Blood dyscarias
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Fig. 14.7 - Sickle cell disease (peripheral blood smear): (A) Low magnification - irreversibly sickled cells, target cells, anisocytosis, poikilocytosis. (B) High magnification - an irreversibly sickled cell at center.
II. WHITE CELL DISORDERS / NEOPLASTIC DISEASES
Leukemias and Lymphomas - Overview
White cell neoplasms are classified by:
- Cell of origin - myeloid vs. lymphoid lineage
- Clinical behavior - acute (immature blasts) vs. chronic (mature cells)
- Site of predominance - bone marrow/blood (leukemia) vs. lymph nodes/solid tissue (lymphoma)
| Leukemia Type | Cell of Origin | Key Features |
|---|---|---|
| Acute Myeloid Leukemia (AML) | Myeloid precursors | Auer rods, myeloperoxidase+, most common acute leukemia in adults |
| Acute Lymphoblastic Leukemia (ALL) | Lymphoid precursors | Most common leukemia in children; TdT+; good prognosis in children |
| Chronic Myelogenous Leukemia (CML) | Myeloid stem cell | Philadelphia chromosome t(9;22), BCR-ABL fusion; treated with imatinib |
| Chronic Lymphocytic Leukemia (CLL) | Mature B cells | Most common leukemia in adults in Western world; smudge cells |
Lymphomas
| Type | Key Features |
|---|---|
| Hodgkin Lymphoma (HL) | Reed-Sternberg cells ("owl-eye" bilobed nuclei); EBV association; bimodal age distribution |
| Non-Hodgkin Lymphoma (NHL) | Heterogeneous group; follicular (indolent) vs. diffuse large B-cell (aggressive) |
| Multiple Myeloma | Plasma cell dyscrasia; lytic bone lesions, Bence Jones protein, CRAB criteria |
| Burkitt Lymphoma | t(8;14) MYC translocation; "starry-sky" pattern; associated with EBV |
Plasma Cell Dyscrasias
- Multiple Myeloma: Clonal proliferation of plasma cells in bone marrow; produces monoclonal immunoglobulin (M-protein)
- CRAB criteria: hyperCalcemia, Renal failure, Anemia, Bone lesions
- Bence Jones proteinuria (free light chains in urine)
- MGUS (Monoclonal Gammopathy of Undetermined Significance): Many patients have no serious underlying pathology, but a malignant plasma cell dyscrasia may eventually develop in some cases - Bradley and Daroff's Neurology in Clinical Practice
III. MYELOPROLIFERATIVE NEOPLASMS
These are clonal disorders of multipotent myeloid stem cells characterized by proliferation of one or more myeloid lineages:
| Disorder | Key Feature |
|---|---|
| Polycythemia Vera (PV) | JAK2 mutation; increased RBCs (and often WBCs/platelets); hyperviscosity; risk of thrombosis |
| Essential Thrombocythemia (ET) | JAK2 or CALR mutation; marked thrombocytosis; thrombosis and bleeding |
| Primary Myelofibrosis (PMF) | JAK2/CALR mutation; marrow fibrosis; extramedullary hematopoiesis; tear-drop cells |
| CML | BCR-ABL (Philadelphia chromosome) |
IV. PLATELET AND COAGULATION DISORDERS
Thrombocytopenias (Platelet Count <150,000/µL)
| Cause | Examples |
|---|---|
| Decreased production | Aplastic anemia, leukemia infiltrating marrow, myelodysplastic syndrome |
| Increased destruction - immune | ITP (Immune Thrombocytopenic Purpura) |
| Increased destruction - non-immune | TTP, HUS, DIC |
| Sequestration | Hypersplenism |
Coagulation Disorders
| Disorder | Mechanism | Lab Findings |
|---|---|---|
| Hemophilia A | Factor VIII deficiency (X-linked) | Prolonged aPTT, normal PT |
| Hemophilia B | Factor IX deficiency (X-linked) | Prolonged aPTT, normal PT |
