A 32-year-old woman with known SLE presents with persistent proteinuria (2.5 g/day), hematuria, and rising serum creatinine (1.8 mg/dL). She is ANA positive and anti-dsDNA positive. Which investigation is most appropriate to assess the severity and type of lupus nephritis?

Question

Accepted Answer

A. Renal biopsy with light microscopy, immunofluorescence, and electron microscopy. ## Diagnostic Approach to Lupus Nephritis

**Key Point:** Renal biopsy with light microscopy (LM), immunofluorescence (IF), and electron microscopy (EM) is the gold standard for diagnosing and classifying lupus nephritis.

### Why Renal Biopsy?

**High-Yield:** Lupus nephritis is classified into 6 WHO classes (I–VI) based on histopathological findings. Biopsy is essential to:
1. Confirm lupus nephritis diagnosis
2. Determine the class and stage (activity and chronicity indices)
3. Guide treatment intensity and prognosis
4. Identify reversible vs. irreversible changes

### WHO Classification of Lupus Nephritis

| Class | Histology | LM | IF Pattern | Prognosis |
| --- | --- | --- | --- | --- |
| I | Minimal | Normal | Negative or minimal | Excellent |
| II | Mesangial | Mesangial proliferation | IgG, IgA, IgM in mesangium | Good |
| III | Focal proliferative | <50% glomeruli involved | Granular IgG, C3 (full house) | Fair |
| IV | Diffuse proliferative | >50% glomeruli involved | Granular IgG, C3 (full house) | Poor |
| V | Membranous | Thickened GBM | Granular IgG along GBM | Variable |
| VI | Advanced sclerosis | Global sclerosis | Minimal deposits | Poor |

**Clinical Pearl:** The "full house" pattern on immunofluorescence (IgG, IgA, IgM, C3, C1q all positive) is pathognomonic for SLE and helps distinguish it from other glomerulonephritides.

### Diagnostic Algorithm for Lupus Nephritis

```mermaid
flowchart TD
  A[SLE patient with proteinuria/hematuria]:::outcome --> B[Quantify proteinuria and assess renal function]:::action
  B --> C{Significant renal involvement?}:::decision
  C -->|Yes| D[Perform renal biopsy]:::action
  D --> E[Light microscopy classification]:::action
  E --> F[Immunofluorescence: full house pattern?]:::decision
  F -->|Yes| G[Lupus nephritis confirmed]:::outcome
  D --> H[Determine WHO class I-VI]:::action
  H --> I[Assess activity and chronicity indices]:::action
  I --> J[Guide immunosuppressive therapy]:::action
  C -->|No| K[Monitor with serology and urinalysis]:::action
```

**Mnemonic:** **FULL HOUSE** immunofluorescence = **F**ibrinogen, **U**nknown (C1q), **L**ight chain (IgG, IgA, IgM), **L**ow density (C3) — all positive in SLE.

Answer

B. 24-hour urine protein estimation and serum complement levels

Answer

C. Serum creatinine and blood urea nitrogen levels alone

Answer

D. Urinary casts and proteinuria quantification by dipstick

A 32-year-old woman with known SLE presents with persistent proteinuria (2.5 g/day), hematuria, and rising serum creatinine (1.8 mg/dL). She is ANA positive and anti-dsDNA positive. Which investigation is most appropriate to assess the severity and type of lupus nephritis?

Explanation

Diagnostic Approach to Lupus Nephritis

Why Renal Biopsy?

WHO Classification of Lupus Nephritis

Diagnostic Algorithm for Lupus Nephritis

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Class	Histology	LM	IF Pattern	Prognosis
I	Minimal	Normal	Negative or minimal	Excellent
II	Mesangial	Mesangial proliferation	IgG, IgA, IgM in mesangium	Good
III	Focal proliferative	<50% glomeruli involved	Granular IgG, C3 (full house)	Fair
IV	Diffuse proliferative	>50% glomeruli involved	Granular IgG, C3 (full house)	Poor
V	Membranous	Thickened GBM	Granular IgG along GBM	Variable
VI	Advanced sclerosis	Global sclerosis	Minimal deposits	Poor