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Project - USMLE Step 3 > Symptom To Diagnosis - Anemia > Flashcards

Symptom To Diagnosis - Anemia Flashcards

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USMLE® Step 1 flashcards
1
Q

First step in determining the cause of anemia?

A

Determine the general mechanism of the anemia, using a PATHOPHYSIOLOGIC framework.

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2
Q

After determining the general mechanism, what is the next step in the DDx of anemia?

A

The next step is to determine the cause of the underproduction, hemolysis, or blood loss.

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3
Q

The framework of underproduction in the DDx of anemia is?

A

Morphologic.

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4
Q

Microcytic anemias:

A

MCV < 80.

  1. Iron def.
  2. Thalassemia.
  3. Anemia of inflammation (formerly called anemia of chronic disease).
  4. Sideroblastic anemia.
  5. Lead exposure.
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5
Q

Macrocytic anemias?

A

MCV > 100.

  1. Megaloblastic anemias (due to abnormalities in DNA synthesis; hypersegmented neutrophils).
    a. B12.
    b. Folate.
    c. Antimetabolite drugs, such as methotrexate and zidovudine.
  2. Nonmegaloblastic anemias (no hypersegmented neutrophils).
    a. Alcohol abuse.
    b. Liver disease.
    c. Hypothyroidism.
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6
Q

Normocytic anemias?

A
  1. Anemia of inflammation.
  2. Early iron def.
  3. Infiltration of bone marrow due to malignancy or granulomas.
  4. RBC aplasia
    a. Aplastic anemia.
    b. Suppression by medication or parvovirus B19.
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7
Q

Hereditary hemolytic anemias:

A
  1. Enzyme deficiencies - G6PD.
  2. Hemoglobinopathies - such as sickle cell.
  3. RBC membrane abnormalities, such as spherocytosis.
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8
Q

Acquired hemolytic anemias?

A
  1. Hypersplenism.
  2. Immune:
    a. Autoimmune: warm IgG, cold IgM, cold IgG.
    b. Drug-induced: autoimmune or hapten.
  3. Traumatic –> Impact/ Macrovascular (prosthetic valves)/ Microvascular (DIC, TTP, HUS)
  4. Infections (malaria, babesiosis).
  5. Toxins, such as snake venom and aniline dyes.
  6. Paroxysmal nocturnal hemoglobinuria.
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9
Q

Diagnostic approach of anemia - 1st step.

A

Check WBC, platelet count, smear.
Pancytopenia?
Yes –> Consider bone marrow process.
No –> Isolated anemia.

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10
Q

Diagnostic approach of anemia - Isolated anemia is found. Next step?

A

Check Reticulocyte production index.
If >2 –> Increased destruction (Hemolysis).
If Underproduction.

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11
Q

Diagnostic approach to anemia - Underproduction is found. Next step?

A

Check MCV.

Low-Normal-High –> Micro-Normo-Macro.

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12
Q

Diagnostic approach of anemia - MCV is low or normal. Next step?

A

Check ferritin.
If low –> Dx: Fe def. - Determine source.
If normal-high –> Check creatine, B12, folate, TSH, consider thalassemia.

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13
Q

Diagnostic approach of anemia - High MCV is found?

A

Check B12, folate, TSH, alcohol, and drug history.

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14
Q

Symptoms in chronic anemia are due to decreased?

A

Deceased O2 delivery to the tissues.

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15
Q

Symptoms in chronic anemia?

A
  1. Fatigue - Common, but NOT very specific.
  2. Dyspnea on exertion often.
  3. Exertional chest pain - In patients with underlying coronary artery disease or SEVERE anemia or BOTH.
  4. Palpitations and tachycardia can occur.
  5. EDEMA is sometimes seen.
  6. ASYMPTOMATIC if mild.
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16
Q

Edema in chronic anemia. Explain.

A
  1. Due to decreased renal blood flow –> leading to neurohormonal activation and salt and water retention, similar to CHF.
  2. HOWEVER - High cardiac output in anemia.
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17
Q

Symptoms of Hypovolemia in anemia?

A

Occur only in acute anemia due to large volume blood loss.

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18
Q

LR+ of conjunctival rim pallor for anemia?

A

16.7 –> Strongly suggests that the patient is anemic.

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19
Q

LR+ of palmar crease pallor in anemia?

A

7.9.

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20
Q

LR+ for pallor elsewhere (nail beds, facial) in anemia?

A

<5, not as useful.

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21
Q

Physical sign rules that out anemia?

A

None.

