White blood cell disorders

White blood cell disorders

White blood cell disorders

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WBC Basics - The Body's First Responders

  • Function: Key mediators of inflammation and the immune response.
  • Normal Range: 4,000-11,000/μL.
    • Leukocytosis: >11,000/μL (indicates infection, stress, or inflammation).
    • Leukopenia: <4,000/μL (suggests immunosuppression, marrow failure).
  • Differential Count:
    • 📌 Mnemonic (most to least abundant): Never Let Monkeys Eat Bananas (Neutrophils, Lymphocytes, Monocytes, Eosinophils, Basophils).
  • Absolute Neutrophil Count (ANC):
    • $ANC = \text{WBC Count} \times (% \text{Neutrophils} + % \text{Bands})$.
    • Severe Neutropenia: ANC <500/μL; high risk for life-threatening infections.

⭐ A "left shift" indicates an acute inflammatory response (esp. bacterial infection), characterized by the premature release of immature neutrophils (e.g., bands, metamyelocytes) from the bone marrow.

Neutrophil Maturation: Myelocyte to Segmented Neutrophil

Myeloid Neoplasms - Precursor Pandemonium

  • Clonal hematopoietic stem cell disorders causing overproduction of one or more myeloid lineages. Spectrum ranges from ineffective hematopoiesis (MDS) to hyper-proliferation (MPN) to acute leukemia (AML).
  • Myelodysplastic Syndromes (MDS): Pancytopenia despite hypercellular marrow. Risk of AML transformation.
  • Myeloproliferative Neoplasms (MPN):
    • CML: BCR-ABL fusion gene.
    • Polycythemia Vera, Essential Thrombocythemia, Primary Myelofibrosis: Primarily JAK2, CALR, MPL mutations.

Auer Rods, eosinophilic needle-like inclusions in cytoplasm, are pathognomonic for Acute Myeloid Leukemia (AML).

Auer rods in acute myeloid leukemia blood smear

Lymphoid Leukemias - Clonal Chaos Crew

  • Acute Lymphoblastic Leukemia (ALL):
    • Most common childhood malignancy; blasts are TdT+.
    • B-ALL: CD10+, CD19+, CD20+. Good prognosis with t(12;21).
    • T-ALL: Can present as a mediastinal mass in a teenager.
  • Chronic Lymphocytic Leukemia (CLL):
    • Affects adults > 60; often asymptomatic with lymphocytosis.
    • Key finding: Smudge cells on peripheral smear.
    • Co-expression of CD5 and CD20.
    • Can undergo Richter transformation to an aggressive lymphoma.
  • Hairy Cell Leukemia:
    • Affects older males; cells have fine, hair-like projections.
    • Stains TRAP+ (Tartrate-Resistant Acid Phosphatase).
    • Causes massive splenomegaly and pancytopenia.

⭐ In CLL, smudge cells are fragile neoplastic lymphocytes crushed during peripheral blood smear preparation. Their presence is characteristic but not pathognomonic.

CLL peripheral blood smear with smudge cells and lymphocytes

Plasma Cell Dyscrasias - M-Protein Mayhem

  • Multiple Myeloma (MM): Malignant plasma cells producing monoclonal Ig (IgG > IgA).
    • 📌 CRAB criteria:Calcium (>11 mg/dL), Renal insufficiency, Anemia, lytic Bone lesions.
    • Labs: M-spike on SPEP, Bence-Jones proteinuria, Rouleaux formation (RBC stacks).
  • Waldenström Macroglobulinemia: IgM M-spike leading to hyperviscosity syndrome (blurry vision, Raynaud).
  • MGUS (Monoclonal Gammopathy of Undetermined Significance): Asymptomatic; precursor with risk of progression.

⭐ Multiple Myeloma is the most common primary malignant bone tumor in adults.

Multiple Myeloma in Bone Marrow Biopsy

High‑Yield Points - ⚡ Biggest Takeaways

  • Leukemoid reaction is distinguished from CML by a high LAP score; CML has a low LAP score and the Philadelphia chromosome (t(9;22)).
  • Acute leukemias (ALL, AML) show >20% blasts in the marrow; Auer rods are pathognomonic for AML.
  • CLL is characterized by smudge cells and lymphadenopathy in the elderly.
  • Hodgkin lymphoma is identified by Reed-Sternberg cells and typically spreads contiguously.
  • Multiple myeloma presents with CRAB findings (hypercalcemia, renal failure, anemia, bone lesions) and an M-spike.

Practice Questions: White blood cell disorders

Test your understanding with these related questions

A 61-year-old woman presents to her primary care physician for a routine check-up. Physical examination demonstrates asymmetric peripheral neuropathy in her feet. The patient has no previous relevant history and denies any symptoms of diabetes. Routine blood work shows normal results, and she is referred to a hematologist. Subsequent serum protein electrophoresis demonstrates a slightly elevated gamma globulin level, and monoclonal gammopathy of undetermined significance is diagnosed. Which of the following diseases is most likely to develop over the course of this patient’s condition?

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Flashcards: White blood cell disorders

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The t(9;22) translocation (BCR-ABL) is also known as the _____ chromosome

TAP TO REVEAL ANSWER

The t(9;22) translocation (BCR-ABL) is also known as the _____ chromosome

Philadelphia

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