HIV Flashcards
HIV pathophysiology
causes immunosuppression by:
disrupting CD4+ T cell function (cytotoxic proteins, apoptosis)
consequent failure of both humoral and cell mediated immune responses
impaired thymopoesis (new T cell production)
direct cytopathic effects on other cells ( e.g. glial cells in the CNS)
gut microbial translocation and chronic inflammation
latent period between seroconversion and HIV deisease
mean is 10 years
25% disease free at 10 years
some may progress more rapidly
baseline viral load is a predictor of progression
seroconversion
the period of time during which HIV antibodies develop and become detectable. usually takes place within a few weeks following infection. often, but not always, accompanied by a flu like illness, rashes, arthalgia and lymphadenopathy
opportunistic infections at different CD4 counts
> 200 - TB, oro-pharyngeal candidiasis, herpes zoster, pneumococcal and other pneumonias
100-200 - pneumocystis pneumonia, histoplasmosis, progressive multifocal leukoencephalopathy (PML)
<100 - atypical mycobacterial disease/miliary or extrapulmonary TB, CMV retinitis/colitis toxoplasmosis, cryptococcosis
AIDS defining events
major opportunist infections - pneumocystis pneumonia, toxoplasmosis, multidermatomal shingles, cryptococcosis
opportunist neoplasms - karposi’s, lymphoma, cervical carcinoma
recurrent bacterial pneumonias
severe weight loss (>10% of presumed or measured body weight)
HIV testing
4th gen usually consist of 3 immunoassays & p24 antigen to detect early infection
wait until a 2nd, confirmatory blood test shows HIV before giving result to the patient
usual to test for syphilis and hep B & C at the same time, given the relatively high incidence in the group of patients being tested
Karposi’s sarcoma
induced by HHV8
highly active anti-retroviral therapy (HAART) often sufficient
loca radiotherapy
cytotoxic drugs (vinblastine, bleomycin, adriamycin)
HIV ass. lymphomas
most common is high grade B cell NHL
other types occur e.g. primary CNS
radio/chemo HAART
outcomes generally as good as lymphomas in non HIV infected, so long as taking HAART
bacterial pneumonia
commoner in HIV, esp pneumococcus (& staphylococcus)
may be recurrent
impaired response to polysaccharide antigens and altered IgG subtypes may contribute
pneumocystis jiroveci (carnii) pneumonia
usually occurs when CD4 <250
was the AIDS defining illness in 66% of cases early in the epidemic
often a sub-acute presentation with dry cough, sweats and increasing SOB
chest signs often minimal
pneumocystis pneumonia diagnosis
CXR
exercise induced oxygen desaturation
antibody fluorescent staining of cysts or PCR of bronchoalveolar lavage fluid (best) or induced sputum
treat on suspicion whilst awaiting results
pneumocystis treatment
ventilatory support if severe hypoxia
high dose cotrimoxazole for 3/52
steroids if resp impairment
monitor for cotrimoxazole side effects (allergic and haematological)
TB
very strong ass. w/ HIV in the developing world - up to 65%
increased smear negative infections which may impair diagnosis
requires scrupulous attention to control of infection and adherence issues: also important issues with ART and TB drug interactions and overlapping toxicities
generally best to complete intensive phase of TB therapy first then start ART (unless CD4 <100)
CMV disease in HIV
occurs in advanced immunodeficiency, CD4< 50
multi-organs susceptible, e.g. lung, GI tract
eye the commonest site of localised CMV infection
Tx: IV ganciclovir/oral valganciclovir
CNS disease in AIDS
opportunist infections: cryptococcal or TB meningitis, CMV or toxoplasmosis encephalitis primary cerebral lymphoma HIV dementia complex spinal cord disease peripheral and autonomic neuropathy
