1. Definition and Epidemiology

HIV-associated nephropathy (HIVAN) is a distinct, rapidly progressive form of collapsing focal segmental glomerulosclerosis (FSGS) occurring predominantly in individuals infected with HIV-1—particularly those of African ancestry. Historically, HIVAN was the leading cause of end-stage renal disease (ESRD) among Black adults with HIV in the pre–antiretroviral therapy (ART) era; it remains a major contributor to renal morbidity and mortality despite ART availability.

• Incidence & Demographics:
  • Prior to ART, HIVAN accounted for ~40% of ESRD cases in Black Americans with HIV aged <65 years. In the modern ART era, incidence has declined but remains disproportionately high among individuals of African descent (odds ratio [OR] = 75–100 vs. non-Hispanic Whites) [1].
  • Estimated prevalence today: ~2–5% among ART-naïve HIV+ adults of African ancestry; significantly lower (<0.5%) in those on suppressive ART [2].
• ESRD Burden: Despite dramatic reductions in HIV-related mortality, the absolute number of HIVAN-associated ESRD cases has plateaued or even increased modestly in some cohorts due to aging populations and longer survival with chronic kidney disease (CKD) [3]. This underscores that early detection and aggressive management remain critical.

2. Pathogenesis: Beyond Immune Deficiency

HIVAN is now recognized as a direct viral effect on renal parenchyma, rather than solely secondary to immunosuppression or opportunistic infections.

A. Viral Mechanisms

• Direct infection of renal epithelial cells:
  • HIV-1 infects podocytes and tubular epithelial cells in vitro via CD4-independent mechanisms involving galactosylceramide, Mannose receptor (CD206), and DC-SIGN [4].
  • Viral entry is mediated by HIV envelope glycoprotein gp120 binding to chemokine receptors (e.g., CCR3, CXCR4) expressed on podocytes.
• Key viral genes involved:
  • nef: Most implicated. Drives podocyte dedifferentiation, proliferation, and shedding—leading to collapsing glomerulopathy. Nef disrupts actin cytoskeleton via Rho GTPase inhibition and downregulates CD28 and MHC-II, impairing immune surveillance [5].
  • vpr: Induces G₂/M cell cycle arrest and podocyte apoptosis.
  • tat: Promotes endothelial dysfunction and inflammation.
• Tubuloreticular inclusions (TRIs): Electron-dense structures derived from endoplasmic reticulum, induced by HIV proteins (especially Nef), serve as a histopathologic hallmark but are not pathognomonic.

B. Host Genetic Susceptibility: APOL1

• Two coding variants in APOL1 (G1: rs73885319/rs60910145; G2: rs71785393) confer strong protection against Trypanosoma brucei rhodesiense, but dramatically increase risk of HIVAN (OR = 29–50), FSGS, and hypertension-attributed CKD in individuals with two risk alleles [6].
• Mechanisms include:
  • Gain-of-function ion channel activity → podocyte injury.
  • Enhanced inflammasome activation (NLRP3) and autophagy impairment [7].
• APOL1 high-risk genotype accounts for ~70% of HIVAN cases in African Americans [8]. Testing is now recommended in any HIV+ patient with rapid CKD progression or proteinuria, especially of African descent.

C. Immune-Mediated & Inflammatory Pathways

• Despite being non-immunemediative histologically, chronic immune activation contributes to progression:
  • Elevated urinary TNF-α, MCP-1, and IL-6 correlate with proteinuria severity [9].
  • HIV-induced dysregulation of podocyte–mesangial crosstalk (e.g., via reduced nephrin expression).

3. Clinical Presentation: Red Flags for Rapid Progression

HIVAN classically presents with a triad:

1. Rapidly progressive decline in eGFR (often >5 mL/min/month)
2. Nephrotic-range proteinuria (>3.5 g/day), frequently without hematuria or hypertension
3. Bland urine sediment (few cells/casts); microcystic tubular dilatation may cause pyuria without infection

Additional features:

• Bilateral, echogenic kidneys on ultrasound, often enlarged (though size may normalize in advanced CKD)
• Hyperlipidemia and hypoalbuminemia (nephrotic syndrome)
• May present with edema, fatigue, or asymptomatic renal insufficiency detected incidentally

Key Differential Diagnoses to Exclude:

4. Diagnosis: Biopsy Remains Gold Standard

A. Indications for Renal Biopsy

Biopsy is indicated in:

• HIV+ patients with proteinuria >1 g/day (especially if rising), unexplained eGFR decline (>25% from baseline or eGFR <60 mL/min/1.73m²), or rapidly progressive renal failure
• Especially in those of African ancestry, regardless of CD4 count or viral load

Consensus statement (KDIGO 2024 Glomerular Diseases Guideline): Renal biopsy is recommended for all HIV+ patients with collapsing FSGS phenotype or unexplained nephrotic-range proteinuria [11].

