Henoch-Schönlein Purpura

by Terri Finkel, M.D.

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References ... Dedication

Henoch-Schönlein Purpura (HSP) is the most common childhood vasculitis, but its etiology remains unknown. Our group at National Jewish believes that certain strains of streptococci or staphylococci colonize patients, and produce toxins that act as superantigens to trigger the immunopathology of HSP. We are seeking specimens from suspected patients who are age 2-20 to help us test our hypothesis.

About two-thirds of HSP patients have a mild, self-limited disease that does not require hospitalization or therapy, and resolves in 3-4 weeks with no significant sequelae. However, about a third of patients have a recurrence within the first year following their initial episode.

The most devastating long-term morbidity is renal involvement. Renal insufficiency develops in about 5% of cases, which can lead to end-stage renal failure.

About 7% of patients have severe gastrointestinal involvement, including hemorrhage or intussusception. The most devastating long-term morbidity is renal involvement. Renal insufficiency develops in about 5% of cases, which can lead to end-stage renal failure.

HSP is relatively rare, with an estimated annual incidence of about 13.5 cases/100,000 children. Cases usually occur in clusters, most often during the winter, which suggests an infectious etiology. Half of all HSP patients have a preceding upper respiratory infection, often in association with a throat culture that is positive for group A b-hemolytic streptococci.

The diagnosis is usually straightforward because of the highly characteristic purpuric rash that develops on the buttocks and lower extremities; there is virtually no other disorder that mimics this rash. Rounding out the diagnostic triad is colicky abdominal pain and arthritis.

A highly characteristic purpuric rash develops on the buttocks and lower extremities; there is virtually no other disorder that mimics this rash.

We speculate that HSP develops when streptococci or Staphylococcus aureus on the pharynx, rectum, or skin of children produce pyrogenic exotoxins that mediate systemic inflammation. The exotoxins may act as superantigens, proteins that are potent stimulators of a broad spectrum of T cells and macrophages. Among the stimulated T cells may be autoimmune clones that attack the patient's tissues and cause the disease's pathology.

Our study will investigate whether bacteria grown from the skin, pharynx, or rectum of HSP patients secrete bacterial toxins that are known to act as superantigens. We plan to enroll over a two year period three groups of subjects who are between the ages of 2 and 20: 17 patients with a confirmed diagnosis of HSP based on an acute onset of palpable purpura, arthralgia/arthritis, and abdominal pain; 17 age-matched, normal, healthy control subjects; and 17 pediatric patients with systemic lupus erythematosus, who will serve as a disease control group. Patients with a prior history of HSP will not be excluded.

If this study and follow- up investigations document a role for bacteria in the etiology of Henoch-Schönlein Purpura, one practical implication will be that children diagnosed with the disease should be treated with an antibiotic.

Serum specimens, throat, rectal, and skin cultures will be collected from all participants. When clinically indicated, a skin biopsy will also be collected. Patients with a suspected diagnosis of HSP based on the diagnostic triad need not come to Denver to participate; specimens can be submitted by their primary care physician. Follow- up serum specimens and interval histories will also be obtained from the HSP patients. Patients will be compensated for their participation.

If this study and follow- up investigations document a role for bacteria in the etiology of HSP, one practical implication will be that children diagnosed with the disease should be treated with an antibiotic to help clear their superantigen-producing infection.

For more information or to contact Dr. Terri Finkel, call LungLine at 1-800-222-LUNG.

References

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1. Cassidy JT, Petty RE. 1995. Vasculitis. In: Textbook of Pediatric Rheumatology. pp.365-422. W.B.Saunders Company, Philadelphia, Pa.

2. Kotzin BL, Leung DYM, Kappler J, Marrack P. Superantigens and human disease. Adv Immunol. 1993;54:99-146.

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