Chapter 22: Disorders of Red Blood Cells

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1

What is anemia?

A reduction in the oxygen-carrying capacity of the blood.

2

Anemia is not a disease but rather a symptom complex that may result from one of three underlying causes. What are they?

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  1. decreased production of RBCs
  2. blood loss
  3. increased destruction of RBCs
3

What is erythropoiesis?

The process of RBC production.

4

What is the primary stimulus for erythropoiesis?

oxygen demand (hypoxia)

5

What organ serves as the primary sensor or determining the level of oxygenation in the blood?

kidney

6

What hormone is released by the kidney in response to hypoxia, stimulating the bone marrow to release RBCs?

erythropoietin

7

What is the oxygen-carrying molecule of RBCs?

hemoglobin (Hb)

8

What is the basic structure of Hb?

It consists of two pairs of globin chains (i.e. α plus β, δ, or γ) around four oxygen-binding heme groups.

9

What percentage of RBC volume is composed of Hb?

33%

10

What are the seven main types of anemia?

  1. iron deficiency anemia
  2. folate deficiency anemia
  3. pernicious anemia
  4. sickle cell anemia
  5. thalassemia
  6. G6PD deficiency anemia
  7. aplastic anemia
11

What are the three main hemolytic anemias?

  1. sickle cell anemia
  2. thalassemia
  3. G6PD deficiency anemia
12

What is the most common type of anemia in the US?

iron deficiency anemia

13

What form of anemia is common in western Africa?

sickle cell anemia

14

What form of anemia is common in Asia?

aplastic anemia

15

What are the two main "microcytic" anemias?

  1. iron deficiency anemia
  2. thalassemia
16

What are the three main "normocytic" anemias?

  1. sickle cell anemia
  2. G6PD deficiency anemia
  3. aplastic anemia
17

What are the two main "macrocytic" anemias?

  1. pernicious anemia
  2. folate deficiency anemia
18

What are the three most common causes of iron deficiency anemia?

  1. menstruation
  2. pregnancy
  3. gastrointestinal bleeding
19

How can autoimmune diseases contribute to the development of iron deficiency anemia?

Diseases that cause chronic inflammation are associated with an increased demand for iron (anemia of chronic disease).

20
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What about this peripheral blood smear suggests a diagnosis of iron deficiency anemia?

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The blood smear shows microcytic red blood cells that have marked hypochromic central pallor.

21

What is the role of vitamin B12 (cobalamin) in the formation and growth of RBCs within bone marrow?

Vitamin B12 is a cofactor in methionine-associated enzymatic reactions required of protein synthesis.

22

What is the role of folate (folic acid) in the formation and growth of RBCs within bone marrow?

Folate is required for the synthesis of nucleotides, purines and pyrimidines of DNA and RNA.

23

What are the four main risk factors for folate deficiency?

  1. poor diet
  2. alcoholism
  3. malabsorption disorders
  4. pregnancy
24

Which type of anemia is caused by an inability to absorb vitamin B12 from the gastrointestinal tract?

pernicious anemia

25

What substance secreted by the gastric parietal cells is necessary for absorption of vitamin B12 and is deficient in pernicious anemia?

intrinsic factor

26

What specific genetic mutation is responsible for the sickle cell hemoglobin (HbS) of sickle cell anemia?

It results from substitution of valine for glutamic acid at the sixth residue of the β chain.

27

What is the difference between sickle cell "trait" and sickle cell "disease"?

Whereas sickle cell trait is the heterozygous state (i.e. HbAHbS), sickle cell anemia is the homozygous state (i.e. HbSHbS); more than 80% of the Hb is HbS.

28

Why is it called "sickle cell" anemia?

Because in the deoxygenated state (or at low pH), HbS polymerizes, distorting the RBC into a sickled shape.

29
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What about this peripheral blood smear suggests a diagnosis of sickle cell anemia?

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The blood smear shows characteristic abnormal sickle-shaped red blood cells.

