USMLE (Fach) / Hematology and Oncology (Lektion)
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- Platelet disorders Defects in platelet plug formation --> ↑ bleeding time (BT) Platelet abnormalities --> microhemorrhage: mucous membrane bleeding, epistaxis, petechiae, purpura, ↑ bleeding time, possibly decreased ...
- Bernard-Soulier syndrome Defect in platelet plug formation. Large platelets.↓ GpIb → defect in platelet-to-vWF adhesion. Abnormal ristocetin test that does not correct with mixing studies. Platelet count (PC): -/↓Bleeding ...
- Glanzmann thrombasthenia Defect in platelet integrin αIIbβ3 (GpIIb/IIIa) → defect in platelet-to-platelet aggregation, and therefore platelet plug formation. Labs: Blood smear shows no platelet clumping. Platelet count (PC): ...
- Hemolytic-uremic syndrome Characterized by thrombocytopenia, microangiopathic hemolytic anemia, and acute renal failure. - Typical HUS is seen in children, accompanied by diarrhea and commonly caused by Shiga toxin of enterohemorrhagic ...
- Immune thrombocytopenia Anti-GpIIb/IIIa antibodies → splenic macrophage consumption of platelet-antibody complex.May be 1° (idiopathic) or 2° to autoimmune disorder, viral illness, malignancy, or drug reaction. Labs: ↑ ...
- Thrombotic thrombocytopenic purpura Inhibition or deficiency of ADAMTS 13 (vWF metalloprotease) → ↓ degradation of vWF multimers. Pathogenesis: ↑ large vWF multimers → ↑ platelet adhesion → ↑ platelet aggregation and thrombosis. ...
- von Willebrand disease Intrinsic pathway coagulation defect: ↓ vWF → ↑ PTT (vWF acts to carry/protect factor VIII). Defect in platelet plug formation: ↓ vWF → defect in platelet-to-vWF adhesion. - Autosomal dominant. ...
- Disseminated intravascular coagulation Widespread activation of clotting → deficiency in clotting factors → bleeding state. Causes:- Sepsis (gram ⊝)- Trauma- Obstetric complications- Acute pancreatitis- Malignancy- Nephrotic syndrome- ...
- Factor V Leiden Production of mutant factor V (G → A DNA point mutation → Arg506Gln mutation near the cleavage site) that is resistant to degradation by activated protein C. Most common cause of inherited hypercoagulability ...
- Protein C or S deficiency ↓ ability to inactivate factors Va and VIIIa. ↑ risk of thrombotic skin necrosis with hemorrhage after administration of warfarin.
- Blood transfusion therapy Packed RBCs: ↑ Hb and O2 carrying capacity.- Use: acute blood loss, severe anemia Platelets: ↑ platelet count (↑ ~5000/mm3/unit)- Use: Stop significant bleeding (thrombocytopenia, qualitative ...
- Leukemia vs. lymphoma Leukemia:- Lymphoid or myeloid neoplasm with widespread involvement of bone marrow.- Tumor cells are usually found in peripheral blood. Lymphoma:- Discrete tumor mass arising from lymph nodes. Presentations ...
- Reed-Sternberg cells Distinctive tumor giant cell seen in Hodgkin lymphoma - binucleate or bilobed with the 2 halves as mirror images ("owl eyes") - RS cells are CD15+ and CD30+ B-cell origin
- Burkitt lymphoma Non-Hodgkin lymphoma- Occurs in adolescents or young adults - t(8;14) translocation of c-myc and heavy-chain Ig - "Starry sky" appearance, sheets of lymphocytes with interspersed "tingible body" macrophages- ...
- Diffuse large B-cell lymphoma - Occurs in older adults, but 20% in children - Alterations in Bcl-2, Bcl-6 - Most common type of non-Hodgkin lymphoma in adults
- Follicular lymphoma Non-Hodgkin lymphoma- Occurs in adults - t(14;18) – translocation of Ig and BCL-2 - Indolent course; Bcl-2- inhibits apoptosis- Presents with painless "waxing and waning" lymphadenopathy
- Mantle cell lymphoma Non-Hodgkin lymphoma- Occurs in adult males - t(11;14) – translocation of cyclin D1 and heavy-chain Ig, CD5+ - Very aggressive- Patients typically present with late-stage disease
- Adult T-cell lymphoma - Occurs in adults - Caused by HTLV (associated with IV drug abuse) - Adults present with cutaneous lesions- Especially affects populations in Japan, West Africa, the Caribbean - Lytic bone lesions, hypercalemia ...
