Description

• Henoch-Schönlein purpura (HSP), also called immunoglobulin A vasculitis, is an immunologically mediated, purpuric, nonthrombocytopenic, and systemic vasculitis involving the small blood vessels of the skin, gastrointestinal (GI) tract, joints, and kidneys.
• Diagnosis is defined by the presence of at least two of the following classification criteria:
  • Palpable purpura (not related to thrombocytopenia)
  • Age ≤20 years at onset
  • Abdominal pain
  • Biopsy showing granulocytic infiltrates in the walls of arterioles or venules

Epidemiology

• One of the most common acute vasculitides in childhood
• Occurs most frequently between the ages of 3 and 15 years
• Incidence of 13.5 cases per 100,000 children per year
• Male predominance
• Seasonal variation, with most cases occurring primarily in the winter

Risk Factors

Pathophysiology

• Predominantly an IgA-mediated immune response to antigen and operates through the alternative complement pathway
• There is a characteristic vascular deposition of IgA in affected organs.
• IgA immune deposits affect the small vessels, predominantly capillaries, arterioles, and venules.
• Studies suggest that renal injury in HSP is due to galactose-deficient IgA1 that is recognized by antiglycan antibodies, leading to the formation of circulating immune complexes and their mesangial deposition
• Renal biopsy shows proliferative glomerulonephritis with an increase in endothelial and mesangial cells, ranging from focal and segmental lesions to severe crescentic disease.

Etiology

• Genetically predisposed hosts may be susceptible to the following associations and triggers.
• Many cases are preceded by an upper respiratory tract infection (URI), particularly β-hemolytic streptococci.
• Other infectious associations include viral infections (varicella, rubella, rubeola, hepatitis A and B), Mycoplasma pneumoniae, Bartonella henselae, and Helicobacter pylori.
• Vaccinations, drug exposure, and insect bites have been implicated as possible triggers.