AKT · Infections/HIV & opportunistic infection

HIV & opportunistic infection

Human immunodeficiency virus — retrovirus depleting CD4 T-cells → opportunistic infection/malignancy

Overview

A retrovirus that progressively destroys CD4 T-lymphocytes, causing immunodeficiency. It is the hub of the immunocompromised host: the CD4 count predicts which opportunistic infections and malignancies occur. Presentations range from a seroconversion illness, through an asymptomatic latent phase, to AIDS-defining opportunistic disease. Antiretroviral therapy (ART) is for everyone, restores immunity, and renders the virus untransmittable when suppressed (U=U). (Transmission/PrEP/PEP detail is on sexual_health.)

Recognise

Seroconversion: a glandular-fever-like illness (fever, rash, lymphadenopathy, pharyngitis, mouth ulcers) 2–6 weeks after exposure — a key 'don't-miss' (test for HIV)
AIDS-defining/opportunistic disease by CD4: <200 → Pneumocystis jirovecii pneumonia (PCP — exertional desaturation, dry cough), cerebral toxoplasmosis (ring-enhancing lesions), oesophageal candidiasis; <100 → cryptococcal meningitis, CMV retinitis, primary CNS lymphoma; <50 → MAC, CMV; any CD4 → TB
Also: Kaposi sarcoma (HHV-8), seborrhoeic dermatitis, oral hairy leukoplakia, recurrent shingles/zoster, weight loss

Red flags

AIDS-defining illness (PCP, cryptococcal meningitis, cerebral toxoplasmosis, CMV retinitis) → urgent specialist treatment + ART
Acute seroconversion or any at-risk presentation → TEST for HIV (it is missed when not considered); immune reconstitution inflammatory syndrome (IRIS) after starting ART

Differentials & how to tell them apart

Other causes of immunosuppressionchemo, steroids, primary immunodeficiency — but test for HIV in any unexplained opportunistic infection

Seroconversion vs EBV/CMV mononucleosisoverlapping — HIV test (and consider in any glandular-fever-like illness with risk)

AIDS-defining infection differentialsPCP vs bacterial pneumonia; toxoplasmosis vs CNS lymphoma (both ring-enhancing — toxo usually multiple, responds to a treatment trial)

Kaposi sarcoma — violaceous plaques (HHV-8, AIDS-defining)
M. Sand et al. / CC BY 2.0 — Wikimedia Commons

Investigations

HIV antigen/antibody test (4th-generation) ± confirmatory; CD4 count and HIV viral load (stage/monitor); screen for co-infections (TB, hepatitis B/C, STIs); opportunistic-infection work-up directed by CD4 and presentation (CXR/induced sputum for PCP, CT/LP for CNS, fundoscopy for CMV).

Management

ART for everyone (2 NRTIs + INSTI) + treat/prophylaxis of opportunistic infection by CD4

1TEST for HIV in any seroconversion illness, opportunistic infection or at-risk presentation (it's missed when not considered). Stage with CD4 count and viral load; the CD4 predicts the opportunistic infections.Gate: AIDS-defining illness by CD4 → urgent treatment: PCP (CD4 <200) → co-trimoxazole + steroids if hypoxic; cerebral toxoplasmosis → pyrimethamine-sulfadiazine; cryptococcal meningitis (CD4 <100) → amphotericin + flucytoside. Start co-trimoxazole PROPHYLAXIS once CD4 <200.
2Start ART for everyone (restores immunity, U=U), screen/treat co-infections (TB, hepatitis), vaccinate, and watch for IRIS after ART initiation. Transmission/PrEP/PEP detail on sexual_health.

Antiretroviral therapy (ART) for EVERYONE — usually 2 NRTIs + a third agent (INSTI) — start regardless of CD4; restores immunity; suppressed virus = Untransmittable (U=U); lifelong adherence

Treat the opportunistic infection + prophylaxis by CD4 — PCP → co-trimoxazole (+ steroids if hypoxic); CD4 <200 → co-trimoxazole PROPHYLAXIS; toxoplasmosis → pyrimethamine-sulfadiazine; cryptococcal meningitis → amphotericin + flucytoside

Screen/treat co-infections; vaccinate — TB, hepatitis B/C, STIs; avoid live vaccines if very immunosuppressed

Watch for IRIS after starting ART — paradoxical worsening as immunity recovers; specialist HIV care

Key points

HIV depletes CD4 → the CD4 count predicts the opportunistic infection: <200 PCP/toxoplasmosis/oesophageal candida; <100 cryptococcal meningitis/CMV retinitis/CNS lymphoma; <50 MAC. ART for EVERYONE (U=U). Co-trimoxazole prophylaxis at CD4 <200. TEST for HIV in any seroconversion/opportunistic illness — it's missed when not considered. Watch for IRIS after starting ART.

Monitor & prognosis

CD4/viral load, ART adherence/toxicity, opportunistic-infection prophylaxis, co-infection screening, IRIS.

With ART, near-normal life expectancy and untransmittable; untreated → progressive immunodeficiency and AIDS-defining disease.

Source: BHIVA; NICE; cross-ref sexual_health (transmission/PrEP/PEP), respiratory (PCP/TB), neurology (CNS infections)