Human Immunodeficiency Virus

Question 1

Definition

Answer 1

Infection with the human immunodeficiency virus (HIV)

Question 2

Aetiology/Transmission

Answer 2

• HIV is transmitted by:

o Sexual intercourse
• Heterosexual intercourse is the MOST COMMON mode of transmission
• Homosexuals are at greater risk in the West

o Blood (and other bodily fluids)
• Mother to child (intrauterine, childbirth, breastfeeding)
• Needles
• Blood transfusions
• Organ transplantation

Question 3

Pathophysiology

Answer 3

o HIV enters CD4+ lymphocytes by binding to their gp120 receptors
o Reverse transcriptase allows the incorporation of HIV genetic material into the host genome
o This leads to dissemination of HIV, cell death and eventual T-cell depletion

Question 4

Epidemiology

Answer 4

Increasing in incidence in Africa and Asia

Question 5

Presenting symptoms/Signs on physical examination (stage 1)

Answer 5

There are THREE phases of HIV:
Seroconversion
Early/Asymptomatic
AIDS

o Seroconversion
• Self-limiting
• Fever
• Night sweats
• Generalised lymphadenopathy
• Sore throat
• Others: oral ulcers, rash, myalgia, headache, encephalitis, diarrhoea

Question 6

Presenting symptoms/Signs on physical examination (stage 2)

Answer 6

o Early/Asymptomatic

• Apparently well
• Some may have persistent lymphadenopathy
• Progressive minor symptoms (e.g. rash, oral thrush, weight loss)

Question 7

Presenting symptoms/Signs on physical examination (stage 3)

Answer 7

AIDS

• Syndrome of secondary diseases resulting from immunodeficiency

Question 8

Presenting symptoms/Signs on physical examination (direct effects)

Answer 8

Direct Effects of HIV Infection

o Neurological: polyneuropathy, dementia
o Lung: lymphocytic interstitial pneumonitis
o Heart: cardiomyopathy, myocarditis
o Haematological: anaemia, thrombocytopaenia
o GI: anorexia, wasting
o Eyes: cotton wool spots

Question 9

Presenting symptoms/Signs on physical examination (secondary effects)

Answer 9

Secondary effects resulting from immunodeficiency

o Bacterial Infection: TB, skin infections, pneumococcal infections
o Viral: CMV, HSV, VZV, HPV, EBV
o Fungal: pneumocystic jirovecii pneumonia, Cryptococcus, candidiasis, invasive aspergillosis
o Protozoal: toxoplasmosis, cryptosporidia
o Tumours: Kaposi sarcoma, SCC, non Hogkin’s lymphoma, Hodgkin’s lymphoma

Question 10

Investigations

Answer 10

• HIV testing - HIV antibodies, PCR for viral RNA, CD4 count, viral load

• Others
o Pneumocystic pneumonia - CXR
o Cryptococcal meningitis - brain CT or MRI, LP
o CMV (colitis) - colonoscopy and biopsy
o Toxoplasmosis - brain CT or MRI
o Cryptosporidia - stool microscopy