaluation
    2. Lymphocytosis (Lymphocytes >4500/mm3)
      1. See Lymphocytosis for evaluation
    3. Monocytosis (Monocytes >880/mm3)
      1. See Monocytosis for evaluation
    4. Eosinophilia (Eosinophils >500/mm3)
      1. See Eosinophilia for evaluation
    5. Basophilia (Basophils >100/mm3)
      1. See Basophilia for causes
      2. Consider malignancy
      3. Consider allergic condition

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Related Studies

Ontology: Leukemoid Reaction (C0023501)

Definition (NCI) A hematology test result that indicates the presence of an increased white blood cell count and increased neutrophil precursors resembling leukemia, in a peripheral blood smear.
Definition (MSH) A peripheral blood picture resembling that of leukemia or indistinguishable from it on the basis of morphologic appearance alone. (Dorland, 27th ed)
Concepts Disease or Syndrome (T047)
MSH D007955
ICD9 288.62
ICD10 D72.823
SnomedCT 56478004
English Leukemoid Reaction, Leukemoid Reactions, Reactions, Leukemoid, LEUKAEMOID REACTION, LEUKEMOID REACTION, Reaction, Leukemoid, Leukemoid reactions, leukemoid reaction (diagnosis), leukemoid reaction, Reaction leukemoid, Leukemoid reaction NOS, Leukemoid Reaction [Disease/Finding], leukemoid reactions, Leukemoid reaction, Leukaemoid reaction, Leukemoid reaction (disorder), leukemoid; reaction, reaction; leukemoid, Leukemoid reaction, NOS
French REACTION LEUCEMOIDE, Etat pseudoleucémique, Leucemoïde, réaction, Réaction leucémoïde
German LEUKAEMOIDE REAKTION, Reaktion leukomoid, leukaemoide Reaktion, Leukämoide Reaktion
Dutch reactie leukemoïd, leukemoïd; reactie, reactie; leukemoïd, leukemoïde reactie, Leukemoïde reactie, Reactie, leukemoïde
Japanese 類白血病反応, ルイハッケツビョウハンノウ
Swedish Leukemoid reaktion
Czech leukemoidní reakce, Leukemoidní reakce
Finnish Leukemoidireaktio
Spanish LEUCEMOIDE, REACCION, reacción leucemoide (trastorno), reacción leucemoide, Reacción leucemoide, Reacción Leucemoide
Portuguese REACCAO LEUCEMOIDE, Reação Leucemoide, Reacção leucemóide
Polish Reakcja białaczkopodobna
Hungarian leukaemoid reakció, Leukemoid reakció
Norwegian Leukemoid reaction
Italian Reazione leucemoide

Ontology: Leukocytosis (C0023518)

Definition (MSH) A transient increase in the number of leukocytes in a body fluid.
Definition (CSP) transient increase in the number of leukocytes in a body fluid.
Concepts Pathologic Function (T046)
MSH D007964
ICD9 288.60
ICD10 D72.829
SnomedCT 154832004, 191368009, 267568006, 191364006, 142918008, 111583006
English Leukocytoses, LEUKOCYTOSIS, Leukocytosis, unspecified, leukocytosis (diagnosis), leukocytosis, Leucocytosis NOS, Leukocytosis, Leukocytosis NOS, Leukocytosis [Disease/Finding], leucocytosis, leukocytoses, Leucocytosis (finding), Disorder characterized by leukocytosis, Leucocytosis, Leukocytosis (disorder), Leucocytosis, NOS, Leukocytosis, NOS
French LEUCOCYTOSE, Leucocytose SAI, Leucocytose, Hyperleucocytose
Portuguese LEUCOCITOSE, Leuocitose NE, Leucocitose
Spanish LEUCOCITOSIS, Leucocitosis NEOM, leucocitosis (trastorno), leucocitosis, Leucocitosis
German LEUKOZYTOSE, Leukozytose NNB, Leukozytose
Dutch leukocytose NAO, leukocytose, Leukocytose
Italian Leucocitosi NAS, Leucocitosi
Japanese 白血球増加症NOS, 白血球増加症, ハッケッキュウゾウカショウNOS, ハッケッキュウゾウカショウ
Swedish Leukocytos
Czech leukocytóza, Leukocytóza, Leukocytóza NOS
Finnish Leukosytoosi
Croatian Not Translated[Leukocytosis]
Polish Leukocytoza
Hungarian leukocytosis, Leukocytosis k.m.n.
Norwegian Leukocytose, Økt mengde hvite blodceller