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Path 14 RBC
Path 14 RBC Bleeding Disorders
| Question | Answer |
|---|---|
| causes of microcytic, hypochromic anemia (MCV<80)? | iron def; alpha- and beta-thalassemia; lead poisoning; sideroblastic anemia |
| causes of megaloblastic anemia? | folate deficiency; B12 deficiency |
| causes of nonhemolytic normocytic, normochromic anemia? | anemia of chronic dz; aplastic anemia; kidney dz |
| causes of intrinsic hemolytic anemia? | hereditary spherocytosis; G6PD def; pyruvate kinase def; SCA; HbC defect parxoysmal nocturnal hemoglobinuria |
| causes of extrinsic hemolytic anemia? | autoimmune; microangiopathic (eg DIC, TTP-HUS); infectious |
| causes of intravascular hemolysis? | paroxysmal nocturnal hemoglobinuria; autoimmune (cold agglutinins); mechanical (AO stenosis, prosthetic valve) |
| causes of extravascular hemolysis? | Hereditary spherocytosis; G6PD def; Pyruvate kinase def; SCA; HbC defect; Autoimmune (warm agglutintins); Microangiopathic (eg DIC, TTP-HUS) |
| Types of normochromic, normocytic anemias? | Nonhemolytic; Intrinsic hemolytic; Extrinsic hemolytic; Intravascular hemolysis Extravascular hemolysis |
| why does acute blood loss result in anemia? | blood volume lost is restored by intravascular shift of water from interstitial fluid compartment, resulting in hemodilution and lowering of HCT |
| What changes in peripheral blood are seen after significant blood loss? | low HCT; reticulocytosis; leukocytosis; thrombocytosis |
| which anemia is characterized by splenomegaly and jaundice? | extravascular hemolytic anemia |
| which anemia is manifested by hemoglobinemia, hemoglobinuria, hemosiderinuria, and jaundice? | intravascular hemolytic anemia |
| common non-hematologic complication of chronic hemolytic anemia | pigment gallstones |
| normocytic, normochromic anemia w/ reticulocytosis | hemolytic anemia |
| anemia resulting in hemosiderosis of spleen, liver, and bone marrow | hemolytic anemia |
| most prevalent inheritance pattern in spherocytosis? | autosomal dominant (75%) (25% have more severe form caused by two different defects) |
| PBS shows small, hyperchromic RBCs lacking central pallor. Dx? | spherocytosis |
| Howell-jolly bodies indicate what? | splenic dysfunction or splenectomy (esp in setting of spherocytosis) |
| what causes spherocytosis? | mutations lead to insufficiency of RBC membrane components and progressive loss of membrane fragments |
| what are the RBC membrane skeletal components? | ankyrin, band 3, spectrin, band 4.2 |
| what usually triggers aplastic crises in spherocytosis? | parvovirus infxn (kills RBC progenitors) |
| treatment for spherocytosis? | splenectomy and/or transfusion |
| CBC findings in spherocytosis? | anemia, inc MCHC, inc RDW |
| abnormalities in hexose monophosphate shunt or glutathione metabolism are the basis of what disease? | G6PD-deficiency (hemolysis) |
| inheritance pattern of G6PD-def? | X-linked (males at higher risk) |
| PBS shows RBCs with Heinz bodies and bite cells. Dx? | G6PD-def |
| what triggers hemolysis in G6PD-deficient patients? | oxidant stress, e.g. infxn, drugs (primaquine, chloroquine, sulfonamides), fava beans |
| in what diseases are Heinz bodies found? | G6PD-def, alpha thalassemia |
| what causes Heinz bodies? | exposure of RBC to high levels of oxidants cross-links globin chains which become denatured |
| what causes bite cells? | macrophages in splenic cords attempt to remove Heinz bodies and damage membrane |
| why is spherocytosis self limited? | only old RBCs are at risk for lysis |
| disease associated with a mutation that replaces glutamate in beta globin with valine | sickle cell disease |
| sickle cell trait vs. disease? | heterozygosity for HbS |
| composition of HbA? | alpha2beta2 |
| composition of HbA2? | alpha2 delta2 |
| composition of HbF? | alpha2 gamma2 |
| composition of HbS? | alpha2 beta(sickle)2 |
| what disorders confer immunity to malaria? | sickle cell trait, G6PD-deficiency |
| when does SCA start in child that has inherited the disease? | 6-7 mo (persistence of HbF) |
| what other disease, when coexistent with homozygous HbS, leads to milder disease? | a-thalassemia |
| "crew cut" skull x-ray from marrow expansion from inc erythropoiesis? | SCA and thalassemias |
| what precipitates sickling in SCA? | low O2 or RBC dehydration |
| complications in SCA homozygotes? | - aplastic crisis (B19 infxn) - Autosplenectomy --> infxn w/ encapsulated organisms - salmonella osteomyelitis - vaso-occlusive crises - renal papillary necrosis - splenic sequestration crisis |
| tx for SCA? | hydroxyurea (inc HbF), BM txp |
| what causes target cells? | RBC dehydration (SCA, HbC dz, asplenia, liver dz, thalassemias) |
| what causes autosplenectomy in SCA? | chronic erythrostasis leads to splenic infarction, fibrosis and shrinkage |
| what is the genetic difference in the alpha and beta chains for HbA? | α-globins are encoded by a pair of genes on chromosome 16 whereas β-globins are encoded by a single gene on chromosome 11 |
| cause of anemia prevalent in Mediterranean populations | β thalassemia |
| most common genetic cause of β+ thalassemia | promoter region mutations |
