Hematology & Oncology Flashcards
Microcytic Anemia
MCV division that occurs to maintain [Hgb]
Include: Iron deficiency anemia, anemia of chronic disease, sideroblastic anemia, & thalassemia
Iron Deficiency Anemia
Microcytic Anemia due to decreased Iron levels
Most common type of anemia; lack of iron is most common nutritional deficiency in the world
=Microcytic, hypochromic RBCs w/ ↑ RDW, ↑ TIBC, & ↑ FEP (free erythrocyte protoporphyrin), ↓ ferritin, ↓ serum iron, & ↓ % saturation (normal is 33%)
Tx - supplemental iron (ferrous sulfate) + treat underlying cause
Stages of Iron Deficiency
1 - Storage iron is depleted = ↓ ferritin; ↑ TIBC
2 - Serum iron is depleted = ↓ serum iron; ↓ % sat
3 - Normocytic anemia - BM makes fewer, but normal-sized, RBCs
4 - Microcytic, hypochromic anemia - BM makes smaller & fewer RBCs
Anemia of Chronic Disease
Microcytic Anemia associated w/ chronic inflammation (most common type of anemia in hospitalized patients),
Chronic disease results in acute phase reactants from the liver including Hepcidin
Hepcidin sequesters iron by limiting iron transfer from macrophages to erythroid precursors & suppressing EPO production (aiming to prevent bacteria from accessing iron)
= ↑ ferritin & FEP; ↓ TIBC, serum iron & % saturation
Tx - address underlying cause; Exogenous EPO useful in some Pt (esp. those w/ cancer)
Sideroblastic Anemia
Microcytic Anemia due to defective protoporphyrin synthesis
Conversion of succinyl CoA to ALA by ALAS (aminolevulinic acid synthetase w/ B6 cofactor) is rate limiting step; ALAD and ferrochelatse - inhibited by Lead
Can be Congenital (ALAS defect most common) or Acquired - Alcohol (mitochondrial poison), Lead poisoning, B6 deficiency (commonly from AE of isoniazid Tx for TB)
= ↑ ferritin, serum iron and % sat; ↓ TIBC = iron overloaded state
Iron enters mitochondria & remains trapped there (as there is not protoporphyrin for it to be attache to) and Iron-laden mitochondria for a ring around the nucleus of erythroid precursors = ringed-sideroblasts
Thalassemia
Microcytic Anemia due to decreased synthesis of globin chains of Hgb
Inherited mutation (carriers are protected from P. falciparum)
α-thalassemia
usually due to gene deletion (normally 4 α genes present on chromosome 16)
1 gene deleted = asymptomatic
2 genes deleted = mild anemia w/ ↑ RBC count
Cis - (same chromosome) seen in asians, worse cuz ↑
risk of severe thalassemia in offspring
Trans - seen in Africans (including African Americans)
3 genes deleted = Severe anemia, HBH (β chain tetramers) damage RBCs
4 genes deleted = lethal in utero (hydrops fetalis), HB Barts (gamma chain tetramers) damage RBCs
β-thalassemia
usually due to gene mutation (normally 2 β genes present on chromosome 11) - ween in indeviduals of African & Mediterranean descent
β-Thal minor (β/β+) - usually asymptomatic w/ ↑ RBC count; microcytic, hypochromic RBCs & target cells on blood smear; ↓ HbA w/ ↑ HbA2 & HbF
β-Thal major (β°/β°) - presents w/ severe anemia a few months after birth (high HbF temporarily protective)
=unpaired α chains precipitate & damage RBC membrane
Extramedullary hematopoiesis = hepatosplenomegaly + crewcut skull & chipmunk facies (due to hematopoiesis in skull and facial bones)
Smear show microcytic, hypochromic RBCs w/ target cells & nucleated RBCs; HbA2 & HbF w/ little or no HbA
Tx - chronic transfusions often necessary (leads to risk or secondary hemochromatosis)
Macrocytic Anemia
MCV > 100 µm3
Most commonly due to folate or Vit B12 deficiency (necessary for synthesis of DNA precursors)
=impaired division & enlargement of RBC precursors leads to megaloblastic anemia
=impaired division of granulocytic precursors leads to hypersegmented neutrophils (>5 lobes)
=Megaloblastic change also seen in rapidly-dividing epithelial cells
Other causes of macrocytic anemia (w/out megaloblastic change) = alcoholism, liver disease & drugs (ex 5-FU)
Folate Deficiency
Dietary folate is obtained from green vegetables & some fruits; absorbed in the jejunum
Causes = poor diet, increased demand (pregnancy, cancer, hemolytic anemia), & folate antagonists (ex methotrexate)
= Macrocytic RBCs & hypersegmented neutrophils
Glossitis (inflammation of tongue epithelium)
↑ serum homocysteine (↑ risk of thrombosis)
↓ serum folate
