ReviewThe diagnosis and classification of Henoch–Schönlein purpura: An updated review☆
Introduction
Henoch–Schönlein purpura (HSP) is a systemic small vessel vasculitis that occurs commonly in children. The annual incidence is 13–20 per 100,000 children under 17 years old [1], [2]. It is characterized by non-thrombocytopenic palpable purpura that mostly located on the dependent parts like lower extremities and buttocks, arthralgia/arthritis, bowel angina, and hematuria/proteinuria. Treatment is supportive because the disease course is usually benign and self-limited [3]. Progressive impairment of renal function, bowel perforation, and central nerve system involvement is rare but major morbidity of HSP [4], [5], [6]. Aggressive therapies with steroid and/or immunosuppressants are then indicated under such conditions.
Although this disease is not uncommon in children, the etiology and pathogenesis are still yet to be determined. Previous epidemiological studies have found striking seasonal variations in HSP, with most cases occurring in the autumn and winter. HSP has also been associated with a history of preceding infections, especially upper respiratory tract infection [1], [3], [7]. In addition, other characteristics of HSP include the deposition of IgA and C3 in small vessel walls, polymorphonuclear neutrophil infiltration around the vessel and in vessel walls, and increased serum levels of IgA and proinflammatory cytokines at the acute stage [3], [8]. Combined, HSP is regarded as a specific immune-mediated entity induced by environmental factors, particularly infections.
Clinically, since there are no disease-specific laboratory abnormalities, HSP is currently diagnosed based on symptoms and signs and histopathological findings [3], [9]. In this article, we reviewed and compared various diagnostic criteria of HSP. In addition, differential diagnosis of HSP and some potential biomarker that may assist in diagnosing HSP were also reviewed.
Section snippets
Diagnostic criteria of HSP
Schönlein first described HSP as triad of purpuric rash, arthritis, and abnormalities of the urinary sediment in 1837 [10]. In 1874, Henoch described the association of purpuric rash, abdominal pain with bloody diarrhea, and proteinuria [11]. Up to date, several sets of diagnostic criteria for HSP have been proposed; the detail and comparison of these different classification criteria were further reviewed and discussed as follows.
Differential diagnosis of HSP
HSP must be distinguished from other diseases with similar presentations (Table 2). Thrombocytopenic purpura like immune thrombocytopenic purpura can be easily identified by the detection of low platelet count. If it is difficult to decide the cause of cutaneous purpuric lesions that may be presented in other types of vasculitis such as urticarial vasculitis, cryoglobulinemia, and HV, a skin biopsy and immunofluorescence study may assist in the diagnosis [3], [16], [17], [20]. Some rheumatic
Biomarkers for HSP diagnosis
In HSP, the platelet count is normal or increased. A moderate leukocytosis with a left shift is noted in some patients. Antinuclear antibody is mostly undetectable, and serum levels of C3 and C4 are usually within normal limit [3]. Although some proinflammatory cytokines and chemokines are elevated at acute stage [8], [26], these laboratory abnormalities are not specific for HSP but can be seen in a variety of inflammatory conditions. The presence of LCV and IgA-immune deposits on skin and/or
Conclusion
The current diagnostic criteria have high sensitivity and specificity; most HSP patients are accurately diagnosed based on them. However, some patients have atypical presentations and biopsies are sometimes not easily obtained. Therefore, the development of less invasive laboratory tests that are of diagnostic value is needed. Clearly, the elucidation of HSP pathogenesis becomes important that may identify some disease-specific biomarkers assisting in HSP diagnosis.
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Financial support: This work was partly supported by a grant from the National Science Council, Taiwan (grant number: NSC 100-2314-B-002-095-MY3).