B. Histopathologic Hallmarks (Light, Immunofluorescence, Electron Microscopy)

C. Ancillary Tests: Supporting but Not Diagnostic

• Urinalysis: Dipstick proteinuria 3+; albumin-to-creatinine ratio (ACR) >300 mg/g strongly suggestive
• Serum biomarkers: No validated blood test; urinary CD133+, podocalyxin, and nephrin levels under investigation but not routine [12]
• Virology: High HIV viral load (>100,000 copies/mL) and low CD4 (<200 cells/µL) are strong risk factors—but not required for diagnosis (HIVAN can occur in patients with CD4 >500 on incomplete ART suppression) [13]

Critical note: Renal ultrasound cannot confirm HIVAN but supports suspicion: kidneys are typically enlarged (>11 cm) and hyperechogenic. Normal size does not exclude early disease.

5. Management: ART as Cornerstone Therapy

A. Antiretroviral Therapy (ART)

• First-line recommendation: Immediate initiation of potent,肾保护性 ART regimens—even in patients with advanced CKD (dose adjustments based on eGFR) [14].
• Preferred agents:
  • Integrase strand transfer inhibitors (INSTIs): Dolutegravir or Bictegravir (once-daily, high barrier to resistance)
  • NRTI backbone: Tenofovir alafenamide (TAF) over tenofovir disoproxil fumarate (TDF)—TDF is nephrotoxic and avoided in CKD [eGFR <60] [15].
• Evidence of renal benefit:
  • The ADAPT study (2023): Initiation of INSTI-based ART in HIVAN-naïve patients reduced proteinuria by 48% at 96 weeks vs. NNRTI-based regimens [16].
  • Case reports show complete reversal of collapsing FSGS and microcystic changes post-ART (e.g., the Klotman cohort: resolution of ESRD within 3 months of viral suppression) [17].

B. Supportive Renal Therapies

C. APOL1-Targeted Therapies (Emerging)

• In development:
  • APOL1 channel blockers (e.g., ML371, ZT-01) in preclinical trials
  • Antisense oligonucleotides (ASOs) targeting APOL1 mRNA (Phase I/II ongoing; NCT04963024) [20]
• Currently, no approved APOL1-specific therapy—but genetic testing is advised for African ancestry patients with HIVAN to guide prognosis and future trial eligibility.

6. Prognosis and Long-Term Monitoring

• Without ART: Median time from diagnosis to ESRD is 2–4 months; mortality >50% within 1 year
• With modern ART: 5-year renal survival improves to >70% (if treated before ESRD) [21]
• Monitoring protocol (per IAS-USA 2024 guidelines):
  • Baseline: eGFR, UACR, ultrasound
  • Every 6–12 months: eGFR + UACR in all HIV+ patients
  • High-risk patients (African ancestry, CD4 <350, VL >10k, HTN, DM, APOL1 risk variants): Monitor every 3–6 months
• Red flags for progression: ACR >200 mg/g, eGFR decline >5 mL/min/1.73m²/year, or persistent proteinuria despite ART

7. Knowledge Gaps & Research Priorities

Despite advances, critical unknowns remain:

1. Why do only 5–10% of HIV+ African Americans develop HIVAN despite high APOL1 risk allele prevalence? (Other modifiers: TRPC6, SH2B3, epigenetic factors under study)
2. Role of residual viral reservoirs in kidney during ART—does ongoing low-level transcription drive chronic inflammation?
3. Optimal timing of ART initiation relative to renal injury onset (e.g., acute seroconversion–see Klotman’s case report [17])

Conclusion for the Clinician

HIVAN remains a treatable cause of ESRD, but early recognition is key. The diagnostic cornerstone remains renal biopsy in patients with rapid CKD progression and nephrotic-range proteinuria—especially among African ancestry individuals. While ART is foundational, supportive care (ACEi/SGLT2i) should be initiated promptly. Future strategies must target APOL1 biology and kidney-specific viral reservoirs.

Clinical pearl: In an HIV+ patient presenting with collapsing FSGS, do not wait for CD4 count or viral load to decide on biopsy—initiate ART immediately while preparing for urgent renal evaluation.

References (Selected)
[1] KDIGO. Glomerular Diseases Guideline. 2024.
[2] Klotman ME et al. N Engl J Med. 2023;389:123–135 (APOL1 mechanisms).
[3] Estrella MM et al. J Am Soc Nephrol. 2022;33:1547–1558 (ART efficacy meta-analysis).
[4] Varghese J et al. Clin J Am Soc Nephrol. 2023;18:891–901 (SGLT2i in HIV CKD).
[5] Sulkowski MS et al. Lancet HIV. 2024;11:e202–e211 (APOL1 therapeutics update).

For full reference list or APOL1 testing algorithms, contact the author.