Typical Biopsy Findings in Henoch-Schönlein Purpura (HSP)
The definitive histopathologic diagnosis of HSP requires demonstration of leukocytoclastic vasculitis on skin biopsy with IgA deposits in vessel walls on direct immunofluorescence. 1
Essential Histopathologic Features
Light Microscopy Findings
- Leukocytoclastic vasculitis affecting small vessels in the upper dermis is the hallmark finding 2, 1
- The vasculitis shows neutrophilic infiltration with nuclear debris (leukocytoclasia) surrounding and infiltrating vessel walls 3
- Small vessel involvement is limited to capillaries and postcapillary venules in the superficial dermis 2
Direct Immunofluorescence (Critical for Diagnosis)
- IgA deposits in vessel walls are pathognomonic and represent the sine qua non for HSP diagnosis 1
- These IgA deposits distinguish HSP from other forms of leukocytoclastic vasculitis that may appear identical on routine histology 1
- Without demonstrating IgA deposits, the diagnosis remains uncertain and patients risk being misdiagnosed 1
Biopsy Technique Recommendations
Skin Biopsy Protocol
- Perform skin biopsy on fresh purpuric lesions (ideally less than 24-48 hours old) for optimal diagnostic yield 1
- Submit one specimen for routine histopathology (formalin-fixed) to identify leukocytoclastic vasculitis 2
- Submit a second specimen unfixed for direct immunofluorescence to detect IgA deposits—this is mandatory and cannot be performed on formalin-fixed tissue 1
Alternative Biopsy Sites When Skin Findings Are Atypical
- Gastrointestinal mucosal biopsies can reveal IgA deposits even when skin biopsy is negative or when cutaneous lesions are absent 4
- Take biopsies from both visibly involved AND normal-appearing gastrointestinal mucosa, as IgA deposits may be present in endoscopically normal tissue 4
- GI biopsies show the same leukocytoclastic vasculitis pattern affecting small vessels in the lamina propria 3, 5
Critical Diagnostic Pitfalls to Avoid
Common Errors
- Never rely on clinical diagnosis alone without histopathologic confirmation, as this leads to both missed diagnoses and overdiagnosis with inappropriate long-term follow-up 1
- Failing to request direct immunofluorescence results in an incomplete diagnosis, as leukocytoclastic vasculitis without IgA deposits could represent other vasculitides 1
- Biopsying old lesions (>48-72 hours) may show only nonspecific changes without diagnostic features 1
When Skin Biopsy Is Negative
- If clinical suspicion remains high but skin biopsy shows no IgA deposits, consider gastrointestinal mucosal biopsy as IgA deposits may be present in GI mucosa despite negative skin findings 4
- This is particularly important in atypical presentations where abdominal symptoms precede cutaneous manifestations 5, 4
Clinical Context for Interpretation
The biopsy findings must be interpreted alongside the clinical presentation of palpable purpura (typically on lower extremities and buttocks), with or without arthralgia, abdominal pain, and renal involvement 2, 3. In severe cases, the purpura may evolve into hemorrhagic bullous lesions, but the underlying histopathology remains leukocytoclastic vasculitis with IgA deposits 2.