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22
Q

Overall sensitivity and specificity of the physical exam for anemia is about?

A

70%.

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23
Q

When to order a CBC for anemia?

A
  1. If the patient has suggestive symptoms, even WITHOUT physical findings.
  2. Or if you observe conjunctival rim or palmar crease pallor.
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24
Q

What is the importance of looking at a previous CBC?

A

To see if the current anemia is old, new, or progressive.

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25
Q

The best way to distinguish underproduction from hemolysis?

A

The Reticulocyte count.

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26
Q

Low or normal Reticulocyte count?

A

In underproduction anemias.

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27
Q

High Reticulocyte count?

A

When the bone marrow is responding normally to blood loss, hemolysis, or replacement of iron, B12, folate.

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28
Q

Reticulocyte count?

A

Percentage of circulating RBCs that are reticulocytes (normally 0.5-1.5%).

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29
Q

Absolute Reticulocyte count?

A

The NUMBER of reticulocyte actually circulating, normally 25.000-75.000/mcL - Multiply the percentage of reticulocytes by the total number of RBCS.

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30
Q

The Reticulocyte production index (RPI)?

A

Corrects the reticulocyte count for the degree of anemia and for the prolonged peripheral maturation of reticulocytes that occurs in anemia.

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31
Q

Normal maturation of reticulocytes?

A

First 3-3.5 days occur in the bone marrow and the last 24hr in the peripheral blood.

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32
Q

For a Hct of 25%, what is the peripheral blood maturation time of reticulocytes?

A

2 days. (2.5 days for Hct 15%).

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33
Q

Importance of MCV in the diagnostic approach of anemia?

A

MCV is NOT specific and should NOT be used to rule in or rule out a specific cause of anemia.

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34
Q

Percentage of patients with ABNORMAL serum B12, folate and iron, that have NORMAL MCV?

A

50%, in one study.

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35
Q

High MCV in iron def anemia?

A

5%.

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36
Q

Low MCV in B12 or folate def.?

A

12%.

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37
Q

Bottom line about MCV?

A

Use MCV to organize your thinking, NOT to diagnose the cause of an anemia.

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38
Q

Pretest probability for Fe def anemia in a patient with microcytic anemia and symptoms suggestive chronic blood loss?

A

80%.

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39
Q

Iron def. Anemia - Textbook presentation.

A

Young, menstruating woman who has fatigue and a craving for ice.
Typical presentations include fatigue, dyspnea, and sometimes EDEMA.

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40
Q

In very early iron deficiency, the CBC is?

A

Normal.

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41
Q

Iron def. - etiology:

A
  1. MCC is blood loss, most commonly menstrual or GI.
  2. Inadequate intake.
  3. Malabsorption seen in patients with gastrectomy, some bariatric procedures, celiac sprue, or IBD.
  4. Increased demand seen in pregnancy, infancy, adolescence, EPO therapy.
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42
Q

Gold standard exam for iron def?

A

Bone marrow exam for absence of iron stores.

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43
Q

Best SERUM test for iron def?

A

Serum ferritin.

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44
Q

What is the LR+ for a decreased serum ferritin in anemia?

A

Very high, ranging from 51 for a ferritin Low ferritin rules IN iron def. anemia.

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45
Q

What is the LR- for a serum ferritin >100ng/mL in the general population?

A

It is very low - 0.08.

–> In the general population, a ferritin >100ng/mL greatly reduces the probability the patient has iron def.

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46
Q

What is the main problem with ferritin?

A

It is ALSO an acute phase reactant –> Interpretation in the presence of inflammation is difficult.

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47
Q

Is ferritin helpful in diagnosing iron def. in the presence of inflammation?

A

There is a wide range of reported LRs, with many studies finding ferritin is NOT helpful in diagnosing iron deficiency in the presence of chronic illness.

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48
Q

To sum up, can ferritin be used to absolutely rule in or rule out iron def. anemia in patients with chronic inflammatory disease?

A

NO.

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49
Q

MCV, transferrin saturation (serum Fe/TIBC), red cell protoporphyrin, red cell ferritin, and RDW compared to ferritin?

A

ALL are LESS sensitive and specific compared to ferritin.

–> The best of these is transferrin saturation <5% with a LR+ of 10.46.

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50
Q

Treatment of iron def. anemia?

A

Oral iron replacement, with IV iron therapy reserved for patients who demonstrate malabsorption or who are unable to tolerate oral iron.

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51
Q

Best absorbed oral iron?

A

Ferrous sulfate - dose is 325mg 3x/day.

