✅ Model Answer:
• Diagnosis: Lupus nephritis – likely class V (membranous) or class IV (diffuse proliferative).
• Evidence: Nephrotic-range proteinuria (P/C 2.5), hypoalbuminemia (2.8), low C3 and C4 (complement consumption), malar rash, joint pain – systemic lupus erythematosus (SLE).
• Next step: Renal biopsy to classify lupus nephritis (ISN/RPS classification). Start hydroxychloroquine, ACE inhibitor/ARB. Treat based on class: class III/IV – mycophenolate mofetil or cyclophosphamide + steroids; class V – steroids + calcineurin inhibitor or mycophenolate.

✅ Model Answer:
• Systemic lupus erythematosus (SLE): An autoimmune disease characterized by the production of autoantibodies against nuclear antigens (ANA, anti-dsDNA).
• Renal involvement: Immune complexes (DNA-anti-DNA) deposit in the glomeruli → complement activation (low C3/C4) → glomerular inflammation → proteinuria, hematuria, and progressive CKD.
• ISN/RPS classification:
- Class I: Minimal mesangial.
- Class II: Mesangial proliferative.
- Class III: Focal proliferative (<50% glomeruli).
- Class IV: Diffuse proliferative (>50% glomeruli) – most severe.
- Class V: Membranous (subepithelial deposits).
- Class VI: Advanced sclerosing.
• Pathology: "Full house" immunofluorescence (IgG, IgM, IgA, C3, C1q) on renal biopsy.

✅ Model Answer:
• Renal features:
- Proteinuria: Subnephrotic to nephrotic range (P/C >0.2 to >2.0).
- Hematuria: Microscopic or gross (RBCs, RBC casts).
- Hypertension.
- Renal insufficiency (elevated creatinine).
- Nephrotic syndrome (in class V).
- Nephritic syndrome (hematuria, HTN, renal insufficiency – in class III/IV).
• Systemic SLE features:
- Malar rash (butterfly rash).
- Arthritis.
- Serositis.
- Hematologic: Anemia, leukopenia, thrombocytopenia.
- Photosensitivity, oral ulcers.
- Anti-dsDNA, ANA positive.
- Low complement (C3, C4).

✅ Model Answer:
• Serologic tests:
- ANA: Positive (>1:80).
- Anti-dsDNA: Positive (highly specific for SLE).
- Complement (C3, C4): Low (active disease).
- ESR, CRP: Elevated.
- CBC: Anemia, leukopenia, thrombocytopenia.
• Urine studies:
- Urine P/C ratio: Nephrotic-range (if class V) or subnephrotic.
- Urinalysis: Hematuria, RBC casts, pyuria.
• Renal biopsy: Gold standard for diagnosis and classification.
• Other: Anti-Smith, anti-RNP, anti-Ro/La (for SLE diagnosis).
• Monitor: BP, creatinine, proteinuria.

✅ Model Answer:
• General measures:
- Hydroxychloroquine: 5-6 mg/kg/day (all SLE patients).
- ACE inhibitor/ARB: For proteinuria and BP control.
- Sunscreen, UV protection.
- Vaccinations: Pneumococcal, influenza (avoid live vaccines during immunosuppression).
• Immunosuppression (based on biopsy class):
- Class III/IV (proliferative):
• Induction: Mycophenolate mofetil (MMF) or cyclophosphamide + high-dose corticosteroids.
• Maintenance: MMF or azathioprine + low-dose steroids.
- Class V (membranous):
• Steroids + calcineurin inhibitor (tacrolimus/cyclosporine) or MMF.
- Class I/II: Hydroxychloroquine + ACE inhibitor; steroids if proteinuria develops.
• Biologics: Rituximab, belimumab (for refractory lupus).
• Monitor: Proteinuria, BP, creatinine, complement, anti-dsDNA.

✅ Model Answer:
• Chronic kidney disease (CKD): 10-30% progress to ESKD within 10 years.
• Nephrotic syndrome: Edema, thromboembolism, infections.
• Hypertension.
• Thromboembolism: Renal vein thrombosis (especially in nephrotic syndrome).
• Infections: Due to immunosuppression.
• Relapse: Common (requires re-biopsy and treatment adjustment).
• Pregnancy complications: Pre-eclampsia, fetal loss.
• Drug toxicity: Cyclophosphamide (hemorrhagic cystitis, infertility), steroids (osteoporosis, weight gain).

✅ Model Answer:
• Prognosis:
- Improved with early diagnosis and aggressive immunosuppression.
- Class III/IV: Worse prognosis (30% ESKD in 10 years).
- Class V: Better prognosis (less progression to ESKD).
- Children: More aggressive disease but better response to treatment.
- Renal transplantation: Successful; recurrence is rare.
• Long-term follow-up:
- Monitor proteinuria, BP, creatinine.
- Monitor complement, anti-dsDNA.
- Monitor for drug toxicity.
- Vaccinations.
- Psychosocial support.

✅ Model Answer:
• Indications:
- Proteinuria (P/C >0.5) or nephrotic-range proteinuria.
- Hematuria with RBC casts.
- Declining renal function (rising creatinine).
- To guide treatment (class I-VI determines therapy).
- To monitor response (repeat biopsy if treatment failure).
• Histology:
- Light microscopy: Mesangial proliferation, endocapillary proliferation, crescents, sclerosis.
- Immunofluorescence: "Full house" (IgG, IgM, IgA, C3, C1q) along capillary loops and mesangium.
- Electron microscopy: Subendothelial, mesangial, or subepithelial deposits.
• Classification: ISN/RPS classes I-VI – determines treatment.
• Prognosis: Class IV has the worst prognosis; class V has better prognosis.