An otherwise healthy 18-month-old boy presented with palpable purpura over the legs, arms, and buttocks; his face, neck, and trunk were spared. The patient was otherwise asymptomatic, alert, and playful. His mother reported that the child had a “stuffy nose and cough” 1 month earlier.
The physical examination was unremarkable except for the distinctive rash, which led to the suspicion of Henoch-Schönlein purpura. A biopsy from one of the purpuric areas revealed superficial and deep vasculitis and a focal vascular positivity for IgA; this confirmed the clinical impression of Henoch-Schönlein purpura.
Dr Linda Castaneda of Evanston, Ill, writes that this disorder, which occurs in 10 per 100,000 children in the United States, is the most common acute leukocytoclastic vasculitis in this age group.1 The disease commonly follows an upper respiratory tract infection; other triggers may include malignancy, food, and drugs.
Henoch-Schönlein purpura appears to be an unusual immune system reaction to the trigger. Circulating IgA-containing immune complexes become trapped within the skin, blood vessel walls, GI tract, and kidneys and lead to a rash plus 1 or more of the following clinical features: arthritis, which occurs in 82% of patients; abdominal pain, in 63%; nephritis, in 40%; and GI bleeding, in 33%.2,3
The rash is distinctive because it arises primarily on dependent portions of the body. Pruritic papules, which rapidly progress to palpable purpura, occur on top of crops of pinpoint petechiae and coalescent ecchymosis. These lesions eventually fade, leaving brown macules in their place.4
The differential diagnosis includes child abuse, idiopathic thrombocytopenic purpura, thrombotic thrombocytopenic purpura, Wegener granulomatosis, and rheumatoid arthritis.
Although Henoch-Schönlein purpura is generally an acute, self-limited illness, very rarely long-term complications may occur in the joints, kidneys, and bowels. If symptoms do not resolve spontaneously, an extensive workup, perhaps including an abdominal ultrasound or CT scan, may be warranted.5