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52
Q

Transfusion in iron def. anemia?

A

Only if the patient is:

  1. HYPOTENSIVE.
  2. Orthostatic.
  3. Actively bleeding.
  4. Angina.
  5. Dizziness.
  6. Syncope.
  7. SEVERE dyspnea/fatigue.
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53
Q

GI effects of iron therapy?

A

SIGNIFICANT:

  1. Nausea.
  2. Abdominal pain.
  3. Constipation.
    - -> Can be reduced by taking iron with food, and slowly titrating the dose from 1 tablet daily to 3 tablets over 1-2wks.
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54
Q

Increase in reticulocytes/Hb/Hct after iron therapy?

A

There should be an increase after 7-10 days, and an increase in Hb and Hct by 30 days.
–> If NO RESPONSE, reconsider the diagnosis.

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55
Q

How long should someone take iron in order to replete iron stores?

A

6 MONTHS.

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56
Q

What is important to keep in mind in iron def. anemia?

A

ALWAYS IDENTIFY THE SOURCE OF BLOOD LOSS.

Be alert for occult malignancies.

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57
Q

Who needs a GI work-up in order to identify the source of iron def.?

A
  1. All men, all women without menorrhagia, and women over age 50 even with menorrhagia.
  2. Women under age 50 with menorrhagia do NOT need further GI evaluation, unless they have GI symptoms or a family history of early colon cancer or adenomatous polyps.
  3. Alway ask carefully about minimal GI symptoms in young women, since celiac sprue often causes iron def. due to malabsorption, and the symptoms can easily be attributed to IBS.
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58
Q

In order to identify the source of iron def. anemia, which GI test should be done first?

A
  1. In the absence of symptoms or in the presence of lower GI symptoms, do a COLONOSCOPY first.
  2. If there are upper GI symptoms, do an esophagogastroduodenoscopy (EGD) first.
  3. If the 1st test is negative, the other must be done.
  4. Small bowel RARELY has problems - can be omitted.
  5. If EGD shows a definitive bleeding source –> Colonoscopy can be reserved for SYMPTOMATIC patients or those who need routine colorectal cancer screening.
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59
Q

Pretest probability of B12/folate deficiency with an MCV of 115-129mcm^3?

A

50%.

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60
Q

Pretest probability of B12/folate def. with an MCV>130mcm^3?

A

Nearly ALL patient with an MCV>130 will have a vit. def.

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61
Q

Textbook presentation of B12 def?

A

An elderly woman with marked anemia and neurologic symptoms such as paresthesias, sensory loss (especially vibration and position), ataxia, dementia, and psychiatric symptoms.

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62
Q

Is anemia and macrocytosis always present in B12 def.?

A

NO - In 1 study –> 28% of patients with neurologic symptoms due to B12 deficiency had no anemia or macrocytosis.

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63
Q

In another study, what clinical characteristics were found in patients with B12 def.?

A 
33% white, 41% black, 25% latino.
28% NOT anemic.
17% NORMAL MCV.
17% leukopenia.
35% thombocytopenia.
12.5% pancytopenia.
36% neuropsychiatric symptoms.
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64
Q

Important point about B12 def.?

A

The CBC can be NORMAL in B12 def.

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65
Q

MCC of B12 def?

A
  1. Food cobalamin malabsorption.
  2. Lack of intrinsic factor.
  3. Dietary deficiency - rare unless the patient follows a vegan diet.
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66
Q

Food cobalamin malabsorption due to impaired acid peptic digestion?

A
  1. B12 in this condition is often subclinical.
  2. It is caused by atrophic gastritis and achlohydria, which can be seen with chronic H.pylori infection, gastric surgery, long-term use of acid suppressing drugs.
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67
Q

Lack of intrinsic factor is caused by?

A
  1. Gastrectomy - ALL with total, and 5% with partial –> Become B12 def.
  2. Pernicious anemia.
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68
Q

PA is?

A

An immunologically mediated gastric atrophy leading to loss of parietal cells and a marked reduction in secretion of IF.

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69
Q

PA is uncommon?

A

Before age 30 and most often seen in patients over age 50.

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70
Q

History in PA?

A

25% will have a family history of PA.

10% will have autoimmune thyroid disease.

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71
Q

B12 def. due to malabsorption in the terminal ileum?

A
  1. Ileal resection or bypass.
  2. Tropical sprue.
  3. Crohn.
  4. Blind loop syndrome.
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72
Q

Drugs that interfere with B12 absorption?

