week 5: morphology and Hbopathies Flashcards
• What are Heinz bodies?
o Formed by damage to hemoglobin through oxidative stress leading to irreversible hemichrome oxidation and precipitation.
o Purple-blue inclusions visible only after supravital stain
o Seen in: Alpha thalassemia, Congenital hemolytic anemia, G6PD deficiency
• What is basophilic stippling?
o Indicates toxic injury to the bone marrow. May also appear with severe anemia, such as megaloblastic anemia
o Variable size of granules distributed throughout cell
o Seen with Lead poisoning, Myelofibrosis
• What is the fate of heme after hemolysis?
o Excess Hb dimers in blood= hemoglobinemia
o Excess dimers in kidney -> hemoglobinuria
o Hb complex turned to bilirubin in M0 or liver -> biliary system
• What is Erythrocyte Sedimentation rate (ESR)?
o Rate at which RBCs settle in an hour
o Commonly performed, simple and inexpensive lab test to assess overall inflammation.
o Used to track the progress of a disease or to monitor treatment. “sickness index”
o Not used diagnostically
o Results directly correlate with the amount of fibrinogen in anticoagulated blood.
• What causes the ESR to increase?
o The normal negative cell surface charge of RBCs, “zeta potential”, makes RBCs repel each other
o Inflammatory proteins (acute phase reactants), mainly fibrinogen, neutralize the normal zeta
o RBCs no longer repel, but stack on each other= Rouleaux formation
o Larger mass of cell settles faster
• What is ESR used for?
o Follow the course of a disease – in general, as the disease worsens the ESR increases and as the disease resolves the ESR decreases
o Can be used to monitor therapy – especially for inflammatory autoimmune diseases
• What are the limitations to ESR?
o Nonspecific, nonsensitive
o May NOT be elevated in active disease
o Many factors can alter the test results
• What factors can interfere with ESR?
o Low results if test not set up within 3 hours of sample collection
o Pregnancy (2nd & 3rd tri) may elevate
o Menstruation may elevate
o Sedimentation tube must be vertical
o Some anemia’s falsely increase – correction nomograms are available
o Polycythemia & sickle cell disease decreases
o Protein-producing malignancies falsely increase value
o Any bubble in column invalidates the test
• What are some dzs that can increase ESR?
o Chronic renal failure
o Malignant diseases
o Bacterial infections
o Inflammatory diseases / Autoimmune Disease
o Necrotic diseases, MI
o Diseases assoc. with increased plasma proteins
o Assists in the diagnosis for: polymyalgia rheumatica and temporal arteritis (may be > 100 mm/hr)
• What szs can falsely decrease the ESR?
o Sickle cell disease – cells severely distorted & cannot form rouleaux
o Hereditary spherocytosis – cells are too spherical, do not stack in rouleaux
o Hypofibrinogenemia – decreased protein inhibits aggregation & settling of RBCs
o Polycythemia vera – increased RBC counts inhibit settling due to simple concentration interference
• What is the structure of hemoglobin?
o 4 polypeptides (globins), 2 alpha, 2 beta
o Each globin has a heme (porphyrin (red pigement) with Fe=metallo-porphyrin), which has O2 attracting properties
o Oxy-Hb or deoxyHb
• What are the normal variants of Hb?
o Hb A: 97% of total cells Hb; 2a and 2B
o HbA2: <3%; 2a and 2d
o HbF: 1%; 2a and 2g; predominant during fetal development; 50-80% at birth, 8% at 6 months
• What are hemoglobinopathies?
o Inherited defects in globin structure mostly involving a single amino acid substitution
o family of genetic disorders caused by:
o 1- Production of a structurally abnormal hemoglobin molecule (Qualitative hemoglobinopathies)
o Or: 2- Synthesis of insufficient quantities of normal hemoglobin (Quantitative hemoglobinopathies)
o Or: 3- both (rare).
