Description

• 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

Epidemiology

Incidence

• Annual incidence: ranges from 3 to 27/100,000 children and 0.8 to 1.8/100,000 adults
• Mean age: 6 years; 90% of patients with HSP are <10 years of age; however, has been reported in patients age 6 months to 75 years old
• Gender: Male-to-female ratio is between 1.2:1 and 1.8:1.
• Race/ethnicity: most common in Caucasians and Asians, less common among African Americans

Prevalence

• Annual prevalence: 10 to 22/100,000 persons
• Year-round occurrence; more common in fall

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.
• IgA-containing immune complex deposition results in small vessel inflammation which leads to fibrosis and necrosis within skin, intestinal mucosa, joints, and kidneys.
• No single etiologic agent has been identified; however, there are some associations (listed below) and a popular theory is one of a multihit model leading to HSP-associated glomerulonephropathy.
  • Infections are suggested by prevalence in the fall and a common upper respiratory infection (URI) prodrome. Associated pathogens 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, herpes simplex, varicella, Campylobacter, methicillin-resistant Staphylococcus aureus.
  • Drugs are most often associated with adults with HSP: acetaminophen, angiotensin-converting enzyme inhibitors (ACEI), angiotensin II receptor antagonists (ARB), some antibiotics including clarithromycin quinolones, etanercept, codeine, nonsteroidal anti-inflammatory drugs.
  • Vaccinations are rarely reported in association with HSP; however, there are some reports surrounding administration of MMR (measles, mumps, rubella), pneumococcal, meningococcal, influenza and hepatitis B immunizations.

Genetics
Associated with α₁-antitrypsin deficiency, familial Mediterranean fever, HLA-A2, HLA-A11, HLA-B35, HLA-DRB1, renin-angiotensin and nitric oxide synthase polymorphisms

Commonly Associated Conditions

• Malignancy: this is rare and the greatest association is with solid tumors, including lymphoma, prostate cancer, and non–small cell lung cancer, but also multiple myeloma.
• Studies suggest a possible relationship with H. pylori infection (1) and immune-related disorders (food allergy, drug allergy, inflammatory bowel disease).