Alteration of the complement system in children with Henoch Schönlein purpura

Advances in our understanding of the pathogenesis of Henoch-Schönlein purpura and the implications for improving its diagnosis

Henoch-Schönlein purpura (HSP) is a leukocytoclastic vasculitis classically characterized by palpable purpura, arthritis, abdominal pain and renal disease. In this article, we summarize our current understanding of the pathogenesis of HSP and the implications for improving its diagnosis. Although the pathogenesis of HSP is not fully understood yet, exciting new information has emerged in recent years, leading to a better understanding of its pathogenesis. Here, we discuss genetic predisposition, immunoglobulins with a particular emphasis on IgA1, activated complements, cytokines and chemokines, abnormal coagulation and autoantibodies in the underlying pathogenic mechanisms. Finally, diagnostic criteria for HSP developed by institutions such as the American College of Rheumatology and the European League against Rheumatism/Paediatric Rheumatology European Society were proposed to improve early detection and diagnosis.

Schönlein-henoch purpura in children and adults: diagnosis, pathophysiology and management

Schönlein-Henoch syndrome is a form of systemic small-vessel vasculitis, characterised by vascular and/or mesangial immunoglobulin A1 deposits. The main clinical manifestations are vascular purpura, predominating on the lower limbs, and articular, gastrointestinal and renal symptoms. Pulmonary, cardiac, genital and neurological symptoms have also be observed. The syndrome usually affects children, whereas it is rare in adults. The frequency of renal involvement varies between individual studies (from 20 to 100%). Renal manifestations are usually mild and transient, although chronic nephropathies may occur. Overall, an estimated 2% of children with Schönlein-Henoch purpura progress to renal failure and up to 20% of children with nephritis treated in specialised centres require haemodialysis. The renal prognosis appears to be worse in adults. Aetiological investigations are required, as a triggering factor is found in approximately half the patients (e.g. viral, bacterial and parasitic infections, drugs, toxins, systemic diseases and cancer). Dapsone has beneficial effects on cutaneous, gastrointestinal and articular manifestations in adults, especially those with chronic forms. Corticosteroids may be useful for refractory abdominal pain. Methylprednisolone pulse therapy, immunosuppressive drugs (e.g. cyclophosphamide and azathioprine), plasma exchange and polyclonal immunoglobulin therapy are beneficial in very rare life-threatening forms of the disease and in rare instances where renal function is compromised.

Henoch-Schönlein purpura in children. Report of 100 patients and review of the literature

Henoch-Schönlein purpura (HSP) is an acute leukocytoclastic vasculitis that primarily affects children. In the current report, the author presents the clinical features of 100 children with HSP and reviews the literature, placing particular emphasis on new information concerning the etiology, immunopathogenesis, and treatment of HSP. The dominant clinical features of HSP are cutaneous purpura (100%), arthritis (82%), abdominal pain (63%), gastrointestinal bleeding (33%), and nephritis (40%). The etiology of HSP remains unknown, but it is clear that IgA plays a critical role in the immunopathogenesis of HSP, as evidenced by increased serum IgA concentrations, IgA-containing circulating immune complexes, and IgA deposition in vessel walls and renal mesangium. There are 2 subclasses of IgA, but HSP is associated with abnormalities involving IgA1 exclusively, and not IgA2. This finding may be a consequence of abnormal glycosylation of O-linked oligosaccharides unique to the hinge region of IgA1 molecules. Although several lines of evidence suggest a genetic susceptibility to HSP, the fundamental basis for the abnormalities involving IgA remain unclear. In general, HSP is an acute, self-limited illness, but one-third of patients will have 1 or more recurrences of symptoms. Corticosteroid therapy may hasten the resolution of arthritis and abdominal pain, but does not prevent recurrences. To date, no form of therapy has been shown to shorten appreciably the duration of HSP. The long-term prognosis of HSP is directly dependent on the severity of renal involvement. Corticosteroids in usual doses have no effect on established nephritis. Evidence is emerging that treatment with high-dose intravenous pulse methylprednisolone coupled with azathioprine or cyclophosphamide may be beneficial in patients with severe nephritis.

Immunoglobulin and complement studies in children with Schönlein-Henoch Syndrome and other vasculitic diseases

In 35 children with Schönlein-Henoch Syndrome (SHS) serum IgG, IgM, and IgA concentrations were increased in 15%, 21%, and 44% of cases, respectively. Seven children with other vasculitic syndromes (VS) had normal serum Ig concentrations. Serum concentration of IgG subclass IgG1 was increased in 72% of children with SHS and 57% with VS. In SHS this was related to the presence of arthritis, but inversely related to nephritic symptoms. Only a few children had IgG subclasses IgG2, IgG3, or IgG4 concentrations outside the normal ranges. Platelet associated Ig (PAIg) was found in 75% of children with SHS or VS. In SHS the identification of increased amounts of PAIgG was related to the presence of nephritis. The serum concentration of properdin, a component of the alternative complement system, was reduced in 21% of children with SHS. This was related to the presence of abdominal symptoms or nephritis. No cases of retinal vasculitis was observed, but 4 of 22 children with SHS had punctuate retinal haemorrhages. SHS and VS may be clinical variations of the same syndrome. The immunological aspects indicate a close relationship with autoimmune diseases.

The rheumatic poison: a survey of some published investigations of the immunopathogenesis of Henoch-Schönlein purpura

Laboratory studies of the pathophysiology of Henoch-Schönlein purpura (HSP) have become more numerous in recent years with the recognition of the disease's links with the mucosal immune system in general and IgA nephropathy in particular. There are weak genetic associations with C4 null phenotypes and with HLA B35 and DR4. Studies of plasma proteins in HSP patients show an increased IgA concentration, activation of the alternative pathway of complement and consumption of factor XIII. High molecular weight (polymeric) IgA has been detected in affected individuals, which some investigators have called "immune complexes". Many patients synthesise an IgA rheumatoid factor in the acute phase, but other autoantibodies are largely absent. In vitro studies of lymphocytes from HSP patients have demonstrated an increased number of IgA-bearing and secreting B-cells, with altered T-cell regulation of antibody synthesis. While these observations point to immune dysregulation--primarily of IgA production--as a consistent feature of acute HSP, there is as yet insufficient information available to allow a consistent theory of pathogenesis to be formulated.

Lack of association between the HLA-A10 (A25), B18 and C2o haplotype and anaphylactoid purpura (AP)

In 41 patients with AP and 134 healthy relatives HLA haplotypes and total hemolytic complement and C2 concentrations were determined. Though complement levels were found in the lower normal range in none of the individuals studied, a genetically determined C2 deficient state could be established. No association between low C2 levels and the HLA haplotype A10(A25), B18 or an isolated A25 or B18 was observed. A comparison of phenotype frequencies of AP patients with controls showed no significant difference. Contingency table analysis of patients and control haplotypes showed a definite close association with HLA-A1, Bw22, A2, Bw16, and A29, B12.