• What is Thalassemia?
o A genetic blood disorder where the body makes reduced amounts of globin chains.
o 2 main types: affects either alpha or beta chains (ie Alpha Thalassemia)
o In major or minor forms: major=homozygous, minor=heterozygous
• What is beta thalassemia major?
o Children (cooley’s anemia): anemia in first year, facial bone deformities, fatigue, jaundice, growth failure, SOB
o HbA1 5-20%, HbA2 2-3%, HbF 65-100%
o Poikylocytic cells: elliptocytes, schistocytes, target cells, tear drop, spherocytes, hypochromic
• What is thalassemia minor?
o Beta thalassemia minor is most common form (one beta chain is affected)
o Results in mild microcytic hypochromic anemia otherwise no clinical symptoms
• What are the abnormal, clinically significant Hb variations?
o Hb S: Predominant in people with sickle cell disease. Disease exists on beta chain.
o Hb C: Disease is relatively benign with mild hemolytic anemia and splenomegaly
o Hb E: Mild hemolytic anemia and splenomegaly. Extremely common in SE Asia
o Hb Constant Spring: Alpha chain is abnormally long resulting in a thalassemic phenotype.
o Hb H: Composed of 4 beta chains. Happens in extreme limitation of alpha chains.
o Hb Barts: No alpha chains are produced. Most individuals die in utero
• How can you see sickle cell Hb on electrophoresis?
o HbA (normal) is more negatively charged than HbS, so moves farther o Val in sickle cell is neutral, but Glu is normal is negative
• Why is beta thalassemia clinically more severe?
o A chains dissociate into monomers more readily than B chins, so B chains form hemichromes at a faster rate
• What is sickle cell anemia? Hb? Incidence? Signs?
o Genetic trait causing hemoglobin irregularities
o Glutamic acid is substituted for valine; Allowing the polymerization of sickle hemoglobin when deoxygenated
o S 80-100%; A1 0%; A2 2-3%; F 2%
o Incidence is 6 months of age; Anemia is moderate to severe with slight jaundice; Significant number of patients die before age 40
o Sickle crisis may produce small infarcts in various organs, abdominal & bone pain most common
• What is the difference between normal and sickle red cells?
o Normal: disc-shaped, deformable, life span 120 day
o Sickle: sickle-shaped, rigid, lives 20 days or less
• What is the significance of hemolysis and vaso-occlusion in sickle cell anemia?
o Hemolysis: red cell destruction causes anemia, varying degrees between pts; bone marrow dramatically increases production of RBCs, but can’t keep up with destruction
o Vaso-occlusion: sickle cells block small vessels, can produce tissue hypoxia; result is pain or damage to organs
• What is sickle cell trait?
o Heterozugous, SA
o Hb distribution: S 20-40%; A1 60-80%; A2 2-3%; F2%
o Incidence is about 8% of African Americans
o No anemia or clinical evidence of disease
o May develop splenic infarcts under hypoxic conditions
o Some persons develop hematuria
• What is Hemoglobin C disease?
o Autosomal recessive disorder
o Similar to Hb S but glutamic acid to lysine substitution
o Considered a benign hemoglobinopathy
o Causes mild hemolytic anemia
o Unstable hemoglobin precipitates in RBCs and forms crystals
o Spleen removes defective RBCs from circulation
o Decreases the risk of malaria
• Hb distribution in HbC dz? Incidence? Sxs?
o C 90-100%; A1 0%; A2 2-3%; F 2%
o Incidence is about 3% of African Americans from northern Africa
o Mild to moderate reduction in RBC lifespan
o Abdominal & bone pain occur, less severe than sickle disease
o Large number of target cells on blood smear (30-90%)
• What is the malaria hypothesis?
o Malaria is found in areas where there are high carrier rates of hemoglobinopathies
o Being a carrier protects you from Malaria so you have an evolutionary “advantage” over a non-carrier—Don’t know why
o Hb S – reduces oxygen tension in cells retarding growth of the parasite
o A thalassemia – confers susceptibility to a milder form of malaria; once contracted, the patient has immunity to the more severe form and increased survival
o B-thalassemia - ???; possibly a role in decreasing cell adhesions in the deadly cerebral form of malaria
• How is heme synthesized?
o 85% of total heme synthesis occurs in red blood cells (RBC); Ceases when RBC’s mature
o Heme stimulates protein synthesis in reticulocytes
o The liver is the main non-RBC source of heme synthesis; used mainly for the synthesis of the cytochrome P450 class of enzymes that are involved in detoxification
o 2 succinyl CoA + glycine –(ALA synthase in mito IMS)-> –(porphobilinogen synthase in outer membrane)->cytosol->uroporphyrinogen III -> coporphyrinogen III ->IMS->protoporphyrinogen IX –(ferrochelatase)->heme
• What are porphyrias?
o A group of disorders caused by deficiencies of enzymes of the heme biosynthetic pathway.