- Mycosis fungoides/Sézary syndrome T-cell non-Hodgkin lymphoma- Occurs in adults Mycosis fungoides: - Skin patches/plaques (cutaneous T-cell lymphoma)- Characterized by atypical CD4+ cells with "cerebriform" nuclei and intraepidermal neoplastic ...
- Multiple myeloma Monoclonal plasma cell ("fried egg" appearance) cancer that arises in the marrow and produces large amounts of IgG (55%) or IgA (25%). - Bone marrow >10% monoclonal plasma cells.- Most common 1° tumor ...
- Myelodysplastic syndromes Stem-cell disorders involving ineffective hematopoiesis → defects in cell maturation of nonlymphoid lineages. Caused by de novo mutations or environmental exposure (eg, radiation, benzene, chemotherapy). ...
- Leukemias Unregulated growth and differentiation of WBCs in bone marrow → marrow failure → anemia (↓ RBCs), infections (↓ mature WBCs), and hemorrhage (↓ platelets). Usually presents with ↑ circulating ...
- Acute lymphoblastic leukemia/lymphoma Most frequently occurs in children; less common in adults (worse prognosis).- T-cell ALL can present as mediastinal mass (presenting as SVC-like syndrome).- Associated with Down syndrome. - Peripheral ...
- Chronic lymphocytic leukemia/small lymphocytic lymphoma ... Age: >60 years. Most common adult leukemia. - CD20+, CD23+, CD5+ B-cell neoplasm. - Often asymptomatic, progresses slowly- Smudge cells in peripheral blood smear- Autoimmune hemolytic anemia Richter transformation – ...
- Hairy cell leukemia Mature B-cell tumor.- Most commonly in adult males. - Cells have filamentous, hair-like projections (fuzzy appearing on LM).- Peripheral lymphadenopathy is uncommon. - Causes marrow fibrosis → dry tap ...
- Acute myelogenous leukemia Median onset 65 years. - Auer rods; myeloperoxidase ⊕ cytoplasmic inclusions seen mostly in APL (formerly M3 AML)- ↑↑↑ circulating myeloblasts on peripheral smear; adults. Risk factors: prior ...
- Chronic myelogenous leukemia - Occurs across the age spectrum with peak incidence 45-85 years, median age at diagnosis 64 years.- Defined by the Philadelphia chromosome (t[9;22], BCR-ABL) and myeloid stem cell proliferation. - Presents ...
- Langerhans cell histiocytosis Collective group of proliferative disorders of dendritic (Langerhans) cells. - Children, peak incidence 5-10 years Presentation:- Lytic bone lesions (mostly skull)→ Can cause recurrent otitis media ...
- Polycythemia vera Chronic myeloproliferative disorder of a ↑ hematocrit. - May present as intense itching after hot shower. - Rare but classic symptom is erythromelalgia (severe, burning pain and red-blue coloration) ...
- Essential thrombocythemia Chronic myeloproliferative disorder, characterized by massive proliferation of megakaryocytes and platelets. - Symptoms include bleeding and thrombosis.- Erythromelalgia may occur (headache, visual ...
- Myelofibrosis Chronic myeloproliferative disorder.Obliteration of bone marrow with fibrosis due to ↑ fibroblast activity. - Often associated with massive splenomegaly and "teardrop" RBCs. - ↓ RBCs, variable WBCs ...
- Chromosomal translocations t(8;14): Burkitt lymphoma (c-myc activation) t(9;22) (Philadelphia chromosome): CML, rarely ALL t(11;14): Mantle cell lymphoma (cyclin D1 activation) t(14;18): Follicular lymphoma (BCL-2 activation) ...
- Hodgkin lymphoma - Constitutional ("B") symptoms: low-grade fever, night sweats, weight loss- Localized, single group of nodes- Contiguous spread (stage is strongest predictor of prognosis)- Characterized by Reed-Sternberg ...
