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- Henoch-Schönlein purpura (HSP) is a nonthrombocytopenic, predominantly IgA-mediated, small vessel vasculitis that affects multiple organ systems and occurs in both children and adults.
- HSP is often self-limited, with the greatest morbidity and mortality attributable to long-term renal damage.
- Characterized by a tetrad of purpuric skin lesions, arthralgia, abdominal pain, and nephropathies
- Annual incidence: 135/1 million children and 3.4 to 14.3/1 million adults
- Mean age of patients affected is 6 years; 90% <10 years of age but has been reported in patients age 6 months to 75 years old
- Gender: Male-to-female ratio is 1.2:1.
- Race/ethnicity: most common in Caucasians and Asians, less common among African Americans
- Annual prevalence: 10 to 22/100,000 persons
- Year-round occurrence; more common in late fall to early spring
Etiology and Pathophysiology
- Autoimmune disorder in which IgA production is increased in response to trigger(s), IgA1 immune complexes then activate the complement pathway, leading to production of inflammatory cytokines and chemokines.
- Immune complex deposition results in small vessel inflammation; fibrosis; and necrosis within skin, intestinal mucosa, joints, and kidneys.
- No single etiologic agent has been identified.
- Known triggers include infection, drugs, vaccinations, and insect bites.
- Infectious antigens include (but are not limited to) group A Streptococcus (may be present in up to 30% of HSP-associated nephritis), parvovirus B19, Bartonella henselae, Helicobacter pylori, Haemophilus parainfluenzae, coxsackievirus, adenovirus, hepatitis A and B viruses, Mycoplasma, Epstein-Barr virus, varicella, Campylobacter, methicillin-resistant Staphylococcus aureus.
- Drugs: acetaminophen, quinolones, etanercept, codeine, clarithromycin
- Vaccinations: MMR (measles, mumps, rubella), pneumococcal, meningococcal, influenza, hepatitis B
Associated with α1-antitrypsin deficiency, familial Mediterranean fever, HLA-DRB1*01, HLA-B35