Henoch–Schönlein purpura

Published on 23/06/2015 by admin

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Last modified 23/06/2015

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16.7 Henoch–Schönlein purpura

1 There is no diagnostic laboratory test for the diagnosis of Henoch-Schönlein purpura.

2 The diagnosis is clinical and consists of the tetrad: palpable purpura in patients with neither thrombocytopenia or coagulopathy, arthritis/arthralgia, abdominal pain and renal disease.

3 Urinalysis, and blood pressure should be measured at presentation.

4 Clinical hallmark of Henoch–Schönlein nephritis is haematuria.

5 Onset of nephritis may be delayed for weeks or months after onset of other symptoms.

6 All patients with Henoch–Schönlein nephritis need follow up for 6 months even if urinalysis is normal at presentation.

7 There is no need for follow up beyond the first 6 months if urinalysis remains normal.

8 Recurrence of Henoch–Schönlein purpura is common and is normally observed within 4 months of resolution of original symptoms.

Introduction

Henoch–Schönlein purpura (HSP) is the most common acute vasculitis affecting children. It has a prominent cutaneous component. It is a leukocytoclastic vasculitis that affects small vessels (arterioles and venules). The aetiology is unknown. The disease is more common in males, with mean age of occurrence 4–7 years. Infants tend to have milder disease and those less than 2 years of age are less likely to have nephritis and abdominal pain in comparison with older children. With the exception of nephritis, it is generally an acute self-limited illness lasting from several days to several weeks.

The characteristic histological finding on skin biopsy is neutrophil infiltration in and around dermal vessels. Histological changes in the kidney range from minimal change to focal or diffuse mesangial proliferation that may be accompanied by glomerular crescent formation. The characteristic finding on immunofluorescence is diffuse mesangial deposition of immunoglobulin A (IgA) and complement 3 (C3). IgA plays a central role in the pathogenesis of HSP.

The reported incidence of nephritis is 20-50% but may in fact be higher. Renal involvement may manifest with haematuria ± proteinuria and occasionally with nephritic or nephrotic syndrome or with renal failure associated with rapidly progressive glomerulonephritis. Risk factors for renal progression are nephrosis, hypertension, renal impairment at presentation, and haematuria.

History

There is usually a history of antecedent upper respiratory tract infection. The characteristic rash is the most frequent presentation. Arthritis is the second most frequent manifestation, occurring in approximately 80% and though it may be incapacitating, it is self-limiting and non-deforming. Gastrointestinal involvement occurs in 50–75% of patients and is potentially the most serious complication of HSP due to the possible development of gastrointestinal bleeding and intussusception.

The clinical hallmark of HSP nephritis is haematuria. In contrast to arthritis and abdominal pain, it is extremely uncommon for nephritis to precede the appearance of the rash. The onset of nephritis may in fact be delayed for weeks or months after the onset of other symptoms. Approximately 80% of patients manifest nephritis within 4 weeks and 95% within 3 months of the onset of other symptoms.

Examination

The clinical features of HSP may be atypical in the extremes of age. The clinical manifestations can develop over days or weeks. The characteristic rash consists of crops of palpable purpura and is symmetric in distribution and located on the extensor surfaces of the arms, legs and buttocks. It is worth noting that the rash is not restricted to these areas. The rash may begin with urticaria that progresses over 24 hours to palpable purpura. The arthritis involves the knees, ankles or feet and may result in refusal to weight bear. Periarticular swelling and tenderness are often noted.

Gastrointestinal symptoms of nausea, vomiting and abdominal pain occur in approximately 50%. These symptoms are caused by submucosal haemorrhage and oedema. Asymptomatic microscopic haematuria occurs in most but up to 40% have gross haematuria. Proteinuria occurs in conjunction with haematuria in two-thirds of patients but the occurrence of proteinuria alone is rare.

Investigations

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