30

What are the classic manifestations of sickle cell anemia in patients under 20 years of age? (5)

  1. painful events
  2. stroke
  3. acute chest syndrome
  4. acute anemia
  5. infection
31

What are the classic manifestations of sickle cell anemia in patients between 20 and 40 years of age? (5)

  1. osteonecrosis
  2. leg ulcers
  3. priapism
  4. liver disease
  5. gallstones
32

What are the classic manifestations of sickle cell anemia in patients over 40 years of age? (5)

  1. pulmonary hypertension
  2. nephropathy
  3. proliferative retinopathy
  4. cardiac enlargement
  5. arrhythmias
33
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What about this patient presentation suggests a diagnosis of sickle cell anemia?

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The leg ulcer, secondary to a vasoocclusive attack, and the deformed middle finger from dactylitis.

34

What is the cause of thalassemias?

Deletions or mutations of the α-globin or β-globin genes that result in defective globin synthesis.

35

What is the function of the enzyme glucose-6-phosphate dehydrogenase (G6PD) in RBCs?

It enables the RBC to convert carbohydrates into energy via the hexose monophosphate shunt pathway.

36

How does G6PD deficiency lead to anemia?

It results in production of methemoglobin, which causes RBC membrane alterations and hemolysis.

37

What are three signs and symptoms of anemia? (3)

  1. fatigue
  2. palpitations
  3. dyspnea
38

What are three signs and symptoms of iron deficiency anemia?

  1. impaired immunity
  2. diminished exercise tolerance
  3. decreased work performance
39

What are three signs and symptoms of G6PD deficiency anemia?

  1. acute intravascular hemolysis
  2. jaundice
  3. dyspnea
40

What are five signs and symptoms of sickle cell anemia?

  1. jaundice
  2. dactylitis
  3. leg ulcers
  4. organomegaly
  5. vasoocclusive crises
41

What are three signs and symptoms of aplastic anemia?

  1. weakness
  2. headaches
  3. bleeding (petechiae, ecchymoses, epistaxis)
42

What is a clinical sign specific to pernicious anemia?

premature graying of hair

43
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What about this patient presentation suggests a diagnosis of pernicious anemia?

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Three features more common in pernicious anemia;

  1. blue eyes
  2. vitiligo
  3. premature graying of the hair
44
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What about this patient presentation suggests a diagnosis of a nutritional deficiency anemia?

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Patients with nutritional deficiency anemia often have a red, smooth tongue and angular cheilitis.

45

What should be done if a dental patient presents with signs or symptoms suggestive of anemia?

They should be referred to a physician for evaluation.

46

What three tests are used to screen patients for anemia?

  1. Hb level
  2. hematocrit
  3. RBC indices
47

The RBC indices are used to screen patients for anemia. What are the four RBC indices?

  1. mean corpuscular volume (MCV)
  2. mean corpuscular hemoglobin (MCH)
  3. RBC distribution width (RDW)
  4. mean corpuscular hemoglobin concentration (MCHC)
48

How is anemia defined based on Hb level in the blood?

  1. less than 12 g/dL for women
  2. less than 13 g/dL for men
49

How are anemias classified based on MCV?

  1. MCV <80 fL is microcytic
  2. MCV of 80–100 fL is normocytic
  3. MCV >100 fL is macrocytic
50

How are anemias differentiated based on reticulocyte count as a percentage of RBCs?

  1. <0.5% indicates decreased RBC production (e.g. iron, B12, or folic deficiency)
  2. >1.5% indicates increased RBC production (e.g. hemolytic anemia or blood loss)
51

How are anemias differentiated based on the absolute reticulocyte count?

  1. <75,000/µL indicates hypoproliferative anemia (e.g. iron, B12, or folic deficiency)
  2. >100,000/µL indicates hyperproliferative anemia (e.g. hemolytic anemia or blood loss)
52

What tests are used to diagnose iron deficiency anemia? (5)

  1. CBC (microcytic anemia)
  2. serum iron (↓)
  3. serum ferritin (↓)
  4. total iron-binding capacity (↑)
  5. transferrin saturation (↓)
53

What tests are used to diagnose folate deficiency anemia? (2)

  1. CBC (macrocytic anemia)
  2. serum folate (↓)
54

What tests are used to diagnose pernicious anemia? (4)

  1. CBC (macrocytic anemia)
  2. serum vitamin B12 (↓)
  3. Schilling test
  4. serologic test
55

The Schilling test helps to establish the diagnosis of pernicious anemia. How is this test administered?