A

Most notably:

  1. Metformin.
  2. Colchicine.
  3. Ethanol.
  4. Neomycin.
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73
Q

Rare cause of B12 def.?

A

Due to congenital disorders, such as transcobalamin II deficiency.

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74
Q

Why determining whether the patient is B12 deficient is more complicated than it seems?

A
  1. B12 levels can be falsely in folate def., pregnancy, and OCP use.
  2. B12 can be falsely normal in myeloproliferative disorders, liver disease, and bacterial overgrowth syndromes.
  3. Sensitivity/Specificity of B12 levels for true deficiency are NOT well established - Estimated sensitivity is 95% and specificity is 85%.
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75
Q

B12 is a cofactor for what?

A
  1. Conversion of MMA to succinyl CoA.
  2. Conversion of homocysteine to methionine.
    B12 def –> Increase MMA + Homocysteine.
76
Q

In addition to B12 def. MMA can be elevated in?

A
  1. Renal insufficiency.

2. Hypovolemia.

77
Q

Homocysteine can be elevated in?

A
  1. Folate or pyridoxine deficiency.
  2. Renal insufficiency.
  3. Hypovolemia.
  4. Hypothyroidism.
78
Q

Sensitivity of MMA for the diagnosis of B12 def.?

A

86-98%.

79
Q

Sensitivity of homocysteine for the diagnosis of B12 def.?

A

85-96%.

80
Q

MMA or homocysteine more specific for the diagnosis of B12 def.?

A

MMA in the absence of renal insufficiency.

81
Q

Another way to establish B12 def.?

A

Response to therapy.

82
Q

MMA and homocysteine will normalize when after the beginning of B12 replacement therapy?

A

7-14days.

83
Q

Algorithm for diagnosing B12 def?

A
  1. B12 Check MMA and homocysteine.
    a. If BOTH normal –> Def. is unlikely.
    b. If BOTH elevated –> Def. is present.
    c. If MMA elevated –> Def. is present.
    d. If homocysteine –> Def. is possibly present.
  2. B12 >300pg/mL –> Def. is unlikely.
84
Q

Bottom line about B12 levels?

A

Very low or very high B12 levels are usually diagnostic.

85
Q

Treatment of B12 def?

A
  1. IM cobalamin, 1000mg weekly for 6-8weeks, and then MONTHLY for life.
  2. Also, ORAL cobalamin, 1000-2000mg DAILY.
  3. Sublingual and intranasal formulations are available but have NOT been exclusively studies.
86
Q

Oral cobalamin?

A
  1. It is absorbed by a 2nd, NON INTRINSIC FACTOR DEPENDENT mechanism that is relatively insufficient.
  2. Patients with dietary deficiency and food cobalamin malabsorption can be treated with lower doses of oral B12.
87
Q

Main problem with oral cobalamin?

A

Compliance. (daily).

88
Q

Textbook presentation of folate deficiency?

A

Alcoholic patient with malnutrition and anemia.

89
Q

MCC of folate?

A

Inadequate intake (especially in alcoholics) or increased demand due to pregnancy, chronic hemolysis, leukemia.

90
Q

Why is malabsorption of folate rare?

A

Because absorption occurs in the jejunum –> Rare in the absence of short bowel syndrome or bacterial overgrowth syndromes.

91
Q

Drugs that can cause folate def.?

A
  1. Methotrexate.
  2. Phenytoin.
  3. Sulfasalazine.
  4. Alcohol.
92
Q

Folate is cofactor in?

A

Conversion of homocysteine to methionine –> Homocysteine UP in folate def.

93
Q

Sensitivity/Specificity of serum folate measurements for the diagnosis of folate def.?

A

Not clear.

94
Q

Variations in folate levels?

A
  1. Can DECREASE within a few days of dietary folate restriction, or with alcohol use, even though tissue stores can be normal.
  2. Levels increase with feeding.
95
Q

RBC folate?

A

Reflects folate status over the previous 3 months –> Correlates more strongly with megaloblastic changes than does serum folate.

96
Q

RBC folate sensitivity/specificity for the diagnosis of true deficiency?

A

Both low - 70%.

97
Q

Homocysteine sensitivity/specificity for the diagnosis of folate def.?

A

Sensitivity –> About 80%.

Specificity –> Unknown.

98
Q

Folate def. - Positive response to therapy is?

A

Diagnostic.

–> NEVER treat without determining whether the patient is B12 deficient –> Neurological problems will continue.

99
Q

A patient with normal serum folate, normal RBC folate, and no response to folate replacement?