normal methylmalonic acid
Vitamin B12 Deficiency
Complexed to animal-derived proteins (get from meat)
-salivary gland liberates, then binds R-binder; pancreatic proteases in duodenum detach B12 from R-binder; IF binds B12 in small bowel, & IF-B12 absorbed in ileum
Less common than folate deficiency due to large hepatic stores (takes years to develop)
Pernicious anemia most common cause (autoimmune destruction of parietal cells = IF deficiency); pancreatic insufficiency & damage to terminal ileum = other causes
= Macrocytic RBCs w/ hypersegmented neutrophils
Glossitis
↑ Serum homocysteine (↑ risk of thrombosis)
↓ serum Vitamin B12
↑ methylmalonic acid = Subacute combined
degeneration of spinal cord
(B 12 is a cofactor for the conversion of methylmalonic acid to succinyl CoA)
Normocytic Anemia
Anemia w/ normal sized RBC (MCV = 80-100)
Due to ↑ peripheral destruction or underproduction
Reticulocytes (young RBCs = large cells w/ bluish cytoplasm due to residual RNA) help distinguish etiology
- Normal Retic count is 1-2%
- proper functioning BM respond to anemia by ↑ RC - >3%
- corrected RC = RC * Hct/45
>3% = good response & suggests peripheral destruction
<3% = poor BM response & suggests underproduction
Extravascular Hemolysis
involves RBC destruction by the reticuloendothelial system (macrophages of the spleen, liver & lymph nodes)
= Macrophages consume RBCs and break down Hgb
Pw/ Anemia w/ splenomegaly, jaundice due to unconjugated bilirubin, ↑ risk of bili gallstones, & bone marrow hyperplasia
Labs - ↑ unconjugated bili
- Corrected RC >3%
Intravascualr hemolysis
Involves destruction of RBCs w/in the blood vessels
= ↓ haptoglobin (binds Hgb in blood and takes it to spleen to be salvaged)
=hemoglobinemia -> hemoglobinuria -> hemosiderinuria (renal tubule cells pick up some of the hemoglobin that is filtered in the urine & break it down into iron, which accumulates as hemosiderin, which then ends up in the urine when the tubular cells are shed)
Hereditary Sperocytosis
Normo- anemia w/ predominant extravascular hemolysis
Inherited defect of RBC cytoskeleton-membrane tethering proteins (ankyrin, spectrin, or band 3.1)
= membrane blebs for & are lost over time, as membrane is lost RBCs for spherocytes which are less able to maneuver the splenic sinusoids & are consumed by splenic macrophages => anemia
Labs - Spherocytes w/ loss of central pallor; ↑ RDW, ↑ MCHC, ↑ unconjugated bili
- splenomegaly & ↑ risk of bili gallstones
Dx- osmotic fragility test (↑ fragility in hypotonic solution)
Tx - splenectomy = anemia resolves, but spherocytes persist & Howell-Jolly bodies emerge on blood smear
Howell - Jolly bodies = fragments of nuclear material
↑ risk for aplastic crisis w/ parvovirus B19 infection
Sickle Cell Anemia
Normo- anemia w/ predominant extravascular hemolysis
AR mutation of β chain (glutamic acid -> valine)
(trait = 1 mutation, disease present w/ 2 β chain mutations) (β mutation has protective role against falciparum malaria)
=HbS polymerizes when deoxygenated & polymers aggregate into needle-like structures = sickle cells
↑ risk or sickling w/ hypxemia, dehydration, & acidosis
Labs - Sickle cells & target cells on blood smear (in SCD)
- Metabisulfite screen causes cellw w/ any amount of HbS to sickle (= + in both SCT & SCD)
-HbS presence confirmed w/ electrophoresis
-Howell-Jolly bodies on blood smear
SCD = 90% HbS, 8% HbF, 2% HbA2
SCT = 55% HbA, 43% HbS, 2% HbA2
Note - from expansion of hematopoiesis & hepatomegaly from extramedullary hematopoiesis
Dactylitis = swollen hands & feet due to vaso-occlusive infarcts in bones = common presenting sign in infants (around 6 months, as [HbF] decreases)
Autosplenectomy common = ↑ risk of infection w/ encapsulated organisms (S. pneumonia, H. flu…)
↑ risk of Salmonella paratyphi osteomyelitis
Encapsulated organism infection = most common cause of death in SC children
Acute chest syndrome (from vaso-occlusion in pulmonary microcirculation) = most common cause of death in adult patients (often precipitated by pneumonia)
Hemoglobin C
Normo- anemia w/ predominant Extravascular hemolysis
AR mutation in β chain of Hgb (glutamic acid -> lysine)
Pw/ mild anemia due to extravascular hemolysis
Characteristic HbC crystals in RBCs on blood smear
HbC, lyCine, Crystals
