Diagnosis: IgA Vasculitis (Henoch-Schönlein Purpura)
The clinical presentation of fever, rash, arthritis, ankle edema, and microscopic hematuria is most consistent with IgA vasculitis (Henoch-Schönlein purpura), making option A the correct diagnosis. 1, 2
Clinical Reasoning
Classic Tetrad of IgA Vasculitis
The patient presents with the characteristic features of IgA vasculitis:
- Palpable purpuric rash: The rash eruption described is consistent with the round or oval palpable purpura that predominantly affects the lower extremities in IgA vasculitis 1
- Arthritis/Arthralgia: Joint involvement, particularly affecting ankles and knees, is a cardinal feature 1, 2
- Renal involvement: Microscopic hematuria indicates glomerulonephritis with mesangial IgA deposits (IgAVN) 1
- Edema: Ankle edema is commonly seen, particularly with renal involvement 3
Why Not SLE?
SLE would typically present with:
- Positive ANA and other autoantibodies (anti-dsDNA, anti-Smith) 4
- More diverse systemic manifestations including malar rash, photosensitivity, serositis 4
- The painful rash on trunk and face described in SLE literature differs from the lower extremity palpable purpura typical of IgA vasculitis 4
Why Not Granulomatosis with Polyangiitis (GPA)?
GPA would more commonly feature:
- Upper respiratory tract involvement: Sinusitis, nasal crusting, epistaxis are hallmark features 5, 6
- Lower respiratory tract disease: Hemoptysis and diffuse alveolar hemorrhage are characteristic 5, 6
- ANCA positivity: Approximately 90% of GPA patients have positive PR3-ANCA or MPO-ANCA 5
- More severe renal disease: Rapidly declining GFR with necrotizing crescentic glomerulonephritis 5
The absence of respiratory symptoms and the presence of the classic tetrad strongly favor IgA vasculitis over GPA 5, 6.
Diagnostic Confirmation
Essential Workup
- Urinalysis: Look for microscopic hematuria with dysmorphic red blood cells and proteinuria (present in this case) 1, 7
- Skin biopsy with direct immunofluorescence: Will demonstrate perivascular IgA deposition, which is pathognomonic 1, 8
- Renal function tests: Monitor for progression to nephrotic syndrome or renal insufficiency 3, 1
- Blood pressure monitoring: Hypertension may develop with worsening nephritis 3
Important Caveat
IgA vasculitis can present without the typical purpuric rash initially, as documented in rare cases where arthritis, edema, and renal involvement precede skin manifestations 3. However, in this case with rash already present alongside the other features, the diagnosis is straightforward.
Prognosis and Monitoring
- Short-term outcome: Depends on severity of gastrointestinal manifestations 1
- Long-term prognosis: Determined by severity of nephritis 1, 7
- Renal symptoms: Proteinuria and hematuria determine long-term prognosis and require close monitoring 7
- Self-limited disease: Most cases in children resolve spontaneously, though adults have higher risk of chronic renal disease 1