A

Does NOT have folate deficiency!

100
Q

Folate def. treatment?

A
  1. Acute def. –> 1mg folic acid daily for 1-4 months, or until there is complete hematologic recovery.
  2. Chronic def. –> 1mg folate daily indefinitely.
101
Q

Folate treatment in women who are trying to conceive?

A

800mg/Daily or a prenatal vitamin (contains 1mg of folate).

102
Q

Pregnant women - Folate treatment?

A

Should take a prenatal vitamin (1mg folate).

103
Q

B12 def. due to malabsorption - Possible sites?

A
  1. Stomach.

2. Ileum.

104
Q

Stomach - B12 malabsorption:

A
  1. Gastrectomy or gastric bypass.
  2. Detectable anti-intrinsic factor antibody.
  3. Anti-parietal antibodies.
105
Q

Anti-intrinsic factor antibodies - Found in?

A

50-80% of patients with PA –> Presence rules IN/ Absence does NOT rule OUT.

106
Q

Antiparietal cell antibodies - Found in?

A

85% of PA patients - BUT also, in other autoimmune endocrinopathies and 10% of NORMAL patients.
–> Presence does NOT rule IN PA.

107
Q

Bottom line about the cause of B12 def.?

A

It is NOT ALWAYS possible to determine the site of malabsorption, and it is generally acceptable to treat such patients empirically with B12 replacement.

108
Q

Anemia of inflammation - Textbook presentation:

A

Because there is such a broad spectrum of underlying causes, there is NO CLASSIC presentation of anemia of inflammation.
Most often discovered on a routine CBC that shows a normochromic, normocytic anemia, with a Hb in the range of 8.5-9.5 g/dL.

109
Q

Main mechanism of anemia of inflammation?

A

Cytokines (interferons, interleukins, TNF,) induce changes in iron homeostasis.

110
Q

What changes in iron homeostasis do cytokines induce?

A
  1. Dysregulation of iron homeostasis.
    a. Incr. uptake and retention of iron in reticuloendothelial system cells.
    b. Limited availability of iron for erythropoiesis.
  2. Impaired proliferation and differentiationnn of erythroid progenitor cells.
  3. Blunted EPO response.
    a. Inadequate EPO production.
    b. Progenitor cells do NOT respond normally.
  4. Incr. erythrophagocytosis –> Decreased RBC half-life.
111
Q

Underlying causes of anemia of inflammation?

A
  1. Chronic kidney disease.
  2. Autoimmune diseases - SLE, RA, vasculitis, sarco, IBD.
  3. Acute infections - Viral, bacterial, fungal, parasites.
  4. Chronic infections - Viral, bacterial, fungal, parasites.
  5. Cancer either hematologic or solid tumor.
112
Q

Anemia in CKD?

A
  1. If ESRD –> Anemia is due to lack of EPO and marked inflammation.
  2. If lesser CKD –> Anemia is due to lack of EPO + antiproliferative effect of uremic toxins.
113
Q

Anemia due to ACUTE infections?

A
  1. Can occur within 24-48hrs in acute bacterial infections - Hb usually in the 10-12g/dL range.
  2. Occurs in as many as 90% of ICU patients - Accompanied by inappropriately mild elevations of serum EPO levels + Blunted marrow response to endogenous EPO.
114
Q

Non-inflammatory chronic anemias?

A

A. Endocrinopathies –> Such as Addison, thyroid disease, panhypopituitarism can lead to mild chronic anemia.
B. Liver disease can cause anemia.

115
Q

Is there a single test that proves or disproves a patient’s anemia is from anemia of inflammation?

A

NO.

116
Q

A Hb <8g/dL suggests?

A

There is a 2nd cause for the anemia, beyond the anemia of inflammation.

117
Q

Even in the presence of a disease known to cause anemia, it is important to rule OUT?

A

Iron, B12, folate deficiencies.

118
Q

Typical lab findings in anemia of inflammation?

A
  1. Low serum iron.
  2. Low TIBC.
  3. Normal saturation.
  4. Elevated ferritin.
119
Q

EPO measurement in anemia of inflammation?

A

Interpretation is difficult and EPO level is usually NOT useful diagnostically.

120
Q

When you see pancytopenia?

A
  1. Bone marrow infiltration.
  2. B12.
  3. Viral infection.
  4. Drugs toxicity.
  5. Acute alcohol intoxication.
121
Q

Bone marrow exam is necessary when in the diagnostic process of anemia of chronic disease?