Paroxysmal Nocturnal Hemoglobinuria (PNH)
Normo- anemia w/ predominant intravascular hemolysis
Acquired defect in myeloid stem cells (= absent GPI); renders cells susceptible to destruction by complement
(normally - GPI secures DAF to RBC membrane; DAF inhibits C3 convertase = protects against complement)
= intravascular hemolysis occurs episodically, often at night (when mild respiratory acidosis develops) = hemoglobinemia & hemoglobinuria (esp in morning)
- compliment lysis RBCs, WBCs & platelets
Sucrose test used to screen; acidified serum test or flow cytometry are confirmatory tests
Main cause or death = Thrombosis of hepati, portal, or cerebral veins (destroyed platelets release cytoplasmic contents into circulation, inducing thrombosis)
Complications = iron deficiency anemia (due to chronic loss of Hgb) & AML (develops in 10%)
G6PD (Glucose-6-phosphate dehydrogenase) Deficiency
Normo- anemia w/ predominant intravascular hemolysis
XR disorder = ↓ half-life of G6PD = renders cells susceptible to oxidative stress
↓ G6PD -> ↓ NADPH -> ↓ glutathione (an antioxidant) = oxidative injury by H2O2 -> intravascular hemolysis
African variant = mildly ↓ G6PD T1/2 = mild intravascular hemolysis w/ oxidative stress
Mediterranean variant = markedly ↓ G6PD T1/2 = marked intravascular hemolysis w/ oxidative stress
(high carrier frequency in both populations is likely due to protective role against falciparum malaria)
Oxidative stress precipitates Hb as Heinz bodies (can only be seen w/ a special stain - Heinz preparation), which are removed from RBCs by splenic macrophages = bite cells
Pw/ hemoglobinuria & back pain hours after exposure to oxidative stress
Oxidative stresses include infections, drugs (primaquine, sulfas & dapsone…) & fava beans
Immune Hemolytic Anemia (IHA)
Normo- anemias w/ predominant Intravascular hemolysis
Ab-mediated (IgG or IgM) destruction of RBCs
IgG mediated usually involves extravascular hemolysis (binds in warm areas of body = centrally) - Ab coated RBCs consumed by splenic macrophages = spherocytes
- Associated w/ SLE, CLL, drugs (penicillin, cephalosporins, α-methyldopa)
- Tx = cessation of offending drug; steroids, IVIG, and splenectomy (if necessary)
IgM mediated usually involves intravascular hemolysis (bind RBCs & fix compliment in cold temp or extremities (cold agglutinin))
-Associated w/ Mycoplasma pneumoniae & infectious mononucleosis
Dx w/ Indirect or Direct Coombs test
Microangiopathic Hemolytic Anemia
Intravascular hemolysis that results from vascular pathology; RBCs are destroyed as they pass through circulation
Occurs w /microthrombi (TTP-HUS, DIC, HELLP), prosthetic heart valves, & aortic stenosis; when present, microthrombi produce schistocytes on blood smear
Normo- anemia w/ predominant intravascular hemolsysis
- Iron deficiency anemia can occur w/ chronic hemolysis
Malaria
Infection of RBCs & liver w/ Plasmodium spp. transmitted by female Anopheles mosquito
= RBCs rupture as a part of the Plasmodium life cycle, resulting in intravascular hemolysis and cyclical fever (daily w/ falciparum, every other day w/ vivax & ovale)
Spleen also consumes some infected RBCs = mild extravascular hemolysis w/ splenomegaly
= Normo- anemia w/ predominant intravascular hemolysis
Anemia due to Underproduction
↓ production of RBCs by bone marrow; characterized by low corrected reticulocyte count (<3%)
Etiologies include
1) causes of micro & macrocytic anemia
2) Renal failure (↓ EPO production by peritubular interstitial cells)
3) Damage to BM precursor cells (may result in anemia or pancytopenia)
Parvovirus B19
Infects progenitor RBCs & temporarily halts erytropoiesis; leads to significant anemia in the setting of preexisting marrow stress (e.x. sickle cell anemia)
Tx - supportive (infection is self-limited)
Aplastic Anemia
Damage to hematopoietic stem cells, resulting in pancytopenia w/ low retic count
Etiologies include drugs/chemicals, viral infections, & autoimmune damage
Biopsy reveals empty & fatty marrow
Tx - cessation of causative agents & supportive care w/ transfusions and marrow-stimulating factors (EPO, GM-CSF, G-CSF…)
- immunosuppression may be helpful (some cases due to abnormal T-cell activation w/ cytokine release)
- last resort = BM transplant
Myelophthisic process