| von Willebrand Disease | vWF deficiency/dysfunction | Prolonged bleeding time + aPTT |
| DIC | Widespread activation of coagulation | Prolonged PT + aPTT, low fibrinogen, elevated D-dimers, thrombocytopenia |
| Vitamin K deficiency | Deficiency of factors II, VII, IX, X | Prolonged PT > aPTT |
V. OTHER IMPORTANT BLOOD DYSCRASIAS
Aplastic Anemia
- Destruction or suppression of multipotent myeloid stem cells -> pancytopenia (anemia + leukopenia + thrombocytopenia)
- Causes: autoimmune (most common), radiation, benzene, chloramphenicol, drugs
- Bone marrow: hypocellular ("empty marrow"), replaced by fat
- Treatment: immunosuppression (anti-thymocyte globulin + cyclosporine) or allogeneic stem cell transplant
Myelodysplastic Syndromes (MDS)
- Clonal stem cell disorder with ineffective hematopoiesis and peripheral cytopenias
- Dysplastic changes in all three cell lines
- Risk of transformation to AML (~30%)
VI. KEY CLINICAL CORRELATIONS
Drug-Induced Blood Dyscrasias
Several drugs are notorious for causing blood dyscrasias:
- Clozapine (antipsychotic): Risk of life-threatening agranulocytosis/blood dyscrasia; requires mandatory CBC monitoring - Maudsley Prescribing Guidelines in Psychiatry
- Sulfinpyrazone: Associated with increased frequency of blood dyscrasias (NSAID-like) - Firestein & Kelley's Textbook of Rheumatology
- Chloramphenicol: Aplastic anemia
- Carbamazepine, phenytoin: Agranulocytosis, aplastic anemia
Blood Dyscrasia Presenting as Purpura / Cutaneous Signs
- Purpura on the skin implies an underlying blood dyscrasia (platelet/vascular problem) - Fitzpatrick's Dermatology
- Jaundice with purpura suggests concurrent hepatic pathology with coagulopathy
Ocular Manifestations
- Hyphema can result from blood dyscrasias or clotting disorders - Wills Eye Manual
Summary Table: Key Lab Findings in Blood Dyscrasias
| Condition | Hb/Hct | MCV | WBC | Platelets | Reticulocytes | Special Test |
|---|---|---|---|---|---|---|
| Iron deficiency anemia | Low | Low (microcytic) | Normal | Normal/High | Low | Low ferritin, low TIBC saturation |
| Megaloblastic anemia | Low | High (macrocytic) | Normal/Low | Normal/Low | Low | Low B12/folate, hypersegmented neutrophils |
| Hemolytic anemia | Low | Normal | Normal | Normal | High | + Coombs, elevated LDH/bilirubin |
| Aplastic anemia | Low | Normal | Low | Low | Low | Hypocellular bone marrow biopsy |
| AML/ALL | Low | Variable | Very high (blasts) | Low | Low | Blasts >20% in marrow |
| CML | Normal/Low | Normal | Very high (mature cells) | High | Normal | Philadelphia chromosome |
| Polycythemia vera | High | Normal | High | High | Normal | JAK2 mutation |
| ITP | Normal | Normal | Normal | Very low | Normal | Anti-platelet antibodies |
| DIC | Low | Normal | Variable | Low | Variable | Elevated D-dimers, low fibrinogen, prolonged PT+aPTT |
Sources:
- Robbins, Cotran & Kumar Pathologic Basis of Disease (primary classification and hematopathology)
- Goldman-Cecil Medicine International Edition
- Harrison's Principles of Internal Medicine 22E
- Bradley and Daroff's Neurology in Clinical Practice (plasma cell dyscrasias)
- Maudsley Prescribing Guidelines in Psychiatry (drug-induced dyscrasias)
- Fitzpatrick's Dermatology (cutaneous signs)
- Wills Eye Manual (ocular complications)
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