White Blood Cell Disorders

White Blood Cell Disorders

White Blood Cell Disorders

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WBC Overview - Count Control

  • WBC production (leukopoiesis) regulated by growth factors (e.g., G-CSF) & cytokines, responding to stimuli (infection).

  • Normal WBC Counts & Differentials (Approximate Ranges in Children):

    AgeTotal WBC (x10³/µL)Neutrophils (%)Lymphocytes (%)
    Newborn9-3040-8020-40
    1-12 mo6-17.520-4545-70
    1-6 yr5-15.525-6035-65
    >6 yr4.5-13.535-7025-50
  • Key Definitions: (ANC: Absolute Neutrophil Count)

    • Leukocytosis: ↑ WBC count (age-specific).
    • Leukopenia: ↓ WBC count (age-specific).
    • Neutrophilia: ↑ ANC (age-specific).
    • Neutropenia: ANC < 1500/µL (Mild: 1000-1500; Moderate: 500-999; Severe: < 500/µL).
    • Lymphocytosis: ↑ Lymphocytes (age-specific).
    • Lymphopenia: ↓ Lymphocytes (age-specific).
    • Eosinophilia: Eosinophils > 500/µL.

⭐ Age-related variations in WBC counts are crucial; lymphocyte predominance is normal in early childhood (up to 4-6 years), shifting to neutrophil predominance later.

Pediatric Normal WBC Counts and Differential by Age

Neutrophil Disorders - Neutro-Navigators

  • Neutropenia: Absolute Neutrophil Count (ANC) < 1500/µL; severe if ANC < 500/µL.
    • Causes: Congenital (e.g., Kostmann syndrome, cyclic neutropenia); acquired (e.g., drugs, infections, autoimmune).
  • Neutrophilia: Increased neutrophils.
    • Causes: Infections, inflammation, stress.
  • Functional Neutrophil Disorders:
    • Chronic Granulomatous Disease (CGD): Defect in NADPH oxidase. Recurrent infections with catalase-positive organisms (📌 e.g., S. aureus, Aspergillus, Serratia). Diagnosis: Dihydrorhodamine (DHR) test or Nitroblue Tetrazolium (NBT) test.
    • Leukocyte Adhesion Deficiency (LAD): Types I, II, III. Delayed umbilical cord separation, recurrent non-purulent bacterial infections.

⭐ Chronic Granulomatous Disease (CGD) is most commonly X-linked recessive and diagnosed by an abnormal dihydrorhodamine (DHR) flow cytometry test or nitroblue tetrazolium (NBT) dye test, showing impaired phagocytic oxidative burst.

Neutrophil function and related disorders

Lymphocyte Disorders - Lympho-Legends

  • Lymphocytosis: ↑ Lymphocytes
    • Definition: Age-dependent. Infants >9000/µL, older children >7000/µL.
    • Causes:
      • Viral: Infectious Mononucleosis (EBV, CMV) - Downey cells (atypical lymphocytes).
      • Bacterial: Pertussis (marked ↑, normal morphology), TB.
      • Malignancies: Acute Lymphoblastic Leukemia (ALL).
  • Lymphopenia: ↓ Lymphocytes
    • Definition: Age-dependent. Older children <1500/µL.
    • Causes: Immunodeficiencies (SCID, DiGeorge), HIV, drugs, malnutrition.
  • Severe Combined Immunodeficiency (SCID):
    • Presentation: Failure to thrive (FTT), recurrent severe infections, absent thymic shadow.
    • Key Types: X-linked, ADA deficiency. Atypical lymphocytes (Downey cells) in peripheral smear

⭐ Infectious Mononucleosis (caused by EBV) is characterized by fever, pharyngitis, posterior cervical lymphadenopathy, splenomegaly, and atypical T lymphocytes (Downey cells) on the peripheral blood smear.

Eosinophil & Other Disorders - Eosino-Enigmas

  • Eosinophilia: Absolute eosinophil count >500/µL.
    • Causes 📌 NAACP: Neoplasm, Allergy/Asthma, Addison's disease, Collagen vascular diseases, Parasitic infections.
    • Hypereosinophilic Syndrome (HES): Persistent eosinophilia >1500/µL with end-organ damage. Peripheral blood smear with eosinophilia
  • Monocyte Disorders:
    • Monocytosis: ↑ monocytes. Causes: Chronic infections (e.g., TB), IBD, malignancies.
    • Langerhans Cell Histiocytosis (LCH): Rare, clonal proliferation of Langerhans cells; can affect bone, skin.
  • Basophil Disorders:
    • Basophilia: ↑ basophils. Rare. Causes: CML, allergic reactions, hypothyroidism.

⭐ The mnemonic 'NAACP' (Neoplasm, Allergy/Asthma, Addison's disease, Collagen vascular diseases, Parasites) is a useful tool for remembering the common causes of eosinophilia in children.

High‑Yield Points - ⚡ Biggest Takeaways

  • Neutropenia: ANC < 1500/µL (severe < 500/µL). Kostmann syndrome (SCN) ↑ AML risk.
  • LAD-1: CD18 defect, delayed cord separation, recurrent non-purulent infections, marked neutrophilia.
  • Chédiak-Higashi: AR; partial albinism, recurrent infections, giant granules in WBCs.
  • CGD: Defective NADPH oxidase, recurrent catalase-positive infections. DHR/NBT test.
  • EBV (Mononucleosis): Fever, pharyngitis, lymphadenopathy, atypical lymphocytes (Downey cells).
  • ALL: Most common childhood cancer; lymphoblasts in blood/marrow, pancytopenia.

Practice Questions: White Blood Cell Disorders

Test your understanding with these related questions

An 80-year-old asymptomatic man presents with a total leukocyte count of 100,000, with 80% lymphocytes and 20% PMCs. What is the most probable diagnosis?

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Flashcards: White Blood Cell Disorders

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Patients with -thalassemia major are at risk of _____ with parvovirus B19 infection of erythroid precursors

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Patients with -thalassemia major are at risk of _____ with parvovirus B19 infection of erythroid precursors

aplastic crisis

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