Henoch-Schonlein Purpura (aka. Anaphylactoid purpura) is a small vessel vasculitis.

Background:

• most commonly diagnosed vasculitide in childhood
• age range 3-15 years, mean age 4yo, mostly <7yo (75% cases)
• more cases in Winter and Spring months
• boys more commonly than girls (2:1)
• IgA-mediated leukoclastic vasculitis

Clinical Features:

• Rash: progresses to petechiae, purpura; occurs on lower extremities and buttocks in dependent areas
• Joints: arthritis/arthralgia mainly of large joints (knees, ankles)
• GI: colicky abdominal pain, may occur with melena (33%) or less likely, hematemesis; ultrasound for intussusception (2-14%)
• Renal: microscopic hematuria with/without proteinuria; usually transient but may lead to progressive renal disease in patients with more severe, persistent symptoms
• Orchitis and/or angioedema may also occur

Etiology:

• unknown
• preceding URI (50%)
• associated with bacteria (Strep pyogenes, Legionella, Mycoplasma), viruses (EBV, CMV, parvovirus), drugs (penicillin, cephalosporins), and insect bites

Diagnosis:

• clinical features
• lab studies that are helpful but nonspecific: high WBC, high ESR, high IgA, normal platelet and coagulation studies

Treatment:

• supportive care, may last up to 4 weeks
• steroids may be helpful but evidence has not shown true benefit
• recurrence happens in 40% of cases