A
  1. When pancytopenia is present.
  2. Serum tests are not diagnostic.
  3. The anemia progresses.
  4. There is NOT an appropriate response to empiric therapy.
122
Q

Anemia of inflammation - Treatment?

A

Treat the underlying chronic disease, if possible.

123
Q

Anemia of inflammation - EPO treatment?

A

Indications for EPO therapy and appropriate target Hb levels are EVOLVING - IRON should be given to all patients being treated with EPO.

124
Q

In what settings are the RBC destroyed in the INTRAvascular space?

A

In the setting of impact, macrovascular, or microvascular trauma, and some complement-induced lysis.

125
Q

Damaged but incompletely hemolyzed cells?

A

Are destroyed in the spleen.

126
Q

Hemoglobinuria in intravascular hemolysis?

A

Some Hb is lysed intravascularly and then is filtered by the glomerulus –> Hemoglobinuria.

127
Q

Hemosiderinuria in intravascular hemolysis?

A

Some filtered Hb is taken up by the renal tubular cells, stored as hemosiderin, and hemosiderinuria occurs about a WEEK LATER, when the tubular cells are sloughed into the urine.

128
Q

Deformed RBCs or those coated with complement are usually destroyed in?

A

The EXTRAvascular space, in the liver or in the spleen.

129
Q

In extravascular hemolysis, what is the fate of Hb?

A

It is degraded into biliverdin, iron, and carbon monoxide.

  • -> Biliverdin is converted to unconjugated bilirubin and released into the plasma –> Increasing the unconjugated bilirubin level.
  • -> Some FREE Hb is released –> Binds haptoglobin.
130
Q

Reticulocyte in hemolytic anemias?

A

4-5% - In one study of autoimmune hemolytic anemia, the median was 9%.

131
Q

Serum haptoglobin in hemolytic anemias?

A

Should be <25mg/dL.

132
Q

Sensitivity/Specificity, LR+/- of haptoglobin in hemolytic anemia?

A

Sensitivity 83%.
Specificity 96%.
LR+ =21.
LR- =0.18.

133
Q

What is haptoglobin?

A

An acute phase reactant.

134
Q

Sensitivity/Specificity of LDH in hemolytic anemia?

A

UNKNOWN - Might be increased.

135
Q

Finding an increased LDH + a decreased haptoglobin is?

A

90% specific for the diagnosis of hemolysis.

136
Q

Finding a normal LDH + a normal haptoglobin (>25mg/dL) is 92% sensitive for?

A

The absence of hemolysis.

137
Q

Unconjugated bilirubin sensitivity/specificity in hemolytic anemia?

A

UNKNOWN - May be increased.

138
Q

Sensitivity/Specificity of plasma and urine Hb in INTRAVASCULAR hemolysis?

A

UNKNOWN - Should be increased.

139
Q

Treatment of TTP and HUS?

A

Plasmapheresis and immunosuppressive.

140
Q

Questions in order to find the cause of hemolytic anemia?

A
  1. Does the patient have splenomegaly? –> Extravascular hemolysis.
  2. Coombs (+)?
  3. Concomitant thrombocytopenia and coagulopathy? –> DIC.
  4. Concomitant thrombocytopenia, renal insufficiency, or neurologic symptoms? –> TTP/HUS.
  5. Schistocytes? –> Traumatic hemolysis macro/microvascular.
  6. Exposed to infection/drug/toxin known to cause hemolysis?
  7. Mechanical valve?
  8. Known disease associated with hemolytic anemia?
141
Q

Sickle cell anemia - Textbook presentation?

A
  1. SCA is often identified at birth through screening.
  2. Adult patients generally seek medical attention for pain or some of the complications.
  3. Occasionally, patients have very mild disease, and sickle cell is diagnosed late in life when evidence of a specific complication (eg sickle cell retinopathy) is identified.
142
Q

Gene frequency for SCA or thalassemia is … of non-Hispanic white births?

A

0.17%.

143
Q

Gene frequency of HbS, HbC, and of beta-thal in African-Americans?

A

HbS –> 4%.
HbC –> 1.5%.
Beta-thal –> 4%.

144
Q

SCA - Median age of death for men and women?

A

Men –> 42.

Women –> 48.

145
Q

Risk factors for earlier mortality in SCA?

A
  1. Lower HbF levels.
  2. Episodes of acute chest syndrome.
  3. More frequent pain crises.
  4. Possibly higher WBC.
146
Q

Clinical manifestations of SCA - Hematologic?

