HIV Flashcards
definition of HIV
infection with HIV - retrovirus which replicates in human lymphocytes (CD4+ and macrophages)
HIV1 - global epidemic
HIV2 - less pathogenic, predominantly west Africa
= progressive immune system dysfunction, opportunistic infection, and malignancy
= AIDS
aetiology of HIV
transmitted by:
- sexual intercourse - heterosexual is most common world wide, but increased risk in homosexuals in west
- blood and other bodily fluids
- mother to child (intrauterine, childbirth, breastfeeding)
- needles - drug users, healthcare workers
- blood product transfusion
- organ transplantation
pathology of HIV
enters the CD4 lymphocytes following following binding of its envelope glycoprotein (gp120) to CD4 (on T cells, monocytes and macrophages) and a chemokine receptor
CD4 cells migrate to lymphoid tissue where the virus replicates
reverse transcriptase (in viral core) reads RNA to manufacture DNA, which is incorporated into the host genome - error prone = high mutation rate = treatment resistance
dissemination of virions leads to cell death and eventually T cell depletion, and infection of more CD4 cells
= reduced immune func of CD4 cells
epidemiology of HIV
on the rise in Africa and Asia
Africa has most of disease and mortality
>40million adults affected ww
1.2million deaths/yr
UK 100000 living with HIV
sx of HIV - 3 phases
- seroconversion
- 4-8wk post-infection
- self-limiting - fever, night sweats, generalised lympadenopathy, sore throat, oral ulcer, erythematous/maculopapular rash, myalgia, headache/aseptic meningitis, encephalitis, diarrhoea
- early/asymptomatic
- 18mo-15+ yrs
- apparently well - some may have persistent lymphademopathy (>1cm nodes, at 2+ extrainguinal sites for >3mo) due to follicular hyperplasia
- progressive minor symproms - rash, oral thrush, weight loss, malaise
- AIDS
- syndrome of secondary disease reflecting severe immunodeficiency or diect effect of HIV infection
- CD4 count <200/mm3
direct effects of HIV infection
neuro - polyneuropathy, myelopathy, dementia
lung - lymphocytic interstitial pneumonitis
heart - cardiomyopathy, myocarditis
haematological - anaemia, thrombocytopenia
GI - anorexia, HIV enteropathy (malabsorption and diarrhoea), severe wasting
eyes - cotton wool spots
secondary bacterial infections arising from immunodeficiency
mycobacteria (lungs, GI, skin) eg mycobacterium tuberculosis, mycobacterium avium intracellular (late),
staphylococci (skin),
salmonella,
capsulated organism (streptococcus pneumoniae, haemophilus influenzae)
secondary viral infections arising from immunodeficieny
CMV - rhinitis, oesophagitis, colitis, pneumonitis, adrenalitis, encephalitis
HSV - encephalitis
VZV - recurrent shingles
HPV - warts
papovavirus - progressive multifocal leucoencephalopathy with motor, interlectual and speech impairment
EBV - oral hairy leukoplakia on the side of the tongue
secondary fungal infections arising from immunodeficiency
pneumocystis pneumonia (PCP
cryptococcus (meningitis)
candida (opral, airway, genital, oesophageal)
invasive aspergillosis
secondary protazoal infections arising from immunodeficiency
toxoplasmosis - cerebral abscess, chorioretinitis, encephalitis
cryptosporidia and microsporidia - diarrhoea
tumours in HIV pts
kaposi sarcoma - cutaeneous or conjunctival vascular tumour caused by human herpesvirus (HHV8)
squamous cell carcinoma - particularly cervical or anal
non-hodgkin’s B cell lymphoma (brain, GI)
hodgkin’s lymphoma
investigations for HIV
HIV testing after discussion and consent - HIV Ab usually +ve by 12wk after exposure, PCR for viral RNA or incorporated proviral DNA. Monitor CD4 count and viral load
