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

Symptom To Diagnosis - AIDS Flashcards

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USMLE® Step 1 flashcards
1
Q

HIV - common modes of transmission:

A

62% –> male to male sexual transmission.
17% –> needle sharing among injection drug users.
13% –> heterosexual transmission.
+ vertical transmission from mother to child.

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2
Q

Current risk associated with blood transfusion for HIV 1 and 2:

A

1/1.800.000

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3
Q

The highest risk of sexual transmission is among patients with:

A
  1. Unprotected receptive anal intercourse.
  2. Sex for hire workers.
  3. Sexual contacts of sex for hire workers.
  4. Individuals with multiple sexual partners.
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4
Q

CD4 count in chronic HIV infection:

A

There is a very slowly progressive disease in the CD4 T cell count in the blood –> 2 BILLION cells destroyed every and replaced every day.
BOTH infected and NONinfected CD4 T cells are activated and destroyed.

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5
Q

Stages of HIV infection:

A
  1. Viral transmission.
  2. Primary infection.
  3. Seroconversion.
  4. Clinically latent period.
  5. Early symptomatic HIV infection.
  6. AIDS and advanced HIV infection.
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6
Q

Similar to any other diagnosis, the PPV in HIV diagnosis is determined by?

A

3 factors:

  1. Pretest probability.
  2. Sensitivity.
  3. Specificity.
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7
Q

Estimating pretest probability in HIV infection:

A
  1. Risk factors: MSM, injection drug abuse, multiple sexual partners.
  2. Prevalence of HIV infection - Varies from 0.3% in the US to >50% in certain high risk groups.
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8
Q

False(+) results in HIV EIA testing:

A
  1. Recent influenza.
  2. Hep B immunization.
  3. DNA virus infection.
  4. Increasing parity.
  5. PRP (+).
  6. Improper heating.
  7. Clerical error.
  8. HIV vaccine.
  9. Cross reacting antibody.
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9
Q

False (-) results in HIV EIA testing:

A
  1. Recent HIV infection prior to development of antibodies (window period) - Seroconversion occurs sometime between 10days to 6 weeks.
  2. Rare causes –> Advanced AIDS with swro-REVERSION, immunosuppression therapy, malignancy, bone marrow transplant, B cell dysfunction, replacement transfusion, hypogammaglobulinemia, infection by rare HIV types.
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10
Q

Western blot testing for HIV - Positive results require:

A

At least 2 of the following 3 bands:

  1. gp160/120.
  2. gp41.
  3. p24.
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11
Q

Western blot testing for HIV - Negative results require:

A

The ABSENCE OF ANY visible bands.

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12
Q

Indeterminate results in HIV diagnosis:

A

Occurs in 10-15% of cases.

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13
Q

3 pivotal considerations help frame the DDX:

A
  1. Acuity of symptoms.
  2. Degree of immunosuppression.
  3. Mass lesion on neuroimaging.
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14
Q

DDx of headache in patient with HIV - Meningoencephalitis:

A
  1. Cryptococcal meningitis.
  2. HIV encephalopathy.
  3. CMV ventriculoencephalitis.
  4. TB meningoencephalitis.
  5. Neurosyphilis.
  6. Coccidioidomycosis. (Southwestern)
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15
Q

DDx of headache in patient with HIV - Mass lesions:

A
  1. Toxoplasmosis.
  2. PML.
  3. Primary cns lymphoma.
  4. Rare pathogens/presentations - Cryptocomma, tuberculoma, Nocardia, Aspergillus, bacterial abscess.
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16
Q

Cryptococcal meningoencephalitis - Textbook presentation:

A

Patients typically have a subacute headache, malaise, and fever thta develop over days to weeks. Mental status changes may be seen.
Importantly, meningismus is often ABSENT due to the host’s inability to mount an inflammatory reaction.

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17
Q

MCC of meningoencephalitis in HIV(+):

A

Cryptococcal meningitis.

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18
Q

Transmission of cryptococcal meningoencephalitis:

A

Encapsulated fungus acquired via inhalation.

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19
Q

Cryptococcal meningoencephalitis - CD4 count:

A

<100.

