What are the diagnostic criteria and management for Henoch-Schönlein Purpura (HSP)?

Henoch-Schönlein Purpura (HSP): Diagnosis and Clinical Features

What is HSP?

HSP, now formally termed IgA vasculitis (Henoch-Schönlein purpura), is an IgA-mediated systemic small-vessel vasculitis that predominantly affects children, characterized by palpable purpura, arthritis/arthralgia, abdominal pain, and renal involvement. 1, 2, 3

• HSP is the most common form of systemic vasculitis in children, with a global incidence of 10-20 cases per 100,000 children annually 3
• Approximately 90% of cases occur in children aged 2-10 years, with peak incidence at 4-7 years 3
• The pathophysiology centers on IgA1-mediated immune complex deposition in small vessel walls, likely related to abnormal glycosylation of IgA1 molecules 4

Clinical Presentation: The Four Cardinal Features

The diagnosis requires palpable purpura PLUS at least one of the following: 3

1. Cutaneous Manifestations (100% of cases)

• Non-thrombocytopenic palpable purpura is the hallmark and appears in all patients 1, 4
• Typically distributed on lower extremities and buttocks in a dependent pattern 1
• The rash may not appear immediately at presentation, which can delay diagnosis 5

2. Joint Involvement (82% of cases)

• Migratory polyarthralgias or frank arthritis affecting knees and ankles predominantly 5, 4
• Joint symptoms are typically self-limited and non-erosive 4

3. Gastrointestinal Involvement (63% of cases)

• Diffuse abdominal pain from bowel angina 2, 3
• Gastrointestinal bleeding occurs in 33% of patients 4
• Can include duodenal involvement documented endoscopically 5

4. Renal Involvement (40% of cases)

• Hematuria and/or proteinuria 2, 3
• Renal involvement is the most critical prognostic factor, as HSP nephritis leads to chronic renal failure in up to 20% of pediatric patients after 20 years in selected series 6
• Risk exceeds 50% when initial presentation combines nephrotic and nephritic syndromes 6

Diagnostic Approach

Formal Diagnostic Nomenclature

The American Society of Nephrology recommends writing the final diagnosis as "IgA vasculitis (Henoch-Schönlein purpura)" with specification of organ involvement pattern and histopathological confirmation showing IgA-dominant immune complex deposition. 1

• Document presence or absence of nephritis, and specify severity of renal involvement (mild hematuria vs. nephrotic-nephritic syndrome) 1
• Include patient age and presence of crescentic glomerulonephritis, as these affect prognosis 1

Histopathological Confirmation

Skin biopsy should be performed systematically in cases of clinical suspicion to confirm the diagnosis through histological and immunofluorescence studies. 6

• Skin biopsy demonstrates leukocytoclastic vasculitis with IgA-dominant immune deposits in vessel walls 1, 2, 6
• Renal biopsy (when indicated) shows mesangial proliferative glomerulonephritis with IgA deposits 1
• Finding IgA deposits in vessel walls associated with small-vessel vasculitis is sine qua non for diagnosis 6

Critical pitfall: When based on clinical signs alone, HSP diagnosis can be missed, particularly when the clinical picture is incomplete or renal signs manifest years after initial symptoms, risking silent chronic renal failure 6

Laboratory Findings

• Elevated serum IgA concentrations and IgA-containing circulating immune complexes support the diagnosis 4
• HSP is associated with abnormalities involving IgA1 exclusively, not IgA2 4
• Normal platelet count distinguishes HSP from thrombocytopenic purpura 5, 4

Differential Diagnosis Exclusion

Document negative ANCA and anti-GBM antibody tests, plus normal complement levels to exclude other vasculitides. 1

• Other non-IgA-related leukocytoclastic vasculitides can mimic HSP and confound diagnosis 6
• ANCA-associated vasculitis must be systematically excluded 1

Clinical Course and Prognosis

• Most cases are self-limited with average disease duration of 4 weeks 3
• One-third of patients experience one or more recurrences of symptoms 4
• Long-term prognosis depends directly on severity of renal involvement 3, 4
• Renal risk persists even for mild initial symptoms or after apparent complete recovery 6
• Renal signs can become manifest years after initial presentation, necessitating long-term follow-up 6

Key Diagnostic Pitfalls to Avoid

• Do not rely solely on clinical presentation: The characteristic purpuric rash may emerge days after other symptoms, delaying recognition 5
• Do not assume complete recovery: Patients require long-term monitoring even after apparent resolution, as renal involvement can develop late 6
• Do not overdiagnose: Systematic skin biopsy prevents unnecessary follow-up in patients without true HSP 6
• Do not underestimate renal risk: Even mild initial renal symptoms carry persistent risk for chronic kidney disease 6