| most common genetic cause of β0 thalassemia | chain terminator mutations |
| genotype of thalassemia major? | β0/β0 (HbA absent), β+/β+ or β0/β+ (HbA reduced) |
| genotype of thalassemia minor? | heterozygous carriers of one β+ or β0 allele |
| how does α-thalassemia manifest in newborns? | excess unpaired γ-globin (from HbF) clump together forming Hb-Barts leading to hydrops fetalis (fatal) |
| how does α-thalassemia manifest in older children and adults? | excess unpaired β-globin (from HbA) forms HbH tetramers --> HbH disease (tissue hypoxia and moderately severe anemia) |
| in what population is HbH disease common? | Asians |
| genotype of silent carrier of α-thalassemia? | -/α α/α |
| genotype of α-thalassemia trait? | -/- α/α (Asian), -/α -/α (African) |
| genotype of HbH disease? | -/- -/α |
| genotype of hydrops fetalis? | -/- -/- (no α alleles) |
| pathogenesis of paroxysmal nocturnal hemoglobinuria? | acquired mutations in phosphatidylinositol glycan complementation group A gene (PIGA - makes surface proteins that inhibit complement-mediated lysis) --> complement lysis of RBCs, PLTs, WBCs |
| why is PNH more active at night? | low resp --> mild acidosis --> increase activity of complement |
| abnml lab finding in PNH? | hemosiderinuria |
| difference between direct and indirect Coombs test? | Direct: anti-Ig Ab added to pt's RBCs clumps if serum has anti-RBC surface Ig Indirect: normal RBCs added to pt's serum, clump if serum has anti-RBC surface Ig |
| anemia characterized by IgG-mediated membrane damage of RBCs; esp assoc'd with α-methyldopa, and large IV doses of penicillins and cephalosporins | warm agglutinin autoimmune hemolytic anemia |
| anemia associated with IgM-mediated hemolysis after infxn by Mycoplasma pneumoniae, EBV, CMV, influenza, HIV | cold agglutinin autoimmune hemolytic anemia |
| causes of microangiopathic hemolytic anemia? | prosthetic valves or AS; DIC, TTP-HUS; SLE malignant HTN |
| schistocytes, burr cells, helmet cells and triangle cells on PBS indicate what class of anemias? | microangiopathic hemolytic anemia |
| causes of microcytic, hypochromic anemia? | iron def; thalassemias; lead poisoning; sideroblastic anemia |
| anisopoikilocytosis, low retic, large, hyper-segmented neutrophils. Dx? | megaloblastic anemia |
| pathogenesis of pernicious anemia? | autoimmune gastritis --> loss of parietal cells --> dec IF --> dec abs of B12 --> folate trapped in intermediate form --> dec DNA synthesis |
| why are both B12 and folate essential for DNA synthesis? | B12 takes Me from N-methylFH4 and turns homocysteine into methionine and frees folate to convert dUMP to dTMP --> DNA |
| causes of B12 deficiency? | malnutrition (alcoholics); malabsorption (Crohns); pernicious anemia;Diphyllobothrium latum infxn |
| causes of neuro sxs of B12 def? | B12 used to convert methylmalonyl CoA to succinyl CoA; deficiency --> methylmalonate and propionate buildup --> incorporation of abnml fatty acids into neuronal lipids |
| findings in B12 def? | -inc homocysteine -inc methymalonic acid -hypersegmented neut -glossitis |
| causes of folate def? | - malnutrition (alcoholics) - malabsorption- impaired metabolism (methotrexate, TMP) - inc requirement (preg, hemolytic anemia) |
| difference in lab findings of B12 and folate def? | B12 = inc Hcy and methylmalonate Folate = inc Hcy but normal methylmalonate |
| what drugs interfere with the absorption of folate? | phenytoin and oral contraceptives |
| what drugs interfere with the metabolism of folate? | folic acid antagonists (methotrexate, TMP) |
| what stain detects hemosiderin deposits? | Prussian blue stain |
| function of hepcidin? | inhibits iron transfer from enterocyte to plasma; suppresses iron release from macrophages |
| MCC of iron deficiency in developed countries? | GI blood loss |
| what causes koilonychia, alopecia, atrophy of tongue and gastric mucosa, pica, and intestinal malabsorption? | severe, chronic iron deficiency |
| Plummer-Vinson syndrome? | esophageal webs, microcytic hypochromic anemia, and atrophic glossitis |
| iron deficiency anemia: serum iron? TIBC? Ferritin? % sat? | iron LOW TIBC HIGH Ferritin LOW % sat VERY LOW |
| ACD: serum iron? TIBC? Ferritin? % sat? | iron LOW TIBC LOW Frtn HIGH % sat NORMAL |
| Hemochromatosis: serum iron? TIBC? Ferritin? % sat? | iron HIGH TIBC LOW Frtn HIGH %sat VERY HIGH |
| Pregnancy/OCP use: serum iron? TIBC? Ferritin? % sat? | iron NORMAL TIBC HIGH Frtn NORMAL %sat LOW |
| causes of ACD? | - chronic microbial infxn (osteomyelitis, bact endocarditis, lung abscess) - chronic immune disorders (RA, regional enteritis) - Neoplasms (lung and breast carcinoma, Hodgkin lymphoma) |
| pathogenesis of ACD? | inflammatory mediators (IL-6) stimulate inc hepatic production of hepcidin which causes macrophage sequestration of iron; No retics d/t low EPO levels |
| MCC of aplastic anemia? | exposure to chemicals and drugs (cancer chemo, benzene, chloramphenicol, gold salts) |
| Fanconi anemia? | autosomal recessive, defects in multiprotein complex required for DNA repair lead to aplastic anemia |
Created by:
csheck
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