A 28-year-old woman from Delhi presents with a 6-month history of polyarthralgia affecting the small joints of her hands, morning stiffness lasting 2 hours, and a malar rash that worsens in sunlight. She reports recurrent oral ulcers and has noticed hair loss over the past 3 months. On examination, she has a butterfly rash across the cheeks and nasal bridge, and non-erosive arthritis of the PIP and MCP joints. Laboratory investigations show: ANA 1:640 (homogeneous), anti-dsDNA 180 IU/mL (normal <70), anti-Smith antibody positive, complement C3 78 mg/dL (normal 90–180), ESR 68 mm/hr, and urinalysis shows 2+ proteinuria with RBC casts. Which of the following is the most appropriate next step in management?

Explanation

## Clinical Diagnosis **Key Point:** This patient meets ACR/EULAR 2019 criteria for SLE with: - Malar rash (photosensitive) - Non-erosive arthritis (small joints) - Oral ulcers - Hair loss (alopecia) - ANA homogeneous pattern - Anti-dsDNA and anti-Smith positivity - Complement consumption (low C3) - Proteinuria with RBC casts (lupus nephritis WHO Class III/IV) ## Lupus Nephritis Risk Stratification | Finding | Significance | |---------|-------------| | Proteinuria 2+ with RBC casts | Indicates active glomerulonephritis | | Low complement C3 | Marker of active disease and immune complex deposition | | Anti-dsDNA positive | Strongly associated with lupus nephritis | | Elevated creatinine (not stated but proteinuria present) | Warrants urgent renal assessment | ## Management Algorithm for SLE with Lupus Nephritis ```mermaid flowchart TD A[SLE + Proteinuria + RBC casts]:::outcome --> B{Suspected lupus nephritis?}:::decision B -->|Yes| C[Confirm with renal biopsy]:::action C --> D{WHO Class?}:::decision D -->|Class I-II| E[Hydroxychloroquine + NSAIDs ± low-dose prednisolone]:::action D -->|Class III-IV| F[Hydroxychloroquine + Prednisolone 0.5-1 mg/kg/day]:::action F --> G[Add immunosuppression: CYC or MMF]:::action E --> H[Monitor proteinuria, creatinine, complement]:::action G --> H ``` **High-Yield:** The presence of RBC casts with proteinuria in an SLE patient constitutes probable lupus nephritis and mandates renal biopsy for: - Confirmation of diagnosis - WHO classification (determines induction therapy intensity) - Assessment of chronicity (fibrosis, sclerosis) — guides prognosis **Clinical Pearl:** Hydroxychloroquine is the backbone of all SLE therapy — it reduces flares, improves long-term outcomes, and is safe in pregnancy. It should NOT be withheld pending remission. ## Rationale for Option 2 (Correct Answer) 1. **Hydroxychloroquine 400 mg daily** — foundational therapy for all SLE manifestations; reduces flare risk and improves survival. 2. **Prednisolone 0.5–1 mg/kg/day** — standard induction dose for active lupus nephritis; tapered after 4–12 weeks based on response. 3. **Renal biopsy** — essential to confirm lupus nephritis, determine WHO class, and guide choice of immunosuppressive agent (cyclophosphamide vs. mycophenolate mofetil). This approach balances immediate disease control with diagnostic precision. **Warning:** Do not delay hydroxychloroquine waiting for remission — it is protective and should be started immediately. Do not use cyclophosphamide without renal biopsy confirmation, as it carries significant toxicity and may not be necessary for Class III disease.