Workup for HSP in a Child with Rash and No Other Symptoms
For a child presenting with isolated purpuric rash suspicious for HSP, perform urinalysis with microscopy and blood pressure measurement immediately, as renal involvement occurs in 20-50% of cases and represents the primary determinant of long-term morbidity. 1
Essential Initial Laboratory Tests
Urinalysis with microscopy is the single most critical test to assess for glomerulonephritis, specifically looking for: 1, 2
- Proteinuria (quantify if present)
- Red blood cell casts (indicate glomerular involvement)
- Dysmorphic red blood cells (indicate glomerular involvement)
- Hematuria
Blood pressure measurement is essential because hypertension indicates more severe renal involvement and changes management. 1, 2
Basic metabolic panel including BUN and serum creatinine to assess baseline renal function. 1, 2
Complete blood count with platelets to rule out thrombocytopenia (which would suggest ITP rather than HSP, as HSP has normal platelet counts). 2, 3
Clinical Diagnosis
The diagnosis of HSP is clinical and can be made when palpable purpura is present plus at least one of the following: 1, 2
- Renal involvement (hematuria and/or proteinuria)
- Arthralgia/arthritis (bilateral ankle swelling)
- Abdominal pain
In your case with isolated rash, the diagnosis cannot be definitively made yet - you must document whether renal involvement is present through urinalysis. 1, 2
What NOT to Do
Do NOT obtain imaging studies (chest X-ray, abdominal ultrasound, or CT) in an asymptomatic child with isolated rash, as these are not indicated without respiratory or abdominal symptoms. 4
Do NOT perform a renal biopsy at this stage - biopsy is reserved for: 1
- Decreased renal function at presentation
- Severe nephrotic syndrome (proteinuria >3.5 g/day)
- Deteriorating kidney function
Do NOT start corticosteroids prophylactically to prevent nephritis - moderate quality evidence (Level 1B) shows no benefit in preventing nephritis or reducing risk of severe persistent nephritis. 1, 2
Monitoring Protocol
Establish a monitoring schedule for at least 6 months with: 2, 5
- Urinalysis at every clinical visit to detect renal involvement early
- Blood pressure measurements
- Assessment for development of other HSP manifestations (joint pain, abdominal pain)
Common Pitfalls to Avoid
Failing to perform urinalysis at every follow-up visit can lead to delayed detection of renal involvement, which is the primary determinant of long-term morbidity and mortality in HSP. 2
Using NSAIDs (like ketorolac/Toradol) for pain control if renal involvement develops - these can cause acute kidney injury. Use acetaminophen as first-line analgesic instead. 2
Assuming the diagnosis is HSP without documenting at least one additional criterion beyond the rash - the purpura alone is insufficient for diagnosis. 1, 2