This palpable, nontender, nonblanching rash had developed on the elbows of an 18-year-old boy and spread to the ankles and feet. The rash was accompanied by moderate abdominal pain associated with episodes of nonbloody emesis that did not change with eating or bowel movements. Diffuse joint pain developed the day after the rash appeared.
He had no cough, hemoptysis, fever, chills, hematuria, or diarrhea. He denied recent travel and illicit drug use. A week earlier, he was evaluated by his primary care physician, who diagnosed Rocky Mountain spotted fever and prescribed an antibiotic. However, his symptoms persisted despite treatment.
Vital signs were stable.
There was mild, diffuse pain on palpation of the abdomen. Results of blood tests, urinalysis, and a chemistry panel were all normal. Henoch-Schönlein purpura (HSP) was diagnosed on the basis of the classic clinical presentation of rash, polyarthralgia, and abdominal pain. The American College of Rheumatology criteria include palpable purpura, age of onset before 20 years, bowel angina, and wall granulocytes on biopsy; the presence of 2 or more criteria yields a sensitivity of 87% and a specificity of 88%.1 While a biopsy to verify the diagnosis is desirable, in the clear absence of signs and symptoms suggestive of other entities, the diagnosis of classic HSP can be made on clinical grounds in the proper demographic context.
HSP is the most common systemic vasculitis in children, with an incidence of about 14 cases per 100,000; males are affected twice as often as females.2 Most cases occur before age 10 years.3 In addition to Rocky Mountain spotted fever, the differential diagnosis includes idiopathic thrombocytopenic purpura, poststreptococcal glomerulonephritis, and Wegener granulomatosis.
The long-term prognosis is good in most cases.
About 80% of patients recover within 2 weeks, although nearly 35% of patients have one or more recurrences.4 HSP progresses to end-stage renal failure in only 1% to 5% of affected children.5 This patient responded well to supportive therapy, including fluid hydration, pain control, and antiemetic medications. After several follow- up visits with his primary care physician and a nephrologist, he was noted to have recovered fully.
