Question
A 35-year-old male with history of multiple sex partners was admitted with complaints of unexplained fever, progressive loss of weight, persistent diarrhea and generalized lymphadenopathy for past six months What is the most probable diagnosis Draw a labeled diagram of the morphology of the causative agent of this condition Discuss the pathogenesis Write lab diagnosis of the above condition in detail Name two parasites causing diarrhoea in this group of patients Mention the prophylactic measures (1+1+2+3+1+2)
Answer
Most probable diagnosis: AIDS (HIV infection) — history of multiple sex partners, unexplained fever, progressive weight loss, persistent diarrhoea, and generalized lymphadenopathy for six months is classical of advanced HIV disease.
Morphology of HIV (described, since a labelled diagram cannot be rendered in this text-based answer — the description below covers the key labelled features): HIV is a spherical, enveloped retrovirus, ~100–120 nm in diameter. The outer lipid envelope is studded with glycoprotein spikes — gp120 (outer, CD4-receptor binding) and gp41 (transmembrane, mediates membrane fusion). Beneath the envelope lies the matrix protein (p17). The conical capsid (core), formed by p24 protein, encloses two copies of single-stranded RNA genome, along with the viral enzymes reverse transcriptase, integrase, and protease.
Pathogenesis: HIV infects cells bearing the CD4 receptor (with a chemokine co-receptor, CCR5 or CXCR4) — chiefly CD4+ T-helper lymphocytes, macrophages, dendritic cells. Reverse transcriptase converts viral RNA to DNA, which integrates into the host genome (via integrase); progressive destruction of infected CD4+ cells over months to years causes a progressive decline in CD4+ T-cell count, crippling cell-mediated immunity, and once counts fall below critical thresholds, opportunistic infections/malignancies (AIDS) develop.
Laboratory diagnosis
- Screening: ELISA (4th-generation combination assays detect both p24 antigen and antibody).
- Rapid tests: point-of-care immunochromatographic rapid antibody tests.
- Confirmatory test: Western blot or supplemental testing algorithm per NACO Strategy III (three different tests/kits).
- CD4 count: flow cytometry, for staging/prophylaxis decisions.
- Viral load: quantitative HIV RNA PCR, for monitoring treatment response.
Two parasites causing diarrhoea in this group: Cryptosporidium parvum and Isospora (Cystoisospora) belli (Microsporidia is another valid example).
Prophylactic measures: safe sexual practices (condom use, partner reduction); screening of blood/blood products; safe injection practices; prevention of mother-to-child transmission; post-exposure prophylaxis after high-risk exposure; pre-exposure prophylaxis (PrEP) for high-risk individuals; health education.