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20
Q

Increased intracranial pressure in cryptococcal meningoencephalitis:

A

It is common (>20cmH2O in lateral decubitus position) - 70% of patients.

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21
Q

Cryptococcal meningoencephalitis - Mortality:

A

6-12%.

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22
Q

Pulmonary involvement in cryptococcal meningitis:

A

6-23%.

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23
Q

Cryptococcal meningitis - History:

A

65-95% - Fever.
73-100% - Headache.
Median duration of symptoms: 31 days (1-120days).

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24
Q

Cryptococcal meningitis - Physical exam:

A 
22-27% - Stiff neck.
18-22% - Photophobia.
22% - Mental status change.
10% - Focal Neurologic signs or seizures.
14% - NO CNS signs or symptoms.
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25
Q

Bottom line about clinical manifestations of cryptococcal meningitis:

A
  1. Often indolent - Small percentage exhibit meningismus or photophobia.
  2. Some patients have only fever and malaise.
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26
Q

Cryptococcal meningitis - Blood cultures positive?

A

15-35%.

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27
Q

Cryptococcal meningitis - Serum cryptococcal antigen:

A
  1. 95-100% sensitive, 96% specific.
  2. LR+ 24, LR- 0.05.
  3. Negative serum cryptococcal antigen makes diagnosis highly UNLIKELY.
  4. Serum cryptococcal antigenemia may precede clinical cryptococcal meningitis.
28
Q

In patients with positive/negative serum cryptococcal antigen results, is lumbar puncture required?

A

Yes - Regardless of serum cryptococcal antigen results.

29
Q

Routine CSF in cryptococcal meningitis is often…?

A

Normal.

30
Q

Special CSF studies for cryptococcal meningitis:

A
  1. CSF cryptococcal antigen: 91-100% sens, 93/98% specific.

2. CSF fungal culture: 95-100% sens, 100% spec.

31
Q

Poor prognosis in cryptococcal meningitis:

A
  1. Abnormal mental status.
  2. Low glycorrachia.
  3. Normal CSF cell counts.
32
Q

CMV encephalitis - Textbook presentation:

A

Typically presents in acute or subacute fashion (<8wks) with mental status changes and occasionally with focal deficits.

33
Q

CMV encephalitis - Findings include:

A
  1. Mental status changes.
  2. Drowsiness.
  3. Headache.
  4. Focal deficits.
  5. Cranial abnormalities may be seen.
34
Q

CMV encephalitis - CD4 count:

A

<50

35
Q

CMV encephalitis - Is it common in AIDS:

A

Uncommon - <2%.

36
Q

Other neurologic syndromes by CMV:

A
  1. Myelitis –> Weakness and hyperreflexia.
  2. Polyradiculopathy –> Weakness and hyporeflexia.
  3. Mononeuritis complex.
37
Q

CMV more commonly causes:

A

Gi or retinal involvement than encephalitis.

CNS involvement is usually accompanied by involvement of GI or lung.

38
Q

Prognosis of CMV encephalitis:

A

Death usually in 4-6weeks.

39
Q

CMV encephalitis - History and physical exam:

A
  1. Mental status changes common.
  2. Table 5-6 compares HIV and CMV encephalitis.
  3. Onset of CMV encephalitis is more rapid than HIV encephalitis (3.5 vs 18 weeks).
  4. Focal deficits seen in 50-70% of patients.
40
Q

Delirium - HIV vs CMV:

A

27% vs 90%.

41
Q

Apathy/withdrawal - HIV vs CMV:

A

9% vs 60%.

42
Q

Focal findings - HIV vs CMV:

A

12% vs 50-70%.

43
Q

Survival (pre HAART) - HIV vs CMV:

A

45wks vs 8.5 weeks.