A fasting patient receives a small oral dose of radioactive vitamin B12, which is measured in the urine; normally, 7% is excreted in the first 24 hours, but in pernicious anemia less than 3% is excreted.

56

How does serologic testing help to establish a diagnosis of pernicious anemia?

It is used to detect autoantibodies against parietal cells and intrinsic factor, characteristic of pernicious anemia.

57
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What about this peripheral blood smear indicates a diagnosis of pernicious anemia?

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The smear shows macrocytic red blood cells with a hypersegmented polymorphonuclear leukocyte.

58

What tests are used to diagnose G6PD deficiency anemia? (6)

  1. CBC (normocytic anemia)
  2. reticulocyte count (↑)
  3. indirect bilirubin levels (↑)
  4. blood smear with methylene blue stain
  5. cyanide-ascorbate assay
  6. qualitative/quantitative test for G6PD
59
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What about this peripheral blood smear indicates a diagnosis of G6PD deficiency anemia?

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The methyl or crystal violet staining shows Heinz bodies (Hb precipitates) in red blood cells.

60

What tests are used to diagnose sickle cell anemia?

  1. CBC (normocytic anemia)
  2. reticulocyte count (↑)
  3. indirect bilirubin levels (↑)
  4. Sickledex (+)
  5. liquid chromatography showing HbS
  6. hemoglobin electrophoresis showing HbS
61

How does the Sickledex test help to establish a diagnosis of sickle cell anemia?

This test uses deoxygenating agents, which will cause RBCs to sickle in shape.

62

What tests are used to diagnose aplastic anemia? (5)

  1. CBC (normocytic anemia)
  2. reticulocyte count (↓)
  3. thrombocytopenia
  4. neutropenia
  5. bone marrow aspirate
63

What is the treatment for iron deficiency anemia?

iron supplements

64

What is the treatment for folate deficiency anemia?

folic acid supplements

65

What is the treatment for pernicious anemia?

cyanocobalamin injections

66

What are the treatments for sickle cell anemia? (3)

  1. prophylactic penicillin
  2. folic acid supplements
  3. hydroxyurea
67

Why are folic acid supplements given to patients with sickle cell anemia?

Due to increased erythropoiesis in sickle cell disease, patient may be at increased risk for folate deficiency, which may precipitate vasoocclusive crises.

68

Why is hydroxyurea given to patients with sickle cell anemia?

It induces production of HbF and thus prevents formation of HbS polymers.

69

What is the treatment for aplastic anemia for patients 50 years of age or younger?

stem cell transplantation

70

What test is required to prior to stem cell transplantation in patients with aplastic anemia?

Family human leukocyte antigen (HLA) to identify a histocompatible sibling.

71

What is the prognosis for HLA-matched related bone marrow transplantation in aplastic anemia?

It is curative for 80% to 90% of patients.

72

What is a common long-term complication of bone marrow transplantation in aplastic anemia?

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chronic graft-versus-host disease (GVHD)

73

Female dental patients should be queried regarding their menstrual cycle. Under what four conditions should the dentist recommend seeking medical evaluation?

  1. having regular periods but heavy flow
  2. noting changes in their menstrual flow
  3. stopping having periods prematurely
  4. bleeding between regular periods
74

Abonormal mensuration is a common cause of anemia in women. What is a common cause for anemia in men?

Anemia, particularly in men, may have a serious underlying disease such as peptic ulcer or carcinoma.

75
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What about this patient presentation suggests a diagnosis of anemia?

The patient's hand (left) shows obvious pallor compared to the physician's (right).

76

At what values for Hb, heart rate, and O2 saturation is the dental patient considered unstable, requiring routine treatment to be deferred until their health status improves?

