Human Immunodeficiency Virus (HIV)

Question 1

Pathophysiology of HIV

Answer 1

• HIV enters CD4 lymphocytes following binding of its envelope glycoprotein (gp120) to CD4 and a chemokine receptor
• Reverse transcriptase reads RNA to manufacture DNA
• Viral DNA is incorporated into host genome
• Dissemination of virions leads to cell death
• Prolonged cell death leads to T-cell depletion

Question 2

Type of virus HIV

Answer 2

Retrovirus

Question 3

Routes of HIV transmission

Answer 3

Sexual contact
Pregnancy, childbirth, breast-feeding
IV drug use
Occupational exposure
Blood transfusion/organ transplant

Question 4

Four stages of untreated HIV infection

Answer 4

Flu-like (4-8 weeks post-infection)
Feeling fine (18 months-15 years)
Falling count (CD4 count dropping)
Final crisis (CD4 <200)

Question 5

Presentation of HIV

Answer 5

Usually depends on opportunistic infectious organism

Question 6

Bacterial HIV opportunistic infectious agents

Answer 6

Mycobacteria (lungs, GI, skin)
Staph
Salmonella
Strep pneumoniae
Haemophilus influenzae

Question 7

Viral HIV opportunistic infectious agents

Answer 7

CMV (cytomegalovirus)
HSV (encephalitis)
VZV (shingles)
HPV (warts)
Papovavirus (progressive multifocal leukoencephalopathy)
EBV (oral hairy leukoplakia)

Question 8

Fungal HIV opportunistic infectious agents

Answer 8

Pneumocystis pneumonia
Cryptococcus (meningitis)
Candida
Invasive aspergillosis

Question 9

Protozoal HIV opportunistic infectious agents

Answer 9

Toxoplasmosis
Cryptosporidia
Microsporidia (diarrhoea)

Question 10

Potential CXR findings in opportunistic infection in HIV+ve patient

Answer 10

Severe bilateral pulmonary interstitial infiltrates with pneumatoceles

Question 11

Irregular, white, painless plaques on lateral tongue that cannot be scraped off

Answer 11

Hairy leukoplakia - caused by EBV in HIV+ve or organ transplant recipients (immunosuppressed)

Question 12

Contrasting features between hairy leukoplakia, thrush, and leukoplakia

Answer 12

Thrush - scrapable
Leukoplakia - precancerous
Hairy leukoplakia - non-scrapable and present in the immunosuppressed

Question 13

Conditions and associated risk factors; forms of candidiasis

Answer 13

Oral candidiasis, oesophageal thrush (immunocompromise)

Vulvovaginitis (diabetes, use of ABx)

Diaper rash

Infective endocarditis (IV drug users)

Disseminated candidiasis (neutropenic patients = endogenous immunocompromise)

Question 14

Signs/symptoms of forms of candidiasis

Answer 14

Oral/oesophageal - dysphagia

Vulvovaginitis/balanitis - thick discharge, itching, soreness, redness

Diaper rash

Endocarditis

Disseminated candidiasis - fever, hypotension +/- leukocytosis

Question 15

Investigations in suspected candidiasis

Answer 15

Swabs are not routinely recommended as candidal organisms commonly found in healthy individuals

Other Ix to exclude differentials/risk factors

• urinalysis (UTI)
• random/fasting glucose
• OGTT
• HIV antibody test
• vaginal pH test (STIs)

Question 16

Dissemination sites in disseminated candidiasis

Answer 16

Retina
CNS
Kidney Liver Spleen
Bones

Question 17

HIV-associated tumours

Answer 17

Kaposi’s sarcoma
Squamous cell carcinoma (cervical/anal - HPV)
Lymphoma

Question 18

Pink/purple patch on skin/mouth caused by HHV8

Answer 18

Kaposi’s sarcoma

- AIDS-defining condition

Question 19

Investigations in HIV

Answer 19

• ELISA confirmed with Western blot (first line when HIV testing indicated, confirm positive with Western blot/second ELISA)
• Serum HIV rapid test (point of care test)
• Serum HIV DNA PCR (infants)
• CD4 count (immune status + staging)
• Serum viral load (HIV RNA) (>1000 copies/mL is diagnostic, can be falsely positive tho)

Question 20

CD4 count HIV stages (cells/mL)

Answer 20

> 500 - usually asymptomatic

<350 - implies substantial immune suppression

<200 - AIDS + high risk of opportunistic infections