Henoch-Schonlein purpura.

Henoch-Schönlein purpura (HSP) is a small vessel vasculitis that annually affects 10 to 20 children per 100,000 population. It is the most common vasculitis of childhood. Although HSP is seen in infancy through adulthood, most documented cases affect children; more than 75% of those diagnosed as having HSP are younger than 10 years, with a peak incidence at 4 to 6 years. White and Asian children are most commonly affected, whereas African American children are least commonly affected. Male predominance among children approaches 2:1. The most recent consensus criteria published in 2010 by the European League Against Rheumatism and the Paediatric Rheumatology European Society state that for diagnosis ofHSP, palpable purpura should be accompanied by at least one of the following: abdominal pain, predominance of IgA deposition on a biopsy specimen, arthritis or arthralgia, or renal involvement indicated by hematuria/ proteinuria. HSP often follows an upper respiratory tract infection, with most cases occurring in the fall and winter. Although many cases do not have a specifically identified infectious trigger, a variety of viral and bacterial agents have been associated with HSP, group A b-hemolytic streptococcus being the most common. Pathogenesis has been linked to IgA1, a subclass of IgA, and its deposition is noted in the glomerulus, the skin, and the blood vessels of the gastrointestinal (GI) tract. Abnormally O-glycosylated IgA1 has been identified in patients with HSP nephritis and in patients with IgA nephropathy, a disease indistinguishable from HSP on renal biopsy. The hallmark of HSP is cutaneous palpable purpura, often involving the lower extremities and buttocks. The appearance of the rash in this pattern reflects its tendency to distribute in pressure-dependent areas, so that in infants the rashmay actually appear in upper body areas, such as the upper extremities or face. Lesions, which arise in crops and last 3 to 10 days, vary in size from petechiae to large, confluent, palpable ecchymoses. Although HSP is largely a clinical diagnosis, a skin biopsy specimen would reveal leukocytoclastic vasculitis or granulocytic infiltration of the small vessels, along with IgA deposition in the vessel walls. A nonpitting edema that involves the scalp, face, trunk, and/or extremities is also common, especially in infants and young children. This swelling does not correlate with the degree of proteinuria or level of serum albumin, although patients withHSPmay also have pitting edema as a consequence of protein loss in the urine. GI involvement is observed in as many as 75% of patients, who often present with diffuse, colicky pain. Commonly, the IgA vasculitis of HSP affects the vessels of the bowel wall, resulting in bleeding from the upper and lower GI tracts and intestinal edema. The bowel edema may also lead to the complication of intussusception; the reported incidence varies from 0.6% to 3.5%. Other major complications, although rare, include bowel ischemia, necrosis, and perforation. Even without frank hemorrhage, the incidence of GI bleeding is high: guaiac-positive AUTHOR DISCLOSURE Dr Reid-Adam has disclosed no financial relationships relevant to this article. This commentary does not contain a discussion of an unapproved/investigative use of a commercial product/device.