  1. Hb less than 11 g/dL
  2. any abnormal heart rate
  3. oxygen saturation less than 91%
77

What three drugs are most commonly involved in drug sensitivity in patients with G6PD deficiency?

  1. sulfonamides (sulfamethoxazole)
  2. aspirin
  3. chloramphenicol
78

A G6PD deficient dental patient with severe periodontal disease begins experiencing febrile illness and elevated bilirubin. What does this indicate?

In patients with this type of anemia, dental infection may cause increased hemolysis.

79

What is the recommendation regarding the use of local anesthetic with epinephrine in patients with sickle cell anemia?

Some believe vasoconstrictors may cause vascular occlusion, but the benefits probably outweigh the risks.

80

What is the recommendation for general anesthesia in patients with sickle cell anemia?

If required, N2O-O2 should be used for short periods, with at least 50% O2 concentration provided.

81

Why must barbiturates and narcotics be avoided in patients with sickle cell anemia?

Suppression of the respiratory center by these drugs leads to hypoxia and acidosis, which may precipitate an acute crisis.

82

What two drugs can be used to achieve light sedation in patients with sickle cell anemia?

  1. midazolam
  2. nalbuphine
83

What is the recommendation for pain control in patients with sickle cell anemia?

Pain control may be attempted with use of acetaminophen and small doses of codeine.

84

Why must salicylates (e.g. aspirin) be avoided in patients with sickle cell anemia?

Because high doses of these drugs produce an “acid” effect that can precipitate an acute crisis.

85

Why are prophylactic antibiotics often recommended in sickle cell anemia when surgical procedures are performed?

In order to prevent wound infection or osteomyelitis (although there is no evidence supporting their use).

86

What three drugs can be used for antibiotic prophylaxis in patients with sickle cell anemia?

  1. penicillin
  2. amoxicillin
  3. clindamycin
87

A dental patient presents with signs and symptoms of anemia; petechiae, ecchymoses, and gingival bleeding. What is the correct course of action?

They should be referred to a physician for evaluation, diagnosis, and treatment as indicated.

88

Why should special emphasis should be placed on oral hygiene procedures in patients with sickle cell anemia?

To avoid development of dental caries, gingival inflammation, and infection, which can lead to osteomyelitis.

89

What are five oral manifestations of nutritional deficiency anemias (e.g. vitamin B12, folate, or iron)?

  1. smooth, red tongue (loss of papillae)
  2. atrophic changes in the oral mucosa
  3. angular cheilitis and aphthae
  4. burning or sore tongue
  5. Plummer-Vinson syndrome
90

Which nutritional deficiency anemia is associated with Plummer-Vinson syndrome?

iron deficiency anemia

91

Iron deficiency anemia is associated with Plummer-Vinson syndrome. What are the three characteristics of PVS?

  1. sore mouth
  2. dysphagia (esophageal “webbing”)
  3. increased oropharyngeal carcinoma
92
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What about this barium contrast radiograph indicates a diagnosis of iron deficiency anemia?

It is showing esophageal webbing, characteristic of Plummer-Vinson syndrome.

93

Which types of anemia are associated with changes in trabecular bone on dental radiographs?

hemolytic anemias

94

What four bone changes are observed on dental radiographs in hemolytic anemias?

  1. enlarged medullary spaces
  2. widened trabeculations
  3. generalized osteoporosis
  4. increased radiolucency
95
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What about this dental radiograph indicates a diagnosis of hemolytic anemia?

Because of compensatory marrow expansion, the bone appears radiolucent with horizontal lamellar striations between the teeth in a “stepladder” configuration.

96
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What about this skull radiograph indicates a diagnosis of hemolytic anemia?

There is new bone formation on the outer table, producing perpendicular radiations or “hair on end” appearance.

97

What are four oral findings commonly associated with aplastic anemia?

  1. petechiae and ecchymoses
  2. mucosal pallor
  3. ulceration (infection)
  4. gingival bleeding and hyperplasia
98
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What about this patient presentation suggests a diagnosis of aplastic anemia?

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There is diffuse gingival hyperplasia and gingival bleeding.