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Path 14 RBC

Path 14 RBC Bleeding Disorders

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