Diagnosis of Henoch-Schönlein purpura: renal or skin biopsy?

Henoch-Schönlein purpura (HSP) is a form of systemic vasculitis characterized by vascular wall deposits of predominantly IgA, typically involving small vessels in skin, gut, and glomeruli and associated with purpura, intestinal colic, hematuria, and arthralgia or arthritis. HSP nephritis leads to chronic renal failure in up to 20% of pediatric patients after 20 years of follow-up in selected series. The risk is related to the initial clinical presentation and is maximal (more than 50%) when initial signs are a combination of nephrotic and nephritic syndromes. Although less important, the risk persists for mild renal symptoms or when the patient has apparently completely recovered from the renal disease. Other types of non-IgA-related leukocytoclastic vasculitis may be difficult to discriminate from HSP, thus confounding the diagnosis. The clinical picture of HSP is often incomplete and renal signs can become manifest years after initial signs. When based on clinical signs only, the diagnosis of HSP can therefore be missed, and some patients risk developing silent chronic renal failure after decades without appropriate treatment. Patients can also be overdiagnosed as HSP and thus submitted to unnecessary follow-up. It is therefore important that HSP should be correctly diagnosed from the initial signs. As the finding of IgA deposits in vessel walls associated with the characteristic signs of small-vessel vasculitis is a sine qua non in the diagnosis, a skin biopsy should be performed for histological and immunofluorescence studies in cases of clinical suspicion of HSP. The systematic diagnostic use of a cutaneous biopsy should not only improve the follow-up of patients with HSP but will also allow a reliable epidemiological study of vasculitis in children and a better knowledge of the disease.