A
  1. Ht 20-30%, reticulocyte count 3-15%.
  2. MCV usually normal high or high.
  3. UCB, UP LDH, DOWN haptoglobin.
  4. HbF usually slightly elevated.
  5. WBC and platelet count usually elevated.
  6. Hypercoagulability.
147
Q

Hypercoagulability in SCA?

A
  1. High levels of thrombin.
  2. Low levels of protein C/S.
  3. Abnormal activation of fibrinolysis and platelets.
148
Q

Clinical manifestations of SCA - Pulmonary?

A
  1. Acute chest syndrome.

2. Sickle cell chronic lung disease.

149
Q

Acute chest syndrome - Definition?

A

New pulmonary infiltrate accompanied by fever and a combination of respiratory symptoms, including cough, dyspnea, and chest pain.

150
Q

MCC of death in SCA?

A

Acute chest syndrome.

151
Q

Acute chest syndrome - Clinical manifestations in adults?

A
  1. About 50% of patients in whom acute chest syndrome develops are admitted for another reason.
  2. Over 80% have concomitant pain crises.
  3. Up to 25% require mechanical ventilation.
152
Q

Acute chest syndrome - Etiology?

A
  1. Fat embolism - from infarction of long bones, with or without infection in 12%.
  2. Infection in 27%, with 8% due to bacteria, 5% due to Mycoplasma, 9% chlamydia.
  3. Infarction in about 10%.
  4. Hypoventilation and atelectasis due to pain and analgesia may play a role, as might fluid overload.
  5. UNKNOWN in about 50% of patients.
153
Q

Acute chest syndrome - General principles of management?

A
  1. Supplemental O2.
  2. Empiric treatment with a macrolide and a cephalosporin.
  3. Incentive spirometry (can be preventive).
  4. Bronchodilators in patients with reactive airways.
  5. Transfusion.
154
Q

MC clinical features of acute chest syndrome in adults?

A 
81% --> Crackles.
70% --> Fever.
59% --> Limb pain.
58% --> Shortness of breath.
55% --> Chest pain and cough.
Mean TEMPERATURE = 38.8
155
Q

Percentage of patients with SCA that have reactive airways?

A

35-60%.

156
Q

Sickle cell chronic lung disease - Restrictive or Obstructive?

A

About 20% have restrictive.

About 20% have mixed.

157
Q

SC chronic lung disease - PHTN?

A

Up to 40%.

158
Q

RR of death in sickle cell patients with PHTN, compared with those with normal pulm. pressures?

A

10.

159
Q

Clinical manifestations of SCA - Renal?

A
  1. Hyposthenuria - inability to concentrate urine - Max osmolality of 400-450 mOsm/kg.
  2. RTA type 4.
  3. Hematuria - Usually due to papillary necrosis (renal medullary carcinoma has been reported).
  4. Proteinuria.
160
Q

Clinical manifestation of SCA - Proteinuria?

A
  1. Seen in 20-30% of patients with SCA - About 4% have nephrotic syndrome.
  2. Progresses to chronic renal failure in about 5% of patients.
  3. ACEIs reduce proteinuria.
161
Q

Clinical manifestations of SCA - Priapism?

A
  1. 30-40% of adult males with SCA report at least 1 episode.
  2. Bimodal peak incidences in ages 5-13 and 21-29.
  3. 75% of episodes occur during sleep - Mean duration is 125min.
162
Q

Clinical manifestations of SCA - Priapism - Treatment?

A
  1. Hydration.
  2. Analgesics.
  3. Injection.
  4. Alpha-adrenergic drugs.
163
Q

Clinical manifestations of SCA - Neurologic?

A
  1. 1st infarction usually between 2-5yrs, followed by another peak incidence between 35-45.
  2. Hemorrhagic stroke can also occur.
  3. Recurrent infarction occurs in 67% of patients.
  4. Silent infarction is common (seen in 18-23% of patient by age 14) - cognitive deficits are common.
  5. Patients over 2 yrs of age should undergo annual transcranial Doppler to assess stroke risk.
164
Q

TCD screening in SCA - Which patients are at risk for a stroke?

A

Patients with elevated TCD velocities (>200cm/s) are at high risk.

165
Q

Clinical manifestations of SCA - Musculoskeletal?

A
  1. Bones and joints often the sites of VASO-OCCLUSIVE episodes.
  2. Avascular necrosis of the hips, shoulders, ankles, spine –> Chronic pain –> Best detected by MRI, may require joint replacement.
166
Q

SCA retinopathy?

