Henoch‐Schönlein Purpura (HSP) is a primary small vessel vasculitis. This immunologically mediated vasculitis involves various organ systems including skin, kidney, muscle, joints, gut and brain. Clinical manifestations include purpuric skin lesions, abdominal pain, gastrointestinal bleeding, arthropathy and renal involvement (Saulsbury 1999). HSP was first describing by William Heberden 200 years ago. Subsequently Schönlein described "Peliosis rheumatica" in patients who had arthralgia and purpura. In 1874 Eduard Henoch, Schönlein's former student, reported gastrointestinal involvement and also recognised that haemorrhagic nephritis may be a serious complication in this syndrome (Fervenza 2003). The international Consensus Conference on Nomenclature of Systemic Vasculitides has characterised this syndrome as " a vasculitis with IgA dominant immune deposits affecting small vessels and typically involving skin, gut, and glomeruli and associated with arthralgias and arthritis" (Jennette 1994). The criteria for diagnosing HSP proposed by The American Collage of Rheumatology included: palpable purpura, age less than 20 years old at onset, bowel angina and gut wall granulocytes on biopsy (Mills 1990). Although HSP can be found both in children and adults, it is the most common systemic vasculitis in children (Fervenza 2003). The annual incidence of HSP in children varies between 13.5 and 20/100,000 (Neilson 1998; Niaudet 1993; Steward 1988). The incidence is highest in children aged 4‐6 years (70.3/100,000 children) (Gardner‐ Medwin 2002).

Glomerulonephritis is one of the major complications of HSP. In a series of patients referred to renal units the incidence of kidney involvement in HSP was about 50% (Haycock 1992; Saulsbury 1999). However the incidence of kidney involvement in HSP from an unselected series of patients presenting to emergency or to a general medical clinic is found only 20% (Steward 1988). Clinically renal involvement is manifested by microscopic or macroscopic haematuria, proteinuria, nephrotic syndrome and reduced renal function. Among children with HSP and renal involvement nephritis occurs in 40% of patients; 83% had microscopic hematuria alone,17% had macroscopic hematuria, 63 % had hematuria and proteinuria, 3% had nephrotic syndrome (Saulsbury 1999). Eighty percent of patients, who develop renal involvement, do so within four weeks of the onset of HSP and 95% develop renal involvement within three months. Hypertension was found to be 61% in one series of patients (Scharer 1999). It is rare for renal involvement to precede other manifestations of HSP (Haycock 1992 ).

In general, the prognosis for long‐term renal function in HSP is excellent in children with microscopic or macroscopic haematuria alone. However patients with nephrotic syndrome and reduced renal function frequently show a progressive course to end‐stage renal failure (ESRF). In one study, 47% of patients with acute nephritic syndrome (haematuria, hypertension, reduced renal function), nephrotic syndrome or combined nephritic‐nephrotic syndrome at presentation continued to have active renal disease (proteinuria > 1 g/m²/d) or progressed to ESRF over 6.1 ± 4.9 years of follow‐up (median 4.3, range 1 to 22.8 years). In contrast none of the patients, who presented with low grade proteinuria (proteinuria < 1 g/m²/d) or haematuria progressed to chronic renal failure (CRF) or end‐stage renal disease (ESRD). In this study 45% of patients with crescentic glomerulonephritis at initial renal biopsy had active nephropathy (proteinuria > 1 g/m²/d with or without hypertension) at the last observation 22.8years after presentation. In contrast 87.5% of those who had only minimal glomerular alteration or mesangial proliferation at the initial biopsy, were in clinical remission or had only minor urine abnormalities at follow‐up (proteinuria (0.15 to 1.0 g/d with or without haematuria, no hypertension and normal serum creatinine) (Goldstein 1992).

Few studies have considered whether interventions in children with HSP, who are at risk of renal involvement, can prevent development of renal involvement or reduce its severity. In general treatment has been aimed at preventing progression to CRF and ESRD in patients with acute nephritis, nephrotic syndrome or reduced renal function. Corticosteroid therapy, azathioprine, cyclophosphamide, antiplatelet therapy, anticoagulants and plasmapheresis have been used in such patients (Bergstein 1998; Foster 2000; Kaku 1998; Iijima 1998; Niaudet 1998; Ronkainen 2003). In a multivariate analysis of prognostic factors, corticosteroid therapy was associated with a hazard ratio of 0.36 and was considered to decrease the risk of developing renal involvement (Kaku 1998). Non randomised studies have reported that corticosteroid therapy with cyclophosphamide reduces proteinuria (Flynn 2001; Tanaka 2003). In a randomised controlled trial (RCT) of early prednisolone therapy at diagnosis of HSP, there was no evidence that treatment reduced the risk of serious renal disease (Huber 2004). Although multiple treatment modalities has been used for treat glomerulonephritis in HSP, there is no consensus on the efficacy of various therapies. The aims of this study are to determine the benefits and harms of different treatment modalities used to treat established renal involvement in HSP or to prevent or ameliorate renal involvement in HSP.