for pneumocystic pneumonia (PCP) - CXR bilateral perihilar/ground glass shadowing, bronchoalveolar lavage
cryptococcal meningitis - brain CT or MRI, LP - CSF microscopy (india ink staining), culture, ELISA for ag
CMV (colitis) - colonoscopy and biopsy - cytomegalic cells with inclusions
toxoplasmosis - brain CT or MRI shows ring enhancing lesions
cryptosporidia/microsporidia - stool microscopy
Prevention of HIV
sexual transmission - consistent and correct use of condoms, serosorting is restriction of unsafe sex depending on HIV status - unsafe because tests are inaccurate, treatment resistence, other STIs and hepatitis
post-exposure prophylaxis - short-term course of ART is emergency therapy, up to 72hr after, ideally <24 - not if exposure from undetectable person
pre-exposure prophylaxis - ART in high risk groups
vertical transmission - all pregnant women with HIV should have started ART by 24weeks gestation, c section of viral load >50copies/mL. Neonatal PEP from birth-4wks
RF for HIV
serodifferent relationships w/o suppression of viral load
condomless anal sex in MSM
when do you test for HIV
dx of primary HIV - Ab may be -ve but RNA high
testing in sexual health clinics, antenatal services, drug dependancy programmes, in pts with TB, hep B, hep C, lymphoma
HIV testing
ELISA for HIV Ab and Ag - 4th generation assays test for HIV Ab and p24 Ag - reduces window period of false negative testing. Dx confirmed by confirmatory assay
rapid point of care testing - immunoassay kit = rapid result from finger-prick/mouth swab
viral load - quantification of HIV RNA - monitor response to ART - not dx because false +ve
nucleic acid testing/viral PCR - qualitative test for presence of viral RNA - test for vertical transmission
CD4 count - not dx, monitro immune system function and disease progression
dx criteria for AIDS
<200 cells/microlitre (one of the criteria)
pneumocystis jirovecii
opportunistic infection from HIV
progressive SOB on exertion, malaise, dry cough, haemoptysis, pleuritic chest pain
increased RR
SpO2 (compare rest and exertion),
CXR - perihilar infiltrates/normal
induced sputum or BAL with staining or nucleic acid amplification
candidiasis - opportunistic from HIV
oral or oesophageeal
pain in tongue, dysphagia, odynophagia
dx clinically/endoscopically
cryptococcus neoformans
commonest systemic fungal infection in HIV
meningitis: headache, fever, meningism
skin molluscum like papules and lung disease
LP with manometry
CSF stain (India ink)
CSF/blood cryptococcal ag
toxoplasma gondii
opportunistic from HIV
commonest cause of intracranial mass lesions when CD4<200cells/microlitre
focal neurological signs and seizures
headache and vomiting if raised ICP
ring enhancing lesions on MRI with associated oedema
CSF PCR for T. gondii
cytomegalovirus
opportunistic infection with HIV
severe primary or reactivated disease
retinitis - blurred then loss of vision
encephalitis
GI disease - oesophagitis, colitis
hepatitis
bone marrow suppression
pneumonia
serum CMV viral load, retinal lesions, GI ulceration, owl’s eye inclusions on biospy
cryptosporidium
chronic cause of chronic diarrhoea in HIV pre-ART
acute or subacute non-bloody, watery diarrhoea
cholangitis
pancreatitis
stool microscopy - multiple samples as oocyst excretion intermittent
PCR
enzyme immunoassay
direct flurescent Ab
Kaposi’s sarcoma
most common tumour in HIV and AIDs defining
caused by kaposi sarcoma herpes virus - HHV8
cutaneous/mucosal lesions - patch, plaque, or nodular
visceral disease less common
histological confirmation
lymphoma with HIV
increased risk of non-Hodgkin’s lymphoma in HIV
diffuse large cell B lymphoma, Burkitt’s lymphoma, primary CNS lymphoma
sx depend on area of involvement
lymphadenopathy, cytopenia, CNS sx