pathologic process (e.g. metastatic cancer) that replaces bone marrow = hematopoiesis is impaired = pancytopenia
Disorders of Primary Hemostasis
Primary Hemostasis = Forming a platelet plug (through GPIb, GPIIb/IIIa, fibrinogen)
= usually due to abnormalities in platelets
Clinical features include mucosal & skin bleeding
- epistaxis (most common), hemoptysis, GI bleeds, hematuria & menorrhagia; intracranial bleeds if severs
- petechiae (1-2mm), purpura (>3mm), ecchymosis (>1cm)
Labs - Platelet count <50 K/uL (leads to symptoms)
↑ bleeding time
blood smear to asses #/size of platelets
BM biopsy to assess magakaryocytes
Immune Thrombocytopenic Purpura (ITP)
Quantitative platelet disorder due to autoimmune production of IgG against platelet antigen (e.x.GPIIb/IIIa - cross-links w/ fibrin)
-Auto-Ab produced by plasma cells in the spleen & Ab-bound platelets are consumed by splenic macrophages
Most common cause of thrombocytopenia in children & adults
-Divided into acute & chronic forms
Labs - ↓ platelets (often <50 K/ul),
- Normal PT/PTT
- ↑ megakaryocytes on BM biopsy
Tx - initial = corticosteroids (adults may show early response and then relapse)
- IVIG is used to raise the platelet count in symptomatic bleedint (but its effect is short lived)
- Splenectomy eliminates the primary source of Ab & the site of platelet destruction
Acute ITP
arises in children weeks after a viral infection or immunization
Self-limited, usually resolving w/in weeks of presentation
Chronic ITP
Arises in adults, usually women of child-bearing age.
May be primary or secondary (e.x. SLE)
IgG can cause the placenta = may cause short lived thrombocytopenia in offspring
Microangiopathic Hamolytic Anemia
Quantitative platelet disorder due to pathologic formation of platelet microthrombi in small vessels
- platelets are consumed in the formation of microthrombi = thrombocytopenia
- RBCs are sheared as they cross microthrombi = hemolytic anemia w/ schistocytes
Seen in TTP & HUS
Labs - Thrombocytopenia w/ ↑ bleeding time
- Normal PT/PTT
- Anemia w/ schistocytes
- ↑ megakaryocytes on BM biopsy
= Skin & mucosal bleeding; Fever, Renal insufficiency (more w/ HUS), CNS abnormalities (more w/ TTP)
Tx - involves plasmapheresis & corticosteroids (particularly in TTP)
Thrombotic Thrombocytpenic Purpura (TTP)
Quantitative platelet disorder due to ↓ ADAMTS13 - normally cleaves vWF multimers into smaller monomers for degradation
↓ ADAMTS13 is usually due to an acquired auto-Ab (most commonly seen in adult females)
= Large, uncleaved vWF multimers lead to abnormal platelet adhesion; resulting in microthrombi
tend to be associated more with CNS manifestations
Hemolytic Uremic Syndrome (HUS)
Quantitative platelet disorder due to endothelial damage by drugs or infection
Classically seen in children w/ E coli O157:H7 dysentery (from exposure to under-cooked beef)
= E coli verotoxin damages endothelial cells (& ADAMST13) resulting in platelet microthrombi
Causes damage particularly in the kidneys
Bernard-Soulier Syndrome
Qualitative platelet disorder due to a genetic GPIb deficiency = platelet adhesion is impaired
GPIb on platelets binds vWF
Blood smear shows mild thrombocytopenia w/ enlarged platelets
Glanzmann thrombasthnia
Qualitative platelet disorder due to a genetic GPIIb/IIIa deficiency = platelet aggregation is impaired
GPIIb/IIIa on platelets crosslinks w/ fibrin
Other Qualitative Platelet disorders
Aspirin - irreversibly inactivates COX = lack of TXA2 impairs platelet aggregation
-TXA2 released by platelets signals for aggregation
Uremia - disrupts platelet functions; both adhesion & aggregation are impaired
Uremia due to build up of nitrogenous waste products from poor kidney function
Disorders of Secondary Hemostasis
Secondary Hemostasis = Stabilizes the weak platelet plug via the coagulation cascade
Usually due to factor abnormalities
Labs - PT (measures extrinsic VII & common pathway)
- PTT (measures intrinsic XII, XI, IX, VIII & common)
= deep tissue bleeding into muscles & joints (hamarthrosis) & rebleeding after surgical procedures
Hemophilia A
Genetic VIII deficiency
XR but can be de novo
Pw/ deep tissue, joint & post-surgical bleeding
Labs = ↑ PTT (normal PT)
- ↓ FVIII
- normal platelet count & bleeding time
- PTT corrects in mixing study
Tx - recombinant FVIII