- Waldenström macroglobulinemia B-lymphocyte lymphoproliferative disorder with high levels of IgM - hyperviscosity syndrome (eg, blurred vision, Raynaud phenomenon, vertigo) - bone marrow biopsy reveals infiltrates of lymphocytes, ...
- Hemoglobin C disease Single nucleotide change in a codon causes lysine (basic) to replace normal glutamic acid (acidic) at beta 6 position. - Normochromic-normocytic anemia- Splenomegaly- Target cells- Rod-shaped crystals ...
- Erythrocytes - Carry O2 to tissues and CO2 to lungs. - Anucleate and lack organelles; biconcave, with large surface area-to-volume ratio for rapid gas exchange.- Life span of 120 days- Source of energy is glucose ...
- Leukocytes Divided into granulocytes (neutrophils, eosinophils, basophils, mast cells) and mononuclear cells (monocytes, lymphocytes). WBC differential count from highest to lowest:- Neutrophils (~60%)- Lymphocytes ...
- Monocytes Found in blood, differentiate into macrophages in tissues. Large, kidney-shaped nucleus. Extensive "frosted glass" cytoplasm.
- Plasma cell Produce large amounts of antibody specific to a particular antigen. - "Clock-face" chromatin distribution and eccentric nucleus, abundant RER, and well-developed Golgi apparatus. - Found in bone marrow ...
- Fetal erythropoiesis Fetal erythropoeisis occurs in:- Yolk sac (3-8 weeks)- Liver (6 weeks-birth)- Spleen (10-28 weeks)- Bone marrow (18 weeks to adult) Embryonic globins: ζ and ε.Fetal hemoglobin (HbF) = α2γ2Adult hemoglobin ...
- Rh hemolytic disease of the newborn Rh ⊝ mothers; Rh ⊕ fetus - First pregnancy: morther exposed to fetal blood (often during delivery) → formation of maternal anti-D IgG. Subsequent pregnancies: anti-D IgG crosses the placenta → ...
- Hemoglobin electrophoresis On a gel, hemoglobin migrates from the negatively charged cathode to the positively charged anode. HbA migrates the farthest, followed by HbF, HbS and HbC.This is because the missense mutations in HbS ...
- Procoagulation Oxidized vitamin K → Reduced vitamin K (epoxide reductase)Reduced vitamin K acts as a cofactor of γ-glutamyl carboxylase to activate coagulation factors. Vitamin K deficiency: ↓ synthesis of factors ...
- Anticoagulation Protein C –(thrombin-thrombomodulin complex in endothelial cells)→ activated protein CActivated protein C –(Protein S)→ cleaves and inactivates Va, VIIIa Plasminogen –(tPA)→ plasmin → ...
- Platelet plug formation (primary hemostasis) 1. Injury- Endothelial damage → transient vasoconstriction via neural stimulation reflex and endothelin (released from damaged cell)2. Exposure- vWF binds to exposed collagen- vWF is from Weibel-Palade ...
- Thrombogenesis Formation of insoluble fibrin mesh. - Aspirin irreversibly inhibits cyclooxygenase-1, thereby inhibiting TXA2 synthesis.- Clopidogrel, prasugrel, and ticlopidine inhibit ADP-induced expression of GpIIb/IIIa ...
- Iron deficiency ↓ iron due to chronic bleeding (eg, GI loss, menorrhagia), malnutrition, absorption disorders, GI surgery (eg, gastrectomy) or ↑ demand (eg, pregnancy) → ↓ final step in heme synthesis. Labs: - ↓ ...
- Megaloblastic anemia Impaired DNA synthesis → maturation of nucleus of precursor cells in bone marrow delayed relative to maturation of cytoplasm. RBC macrocytosis, hypersegmented neutrophils, glossitis. - Folate deficiency- ...
- Nonmegaloblastic anemia Macrocytic anemia in which DNA synthesis is unimpaired. Causes: alcoholism, liver disease RBC macrocytosis without hypersegmented neutrophils. Diamond-Blackfan anemia – Rapid-onset anemia within 1st ...
- HbC disease Glutamic acid-to-lysine mutation in β-globin. Causes extravascular hemolysis. Patients with HbSC (1 of each mutant gene) have milder disease than HbSS patients. Blood smear in homozygotes: hemoglobin ...