Henoch Scholein Purpura Flashcards
What is the epidemiology of Henoch-Schonlein Purpura
HSP can affect all age groups but most commonly children between 2 and 6 years of age. The incidence in children is reported as between 10.5 and 20.4/100,000 children per year. The latter is from a comprehensive study in the UK with information collected from primary and secondary care. The incidence was highest in the 4–6-year age group, with up to 70.3/100,000 per annum. There is a slight male preponderance of 1.2:1, with a lower incidence in black children compared with white or Asian.
What is the etiolgy of Henoch-Schonlein Purpura?
The pathogenesis of HSP is not yet clearly understood, although it is known to be an immune complex-mediated disease. Preceding upper respiratory tract infections are common particularly with group A β-haemolytic streptococcus, but many other organisms have been implicated such as mycoplasma, adenovirus, parvovirus B19, varicella and herpes simplex.
It is possible that there is a genetic predisposition to developing HSP and subsequent renal involvement. Multiple factors have been implicated including human leucocyte antigen class II genes, genetic polymorphisms of the renin angiotensin system and cytokines such as IL-1 β. HSP is also more common in children with familial Mediterranean fever.
However, any predisposition to HSP is most likely to be a combination of factors, which influence susceptibility, likelihood of renal involvement and eventual outcome.
What are the diagnostic criteria for HSP?
Diagnosis of HSP (EULAR/PReS consensus criteria)
Palpable purpura (essential) in the presence of one of the following:
1. Diffuse abdominal pain
2. Any biopsy showing predominant IgA
3. Acute arthritis/arthralgia
4. Renal involvement defined as any haematuria or
proteinuria.
What are the pathological findings of HSP?
In the skin, a biopsy of the purpura (but also of the non- affected areas) reveals IgA deposition. In the kidney, the histological findings are similar to that of IgA nephropathy. Primarily, there is mesangial proliferation with hypercellularity. There may be focal necrosis and segmental capillary collapse. Epithelial crescent formation represents more significant inflammatory damage. Histological changes are graded in a classification by the International Study for Kidney Disease in Children.
