Article Text

Diagnostic issues in systemic lupus erythematosis
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1. N Sofat,
2. C Higgens
1. Northwick Park and St Marks' Hospital, Watford Road, Harrow, Middlesex HA1 3UJ, UK
1. Dr Higgens c.higgens{at}ic.ac.uk

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A 24 year old woman was diagnosed with systemic lupus erythematosis (SLE) based on a few months' history of a photosensitive skin rash, predominantly on her face, arthralgia involving both hands and wrists, a positive antinuclear antibody (ANA) test and a raised antinative double stranded DNA antibody binding level. She was treated with oral hydroxychloroquine 400 mg daily and short courses of prednisolone during flare-ups.

She was reviewed in clinic for her regular follow up appointment when she was found to be hypertensive on repeated measurements of her blood pressure, an average value being 150/90 mm Hg. She was also urine dipstick positive for blood and protein.

## Questions

(1) Which three tests would you ask for next from the clinic?

(a) 24 hour urine collection for protein

(b) Measurement of erythrocyte sedimentation rate (ESR) and C reactive protein (CRP)

(c) Urgent urine microscopy for evidence of casts

(d) Measurement of DNA binding titres

(e) Renal tract ultrasound scan

(f) Measurement of serum urea, electrolytes, and creatinine

(2) What instructions do you give to a patient in order to perform a 24 hour urine protein collection?

(3) Can a 24 hour urine collection under/over estimate the glomerular filtration rate?

(4) What other tests (apart from 24 hour urine creatinine clearance) are available to measure the glomerular filtration rate?

The patient had a 24 hour urinary protein collection, which showed a 24 hour protein measurement of 1.8 g. There was no evidence of cellular casts on urine microscopy. Her blood results were as below (normal values are in parentheses):

• Sodium 134 mmol/l (135–145)

• Potassium 4.5 mmol/l (3.5–5.0)

• Urea 7.0 mmol/l (2.5–6.7)

• Creatinine 173 μmol/l (70–115)

• Haemoglobin 108 g/l (115–160)

• White cell count 4.5 × 109/l (4.0–11.0)

• Platelets 130 × 109/l (150–400)

### IMMUNOLOGY RESULTS

• C3 0.30 g/l (0.77–1.63)

• C4 <0.10 g/l (14–42)

• ESR 42 mm/hour

• CRP 40 mg/l (0–10)

• ANA positive at 1:2560

• DNA binding 1000 IU/ml (0–30)

(5) What is the likely cause of this clinical picture and results?

(a) Urinary tract infection

(b) Dehydration

(c) Essential hypertension

(d) SLE associated lupus nephritis

(e) Renal amyloidosis

(6) If this patient had persistently lowered complement levels from the time of her diagnosis, both during remission and relapses of her SLE, what other diagnosis would you have to consider?

(7) Which investigation would you like to do next in order to obtain diagnostic and prognostic information regarding the cause of this women's renal impairment?

(a) Intravenous urogram

(b) Renal biopsy

(c) Renal tract ultrasound scan

(d) Repeat urea and electrolytes

(e) Renal EDTA clearance

The result of the renal biopsy showed diffuse proliferative glomerulonephritis (World Health Organisation (WHO) grade IV). Figure 1is an illustration of the changes seen.

Figure 1

Light microscopy of renal biopsy showing proliferative changes throughout the glomerulus consistent with WHO class IV lupus nephritis (haematoxylin and eosin stain).

The patient was initially treated with pulsed methylprednisolone but her renal function did not improve. She consented for treatment with monthly pulsed cyclophosphamide for six months, after which her renal function improved and she remained normotensive.

(8) What issues would you have to consider and counsel the patient for when gaining consent from a young woman for treatment with cyclophosphamide?

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