Henoch Schonlein purpura in children: an epidemiological study among Dutch paediatricians on incidence and diagnostic criteria

Background

The aim of the present study on the occurrence of Henoch–Schönlein Purpura (HSP) in Dutch children is to give some insight into the epidemiology of HSP in the Netherlands, to record the diagnostic criteria used by Dutch paediatricians and to evaluate the accuracy of the latter using the presence of IgA in the skin when biopsies are available.

Methods

Each month in 2004, all Dutch paediatricians received an electronic card asking them to mention new diagnosed HSP. Paediatricians reporting one or more new patients with HSP were sent a list of questions concerning various parameters.

Results

232 patients from 0 to 18 years of age (6.1/10⁵) were reported as having contracted HSP in 2004. 29% presented renal symptoms. In accordance with the classification criteria of the American College of Rheumatology, 80% of paediatricians consider that isolated purpura (without haematological abnormalities) is sufficient to allow the diagnosis of HSP in children. From the 17 skin biopsies performed, only 9 (53%) presented IgA deposits. The follow‐up duration, considered as necessary, was longer in case of renal symptoms at presentation. However, 45% of patients without renal symptoms would be followed for more than 1 year.

Conclusion

Considering the recent (2006) EULAR/PReS endorsed consensus criteria for the classification of childhood vasculitides, HSP should have been diagnosed in only 160 of the 179 patients of our study. The use of isolated non‐thrombocytopenic purpura as the only criterion to diagnose HSP in children might therefore lead to over diagnosis and unnecessary follow‐up.Heberden¹ was the first to describe the association of macroscopic haematuria with a purpuric rash, colicky pain, bloody stools and arthralgia. Erythaematous or purpuric rash and joint pain was reported again by Schönlein.² Schönlein''s former pupil, Henoch,³ described 4 children with the combination of rash, colic, bloody diarrhoea and joint pain, and in a later report added haemorrhagic nephritis to the list of components of the syndrome, thus completing the modern definition of the disease. The latter has been formulated by the International Consensus Conference on Nomenclature of Systemic Vasculatides⁴ as “a vasculitis with IgA‐dominant immune deposits affecting small vessels and typically involving skin, gut, and glomeruli and associated with arthralgias or arthritis”. The role of IgA deposition in the pathophysiology of the disease was first suspected in 1968 when Urizar and co‐workers⁵ showed IgA deposits in renal biopsies of patients with Henoch–Schönlein purpura. In the same year, Berger and Hinglais,⁶ reported for the first time a form of glomerulonephritis characterised by mesangial accumulation of IgA which later led to the denomination of IgA nephropathy (IgAN). IgA deposits were also found in other types of tissues such as skin or intestine in both diseases. Henoch–Schonlein purpura nephritis (HSPN) and IgAN are considered nowadays as related diseases, since both have been described in identical twins⁷ and bear identical pathological and biological abnormalities.⁸ It has become obvious in the last 15 years that the primary process leading to IgA deposition in both IgAN and Henoch–Schonlein purpura (HSP) results from a defect in IgA1 glycosylation that impedes IgA1 clearance by the liver and provokes an accumulation of IgA1 and IgA1‐containing complexes in plasma.⁸ The denomination HSP should therefore refer nowadays to a well‐defined pathophysiological entity leading to tissue lesions induced by IgA deposition and possibly being complicated by chronic renal failure in the long term, particularly during a subsequent pregnancy, even in case of minimal renal symptoms at presentation or apparent complete recovery.^9,10 This possible evolution implies long‐term follow‐up in case of renal abnormalities and may cause anxiety for patient and family. Following the classification criteria for vasculitis of the American College of Rheumatology (ACR)¹¹ according to which the presence of palpable purpura in a patient under 16 years of age is sufficient to assess the diagnosis of HSP, paediatricians have been used to set up the diagnosis on the presence of purpura only. This criterion is also used in all epidemiological studies on HSP reported up to now. The latter have been performed in children of various countries in increasing number the last few years. They report annual incidences varying from 6.7 per 10⁵ in Saudi children¹² to 20.4 per 10⁵ children in the UK.¹³The aim of the present study on the incidence of HSP in Dutch children is not only to give some insight into the epidemiology of HSP in the Netherlands but also to record the diagnostic criteria used by Dutch paediatricians and to evaluate the accuracy of the latter using the presence of IgA in the skin when biopsies are available.