A
  1. More common in patients with HbSC disease than with SS disease.
  2. Treated with photocoagulation.
167
Q

SCA - Leg ulcers?

A
  1. Present in about 20% of patients.

2. Most commonly over the medial and lateral malleoli.

168
Q

SCA - Cholelithiasis?

A

Nearly universal due to chronic hemolysis.

169
Q

SCA - Spleen?

A

Splenic sequestration and autosplenectomy - seen in children.

170
Q

SCA - Liver disease?

A

Multifactorial, due to causes such as iron overload or viral hep.

171
Q

SCA - Newborn screening?

A
  1. Universal screening identifies many more patients than screening targeted at high-risk groups.
  2. Homozygotes have an FS pattern on electrophoresis, which is predominantly HbF, with some HbS, and NO HbA.
  3. The FS pattern is NOT SPECIFIC for SCA disease - The diagnosis should be confirmed through family studies, DNA based testing, or repeat Hb electrophoresis at 3-4 months of age.
172
Q

SCA - Testing in older children and adults?

A
  1. Cellulose acetate electrophoresis separates HbS from other variants; however, S, G, and D all have the same electrophoretic mobility.
  2. Only HbS will precipitate in a solubility test such as the Sickledex.
173
Q

SCA - Treatment - General principles?

A
  1. All pediatric patients should receive prophylactic penicillin to prevent streptococcal sepsis.
  2. Transfusion in specific cases.
  3. Hydroxyurea.
  4. Stem cell transplant is experimental.
174
Q

SCA - Transfusion indications?

A
  1. Acute chest syndrome.
  2. Heart failure.
  3. Multiorgan failure syndrome.
  4. Stroke.
  5. Splenic sequestration.
  6. Aplastic crisis.
175
Q

SCA - Transfusion guidelines?

A
  1. Do not transfuse above an Hb of about 11g/dL to avoid hyperviscosity.
  2. Use simple transfusion if Hb is below 8g/dL.
  3. Use exchange transfusion if Hb above 8g/dL.
176
Q

SCA Treatment - Hydroxyurea?

A
  1. In moderate/severe SCA hydroxyurea therapy reduced the rate of pain crises and development of acute chest syndrome by about 50%.
  2. Hydroxyurea use is associated with a lower mortality rate.
177
Q

SCA Treatment - Management of vaso-occlusive crises?

A
  1. General approach should be similar to that used in patients with other causes of severe pain, such as cancer.
  2. Oral hydration is preferable to IV hydration.
  3. O2 is indicated only if the patient is hypoxemic.
178
Q

Beta-thal textbook presentation?

A

Beta-thal major (homozygotes) presents in infancy with multiple severe abnormalities.
Heterozygotes are usually symptomatic.

179
Q

Beta-thal disease highlights?

A
  1. Impaired production of beta globin chains.
  2. Common in Mediterranean origin.
  3. Beta-thal minor: heterozygotes with 1 normal beta globin allele and 1 beta thalassemic allele.
  4. Anemia generally mild (Ht>30%) and SEVERE microcytosis (MCV<75).
  5. In pregnancy, anemia can be more severe than usual.
  6. Asymptomatic splenomegaly in 15-20% of patients.
180
Q

Beta-thal evidence based diagnosis?

A
  1. Iron studies should be normal.
  2. RDW usually normal.
  3. Abundant target cells.
  4. RBCs may be normal or high.
  5. HbA2 elevated, but a NORMAL HbA2 does NOT rule out beta-thal minor.
181
Q

Treatment of beta-thal minor?

A

None.

182
Q

Alpha-thal textbook presentation?

A
  1. Loss of 3 or 4 alpha globin genes causes severe disease that presents at birth or is fatal in utero.
  2. Patients with loss of 1 or 2 genes are usually asymptomatic.
183
Q

Alpha-thal - Disease highlights?

A
  1. Impaired production of alpha-globin chains.
  2. Common in patients of African or Asian origin.
  3. Alpha-thal-2 trait: Loss of 1 alpha globin gene - CBC normal.
  4. Alpha-thal-1 trait (alpha-thal minor): Loss of 2 alpha globin genes –> MILD microcytic anemia with target cells and normal Hb electrophoresis.
184
Q

Alpha-thal - Diagnosis?

A

By PCR genetic analysis.

185
Q

Treatment of alpha-thal trait?

A

None.

186
Q

Framework of organizing DDx for anemia?

A

Pathophysiologic + Morphologic.

Project - USMLE Step 3 (82 decks)

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