The disorders in this category include Henoch-Schönlein purpura (HSP) and Wegener's granulomatosis.
HSP most commonly affects children between the ages of three and 12 years.
About 50-60 percent of children with HSP were diagnosed with strep throat or another upper respiratory infection two to three weeks before the onset of the vasculitis.
Although the ultimate cause of HSP was unknown as of 2004, the disease is preceded by an acute upper respiratory infection in at least half the children diagnosed with it.
A characteristic finding in children diagnosed with HSP is higher levels of immunoglobulin A (IgA) in the blood and deposits of IgA on the walls of the child's blood vessels.
HSP is an acute but self-limited illness characterized by a low-grade fever (around 100.4°F[38°C]), purpura, joint pains (usually in the ankles and knees), abdominal pain, bleeding in the digestive tract, and inflammation of the kidneys.
Boys with HSP often have inflammation of the testicles.
The prognosis for children with HSP is generally good, as the disease usually goes away by itself even without treatment; however, about a third of patients have recurrences.
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