A 28-year-old woman from Delhi presents with a 6-month history of arthralgia, photosensitive malar rash, and oral ulcers. Laboratory investigations show ANA 1:640 (homogeneous pattern), anti-dsDNA antibodies positive, low C3 and C4 levels, and urinalysis reveals 2+ proteinuria with RBC casts. What is the most appropriate next step in management?

Explanation

## Clinical Context This patient meets ACR/EULAR criteria for SLE (malar rash, photosensitivity, oral ulcers, arthralgia, positive ANA, anti-dsDNA, low complement) with **active lupus nephritis** (proteinuria, RBC casts, low complement). ## Management Algorithm for Lupus Nephritis ```mermaid flowchart TD A["SLE with proteinuria + RBC casts<br/>+ low C3/C4"]:::outcome --> B{"Suspected lupus nephritis?"} B -->|Yes| C["Start hydroxychloroquine<br/>+ corticosteroids<br/>+ refer for renal biopsy"] B -->|No| D["Conservative management"] C --> E["Biopsy guides induction therapy<br/>class I-II: corticosteroids alone<br/>class III-IV: cyclophosphamide/MMF"] E --> F["Tailor immunosuppression<br/>based on histology"] style A fill:#e1f5ff style C fill:#c8e6c9 style E fill:#fff9c4 ``` ## Key Point: **Renal biopsy is the gold standard for lupus nephritis classification and guides induction therapy choice.** However, **immediate initiation of hydroxychloroquine and corticosteroids is appropriate while awaiting biopsy** — these are safe, non-immunosuppressive baseline therapies that do not interfere with histological interpretation. ## High-Yield: - **Hydroxychloroquine** (200–400 mg/day) is the cornerstone of SLE management — reduces flares, improves renal outcomes, and is safe in pregnancy. - **Low-dose prednisolone** (0.5–1 mg/kg/day initially) controls inflammation while biopsy is arranged. - **Renal biopsy classification** (WHO/ISN-RPS): - Class I–II: corticosteroids alone - Class III–IV: induction therapy (cyclophosphamide or mycophenolate mofetil + corticosteroids) - Class V: mycophenolate or cyclophosphamide ## Clinical Pearl: Low C3/C4 with active urinary findings is a red flag for proliferative lupus nephritis (Class III–IV). Biopsy is **not** delayed by starting hydroxychloroquine and corticosteroids — it should be arranged urgently (within 1–2 weeks) to guide induction therapy escalation. ## Warning: ~~Starting NSAIDs in the presence of proteinuria and RBC casts is contraindicated~~ — NSAIDs can worsen renal function and are not appropriate monotherapy for active lupus nephritis.