IM6.1-6 | HIV Foundations and Opportunistic Disease — Summary & Reflection

KEY TAKEAWAYS

HIV is an RNA retrovirus (HIV-1 and HIV-2) that depletes CD4+ T lymphocytes, causing progressive combined immunodeficiency. Acute HIV seroconversion (2–4 weeks post-exposure) mimics infectious mononucleosis — fever, pharyngitis, generalised lymphadenopathy, maculopapular rash (involving palms), oral ulcers — and occurs during high viraemia before antibodies appear. The CDC classification defines AIDS as CD4 <200 cells/µL OR any Category C AIDS-defining condition. WHO stages 1–4 allow clinical staging without CD4 testing; Stage 4 includes PCP, cerebral toxoplasmosis, cryptococcal meningitis, HIV wasting, KS, and extrapulmonary TB.

CD4 thresholds guide OI risk: <200 — PCP (prophylaxis: co-trimoxazole), Toxoplasma (if IgG+); <100 — Cryptococcal meningitis (CrAg screening + fluconazole pre-emptive); <50 — Disseminated MAC, CMV retinitis.

Key OIs: PCP (bilateral ground-glass CXR, high LDH, treat with high-dose TMP-SMX + corticosteroids if severe); Cerebral toxoplasmosis (multiple ring-enhancing lesions in basal ganglia, treat empirically with pyrimethamine + sulfadiazine); Cryptococcal meningitis (subacute headache, elevated ICP, India ink positive, treat with Amphotericin B + flucytosine + therapeutic LP).

AIDS-defining malignancies: Kaposi sarcoma (HHV-8, violaceous skin/mucosal nodules, ART ± chemotherapy); NHL including PCNSL (EBV-linked, ring-enhancing single lesion in basal ganglia); Invasive cervical cancer (HPV-driven, screen PLHIV women more frequently).

HIV skin/oral markers: Oral candidiasis (white scrape-able plaques, CD4 <300); oral hairy leucoplakia (white lateral tongue streaks, NON-scrape-able, EBV, WHO Stage 2); seborrhoeic dermatitis (Stage 2); herpes zoster (young adult, Stage 2); pruritic papular eruption (Stage 3–4); Kaposi sarcoma (dark violaceous nodules, HHV-8).

REFLECT

Consider Rajan from the opening hook — his mononucleosis-like illness went undiagnosed for five years before today's presentation. In that time, his CD4 count has been silently falling, and he has been potentially transmitting HIV to partners, unaware of his status. Reflect on two questions: First, what clinical clue in his original presentation five years ago should have prompted an HIV test? Second, consider the woman with PCP — she had no prior HIV diagnosis. At what CD4 level does PCP typically occur, and what does this mean for how early we must test and start ART? Now think about a real patient encounter you may have in a district hospital in India: a 25-year-old with white tongue lesions, seborrhoeic dermatitis, and unexplained weight loss — how would you stage this patient clinically before any blood test, and what is the most important single investigation to request? These reflective questions encode the clinical reasoning that transforms factual knowledge into practical competence.