o Two cardinal symptoms in patients with porphyria are photosensitivity and neurologic disturbances
o Acute: Affect the nervous system. Ssx come on quickly and last a short time. Sx: abdominal pain, vomiting, constipation, diarrhea. Sometimes seizures, anxiety and hallucinations can occur; may be life threatening.
o Cutaneous: affect the skin. Once exposed to sun, skin becomes fragile and blistered, leading to infection, changes in skin pigmentation and hirsutism
• How are porphyrias defined by where the damaging compounds originate?
o Erythropoietic (bone marrow): Low number of RBCs , enlargement of the spleen
o Hepatic (liver): Abnormal liver function, increased risk of developing liver cancer
o Mixed: Both hepatic and erythropoitic
o Acquired: No genetic component, drug induced or due to lead poisoning
• What is an example of an acquired porphyria?
o Lead poisoning: Pb inhibits bone marrow delta-aminolevulinic acid dehydratase (ALAD), a key enzyme in heme synthesis.
o Then the highly reactive oxyradical Delta-aminolevulinic acid (ALA) heme precursor accumulates, and is reported to cause liver cancer.
o Basophilic stippling in RBC’s
• What lab testing is done for porphyrias?
o from blood, random or 24 hour urine, and/or a stool sample
o If acute or neurologic porphyria is suspected, a sample should be taken during an acute attack.
o Testing measures porphorins and their toxic precursors that have built up in tissue and fluids.
o Specialty labs may also measure for involved enzymes or genetic testing
• What labs would you do for different porphyria sxs?
o Acute neuroviscerial: urine PBG and ALA; if increased, further test to find which P
o Sun-induced: erythrocyte protoporphyrin conc; increased is EPP
o Skin lesions: plasma or urine porphyrin profile; increased, further differentiate
• What is the relationship between Hb, HCT, and RBC indices?
o All are interrelated RBC parameters
o In general, decreases in RBC leads to decreases in Hemoglobin & Hematocrit
o The relationship between these 3 parameters allows calculation of the RBC indices
• How is Hb measured?
o Most common method used to measure total hemoglobin content is spectrophotometric analysis. Based on the premise that substances absorb light energy at different wavelengths.
o Spectrophotometry: RBCs lysed, release Hb; blue/green wavelengths shone through; light not absorbed is analyzed (Beer’s law) to determine Hb content
• What are normal Hb levels? Interfering factors?
o Males: 14.0-17.4 g/dL
o Females: 12.0-16.0 g/dL
o Children: 11.0-16.0 g/dl
o Very high WBC counts; Severe lipidemia; RBC abnormalities; Increased turbidity; Increased bilirubin
• What can cause decreased Hb levels?
o Decreased RBCs: bone marrow defects, renal disease, cell destruction, blood loss
o Hemoglobinopathies
o Lead poisoning
o Iron deficiency
o Increased blood volume: Pregnancy, over-hydration
What can cause increased Hb levels?
o Increased RBCs: Polycythemia vera; renal tumors o COPD o Pulmonary fibrosis o Heart disease o Decreased blood volume: Dehydration
What is hypochromasia?
o Variation in Hb content
o Increase in RBCs central pallor, which occupies more than the normal third of cell diameter
o Found in: Fe deficiency, thalassemia
• What is hematocrit? How is it measured?
o Volume of RBCs, as a % of volume of whole blood
o Indirect measure of RBC number and volume, since it is directly affected by both
o Approx. 3x Hb value when RBCs are normal
o Old: centrifuge capillary tube, =”packed cell volume”, %
o New: computers based on RBC count and size; HCT=RBCxMCV / 10
• What are normal HCT values?
o Males: 42-52%
o Females: 36-46%
o Pregnant female: >33%
o Elderly: may be slightly decreased
• What can cause increased HCT values?
o Erythrocytosis o Congenital heart disease o Polycythemia vera (PCV) o Severe dehydration o Severe COPD
• What can cause decreased HCT values?
o Anemia; Hemoglobinopathies; Cirrhosis; Hemolytic anemia; Hemorrhage; Nutrient deficiencies; Bone marrow failure; Prosthetic valves; Renal disease; Normal Pg: 2nd trim; Rheumatoid/collagen vascular diseases; Blood cancers and malignancies
• What are some interfering factors with HCT?
