Definition

• • Extreme elevation of leukocyte count (>50,000/μL) composed of mature and/or immature neutrophils.

Causes

• 1. Infection (severe, chronic, e.g., tuberculosis), esp. in children;

  2. hemolysis (severe);

  3. malignant neoplasms (esp. carcinoma of the breast, lung, kidney);

  4. cytokines (e.g., G-CSF, GM-CSF).

May be distinguished from chronic myeloid leukemia (CML) by measurement of the leukocyte alkaline phosphatase (LAP) level: elevated in leukemoid reactions, depressed in CML.

Definition

• • Similar to leukemoid reaction (Extreme elevation of leukocyte count (>50,000/μL) composed of mature and/or immature neutrophils) + addition of nucleated RBCs and schistocytes on blood smear.

Causes

• 1. Myelophthisis—invasion of the bone marrow by tumor, fibrosis, granulomatous processes; smear shows “teardrop” RBCs;

  2. myelofibrosis—same pathophysiology as myelophthisis, but the fibrosis is a primary marrow disorder;

  3. hemorrhage or hemolysis (rarely, in severe cases)

Definition

• • Absolute basophil count >100/μL.

Causes

• 1. Allergic diseases

  2. myeloproliferative disorders (esp. CML)

  3. chronic inflammatory disorders (rarely).

Definition

• • Absolute eosinophil count >500/μL.

Causes

• 1. Drugs

  2. parasitic infections

  3. allergic diseases

  4. collagen vascular diseases

  5. malignant neoplasms

  6. hypereosinophilic syndromes.

Definition

• • Absolute lymphocyte count >5000/μL.

Causes

• 1. Infection—infectious mononucleosis, hepatitis, cytomegalovirus, rubella, pertussis, tuberculosis, brucellosis, syphilis;

  2. endocrine disorders—thyrotoxicosis, adrenal insufficiency;

  3. neoplasms—chronic lymphocytic leukemia (CLL), most common cause of lymphocyte count >10,000/μL.

Definition

• • Absolute monocyte count >800/μL.

Causes

• 1. Infection—subacute bacterial endocarditis, tuberculosis, brucellosis, rickettsial diseases (e.g., Rocky Mountain spotted fever), malaria, leishmaniasis;

  2. granulomatous diseases—sarcoidosis, Crohn’s disease;

  3. collagen vascular diseases— rheumatoid arthritis, systemic lupus erythematosus (SLE), polyarteritis nodosa, polymyositis, temporal arteritis;

  4. hematologic diseases—leukemias, lymphoma, myeloproliferative and myelodysplastic syndromes, hemolytic anemia, chronic idiopathic neutropenia;

  5. malignant neoplasms.

Definition

• • Absolute neutrophil count (polys and bands) >10,000/μL.

Pathophysiology

• • ↑ production

  • ↑ marrow mobilization

  • ↓ margination (adherence to vessel walls);

Causes

• • Exercise, stress;

  • infections—esp. bacterial; smear → ↑ numbers of immature neutrophils (“left shift”), toxic granulations, Döhle bodies;

  • burns;

  • tissue necrosis (e.g., myocardial, pulmonary, renal infarction);

  • chronic inflammatory disorders (e.g., gout, vasculitis);

  • drugs (e.g., glucocorticoids, epinephrine, lithium);

  • cytokines [e.g., granulocyte colony-stimulating factor (G-CSF), granulocyte-macrophage colony-stimulating factor (GM-CSF)];

  • myeloproliferative disorders;

  • metabolic (e.g., ketoacidosis, uremia);

  • other—malignant neoplasms, acute hemorrhage or hemolysis, after splenectomy.