Workup for Henoch-Schönlein Purpura (HSP)
The diagnosis of HSP is primarily clinical and requires palpable purpura plus at least one of the following: renal involvement (hematuria/proteinuria), arthralgia/arthritis, or abdominal pain—with urinalysis being the single most critical initial test to assess for nephritis. 1, 2
Essential Diagnostic Workup
Immediate Laboratory Testing
Urinalysis with microscopy is mandatory at presentation to assess for glomerulonephritis, specifically looking for: 1, 2
- Proteinuria (quantify amount)
- Red blood cell casts (indicate glomerular involvement)
- Dysmorphic red blood cells (confirm glomerular origin)
- Hematuria
Basic metabolic panel including: 1, 2
- Blood urea nitrogen (BUN)
- Serum creatinine (assess renal function)
- Electrolytes
Complete blood count with platelets to rule out thrombocytopenia (platelets should be normal in HSP, distinguishing it from other purpuric conditions). 1
Blood pressure measurement is essential, as hypertension indicates more severe renal involvement and worse prognosis. 1, 2
Optional Confirmatory Testing
Skin biopsy with immunofluorescence should be performed when the clinical presentation is incomplete or atypical, as IgA deposits in vessel walls are the sine qua non for diagnosis—this prevents both missed diagnoses and unnecessary follow-up. 3 The biopsy shows leukocytoclastic vasculitis with predominant IgA deposition in vessel walls. 4
Imaging Considerations
Renal ultrasound is the preferred initial imaging to assess kidney size and anatomy, particularly if renal biopsy is being considered for severe nephritis (crescentic disease, nephrotic syndrome, or deteriorating kidney function). 1
When to Perform Renal Biopsy
Renal biopsy is indicated for: 2
- Decreased renal function at presentation
- Severe nephrotic syndrome (proteinuria >3.5 g/day)
- Nephritic syndrome
- Deteriorating kidney function despite treatment
Critical Monitoring Protocol
Day 7 urinalysis is prognostically crucial—a normal urinalysis on day 7 has a 97% negative predictive value for normal renal outcome, allowing risk stratification of patients. 5
All HSP patients require 6-month monitoring with: 5
- Regular urinalysis (weekly initially, then monthly)
- Blood pressure checks
- Serum creatinine monitoring
- Quantification of proteinuria
Patients with abnormal day 7 urinalysis require more intensive monitoring as they are at higher risk for developing nephritis. 5
Common Pitfalls to Avoid
Do not assume HSP is benign in adults—adults have significantly worse outcomes than children, with only 20% achieving complete clinical remission and 11% progressing to end-stage renal disease. 6 Older patients are at higher risk of requiring renal referral. 5
Do not delay urinalysis—renal involvement can occur years after initial presentation, and silent chronic renal failure can develop without appropriate monitoring. 3
Do not use NSAIDs for pain control in HSP patients with any renal involvement, as they can cause acute kidney injury; use acetaminophen as first-line analgesic instead. 2
Do not start prophylactic corticosteroids at HSP onset to prevent nephritis—moderate quality evidence (Level 1B) shows no benefit in preventing nephritis development. 1, 2