44
Q

MRI in CMV encephalitis:

A 
Variety of non specific findings:
45% Periventricular enhancement.
40% atrophy and ventriculomegaly.
Rarely, ring-enhancing focal lesions.
--> Useful to rule out diseases.
45
Q

CMV encephalitis - CSF:

A
  1. Routine CSF findings not specific or sensitive.
  2. CSF culture(+) in 10-25% of patients.
  3. CSF PCR CMV.
46
Q

CSF PCR CMV:

A
  1. Test of choice for CMV encephalitis.
  2. 75% sensitive, 95% specific.
  3. LR+ 15, LR- 0.26.
47
Q

Toxoplasmosis encephalitis -Textbook presentation:

A
  1. Subacute 1-2wks although more acute presentations with confusion and seizures may be seen.
  2. Focal neurologic manifestations are common.
  3. Confusion and mental status changes may dominate the clinical picture.
48
Q

MC CNS mass lesion in AIDS patients:

A

Toxoplasmosis encephalitis.

49
Q

…% of US population seropositive for toxoplasmosis:

A

15%.

50
Q

CD4 count in toxoplasmosis encephalitis:

A

<100 in 80% of patients.

51
Q

Probability of developing toxoplasmosis encephalitis is …% in AIDS patients with CD4 <100 + Positive toxoplasmosis serology (if not receiving).

A

30%.

52
Q

Toxoplasmosis encephalitis mortality despite treatment:

A

27%.

53
Q

Toxoplasmosis encephalitis - History:

A
  1. Headache (often frontal and bilateral) - 49-73%.
  2. Seizures - 15-31%.
  3. Hallucinations - 8%.
  4. Fever - 4-68%.
54
Q

Toxo encephalitis - Physical exam:

A
  1. Focal findings (weakness, abnormal gait, or other) - 73-88%.
  2. Mental status changes - 50-67%.
  3. Mental status changes dominating clinical picture - 40%.
  4. Cognitive impairment (with normal arousal) - 66%.
  5. Stiff neck - 0%!!!
55
Q

Important point about toxo encephalitis physical exam:

A

MENINGISMUS is distinctly uncommon - IF PRESENT –> OTHER DIAGNOSIS.

56
Q

Toxo encephalitis - Lab - Serology:

A
  1. IgG - 97% sensitive.
  2. IgM - 15% sensitive, because disease is usually 2o to reactivation.
    - -> Unlikely in patients with negative IgG.
57
Q

Toxo encephalitis - CSF analysis:

A
  1. May be normal, or non specifically elevated.
  2. Percentage of patients with abnormal findings:
    50% –> WBC>5.
    81% –> Protein>40.
    14% –> Low glucose.
    33-69% –> CSF toxoplasma IgG.
58
Q

CSF PCR for toxo:

A 
Highly SPECIFIC but insensitive.
Sens 54%.
Spec 99%.
LR+ 54.
LR- 0.46.
59
Q

Toxo encephalitis - Neuroimaging - Test of choice:

A

MRI.

60
Q

MRI findings in toxo encephalitis:

A
  1. Superior to contrast CT and affects course in 40% of patients.
  2. Demonstrates 1 or more ring enhancing lesions with mass effect and edema.
  3. Lesions may be located in basal ganglia, thalamus, and cortex.
  4. Single lesion in 14% of patients.
  5. Single lesions make toxo encephalitis less likely and increase likelihood of CNS lymphoma.
61
Q

CT in toxo encephalitis:

A
  1. Single ring-enhancing lesion - 35%.
  2. > 2 ring enhancing lesions - 62%.
  3. Hypodense lesions - 13%.
  4. Moderate to severe cerebral edema - 48%.
  5. 75% of lesions located in cerebral hemispheres.
62
Q

In patients with normal contrast CT scan or a single enhancing lesion?

A

MRI is recommended.

63
Q

Brain biopsy is associated with …% mortality and …% morbidity:

A

0.5-3.1% mortality, 10-40% morbidity.

64
Q

Empiric treatment for toxoplasmosis encephalitis is normally instituted in patients who fulfill ALL of the following criteria:

A
  1. Multiple mass lesions.
  2. CD4 <100.
  3. Positive toxo serology.
  4. Are NOT already receiving toxo prophylaxis.
65
Q

Steroids in therapy of toxo encephalitis:

A

Indicated for patients with cerebral edema + midline shift, or clinical deterioration within first 48hr of therapy.

66
Q

Prevalence of AIDS (December 2007):

A

About 33.2 million people reportedly living with HIV worldwide.

Project - USMLE Step 3 (82 decks)

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