o 1. RBC size has influence: larger RBCs associated with higher Hct because larger cells take up greater percentage of total volume
o 2. Extremely high WBC counts falsely decrease
o 3. Over and under hydration
o 4. Pregnancy decreases due to hemodilution in 2nd trim.
o 5. High altitudes increase due to hypoxia
o 6. Post-hemorrhage values not reliable for several hours
o 7. Drugs may decrease – chloramphenicol, penicillin
• What are RBC indices?
o describe the size and Hb content of RBCs.
o The relationships between HCT, Hb level, and the RBC are converted to RBC indices through mathematical formulas.
o used to help in the differential diagnosis of anemia.
o worked out and first applied to the classification of anemia’s by Maxwell Wintrobe in 1934
• what is mean corpuscular volume?
o Average volume of RBCs; Reported as fL, femtoliters.
o Derived from the RBC histogram by multiplying the # of RBCs by the size of the RBCs and multiplied by a calibration constant, or the mean of the red blood cell distribution histogram= MCV.
o Normal: 82-97 fL
o decreased MCV = microcytic RBCs (100 fL)
o Most useful of the indices: anemia is micro, macro, or normocytic based on MCV
• What is an RBC histogram?
o Represents relationship b/w RBC size and number
o If macrocytes are present, the peak will skew to right (left if microcytic)
• What factors can interfere with MCV calculation?
o Anything that affects RBC counts or RDW:
o Very high WBC count
o High concentration of very large platelets
o Agglutinated RBCs
o RBC fragments that fall below the 36 fL threshold
• What is mean corpuscular hemoglobin?
o The average weight of Hgb in a RBC, reported in pg, picograms. A calculated value.
o Normal range: 26-34 pg of Hgb/RBC.
o MCH = Hbx10 / #RBCs in millions
o decreased MCH: small RBCs contain less Hgb
o Increased MCH: large RBCs contain more Hgb
• What are interfering factors with MCH?
o Anything that interferes with hemoglobin readings
o Anything that interferes with RBC counts
What is the mean corpuscular hemoglobin concentration?
o A “weight to volume” ratio of the average concentration of Hgb in a given volume of RBCs. A Calculated value. Reported as g/dL.
o Normal MCHC = 32-36 g/dL
o MCHC= Hbx100 / HCT
o Used to classify anemia type; normal MCHC=normochromic anemia; <30 = hypochromic; hyperchromic doesn’t exits
• Why can’t RBCs be considered hyperchromic?
o MCHC values have a theoretical limit of 37; only 37 g/dl of hemoglobin can fit into an RBC!
o Machines calc HCT based on MCV and #RBC -> as #RBCs decrease, MCHC increases
o machines may indicate MCHC >37 in those with spherocytosis, hyperlipidemia, cold agglutinins, & rouleaux formation (some RBC problem that falsely lowers the machine’s RBC count)
what are some normocytic, normochromic anemias?
o Chronic illness – the “anemia of chronic disease” (early stages)
o Renal disease- EPO
o Acute blood loss
o Aplastic anemia
o Acquired hemolytic anemia
o Early Fe def: make less RBC b/c less Fe, but cells still have adequate Hb just fewer cells
• What are some microcytic, hypochromic anemias?
o Iron deficiency due to: Malabsorption, Malnutrition, Loss of blood (non-acute)
o Sideroblastic
o Lead poisoning
o Anemia of chronic disease (later stages)
o Thalassemia
• What are some macrocytic, normochromic anemias?
o Vitamin B12 or folic acid deficiency
o Pernicious anemia
o Side effects of chemotherapy
o Myelodysplastic syndrome: BM abnormalities that results in decreased production of RBCs & WBCs often a precursor to development of Acute Myelogenous Leukemia (AML)
• Pattern 1:
o RBC elevated o HB elevated o HCT elevated o MCV normal o MCH normal o MCHC normal o RDW normal o EPO decreased
• Pattern 2:
o RBC decreased o Hb decreased o HCT decreased o MCV elevated o MCH elevated o MCHC normal o RDW elevated
• Pattern 3:
o RBC decreased o Hb decreased o HCT decreased o MCV decreased o MCH decreased o MCHC decreased o RDW elevated/normal
• Pattern 4:
o RBC decreased o Hb decreased o HCT decreased o MCV normal o MCH normal o MCHC normal o RDW normal o BUN increased o Creatinine increased o Urinalysis +1 protein o EPO decreased
