Henoch-Schönlein purpura

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}} In medicine(rheumatologyand pediatrics) Henoch-Schönlein purpura (HSP, also known as allergic purpura) is a form of vasculitisthat mainly affects children. Its course is generally benign, although some serious complications can develop, mainly of the kidneyand intestine.

Signs and symptoms

The purpura that are mentioned in the name of the disease are present in all patients. They are located on the legs and arms, and progress to the trunk. As purpura are small haemorrhages, they are non-blanching (i.e. they do not disappear on pressure), which can lead to confusion with the petechiaeof meningococcal sepsis. Often, the symptoms are preceded by a viralupper respiratory tract infection.

Other symptoms are: arthritis(75%, non-erosive, often present before all other symptoms), abdominal pain(65%), intestinal bleeding (35%), nephritisand hematuria(40%) and proteinuria (25%). Many other symptoms have been reported, but their specificity for HSP is limited.

33% will develop recurrence of the syndrome. 1% will progress to chronic renal failure. Both recurrence and renal complications are more frequent in older children and adults.

Some patients can present with intussusception; this complication is the folding of a segment of the intestineinto its own lumen, leading to hematocheziaand severe abdominal pain. It requires urgent surgery, before the intestinal tissue becomes necroticand dies.

Diagnosis

There is no definitive test for HSP, but blood testsare commonly performed. These include: full blood count, electrolytes, renal function, C-reactive proteinand erythrocyte sedimentation rate. Immunoglobulinlevels show elevated IgA in 50% of the cases. Complementlevels are normal (in other vasculitis syndromes these can be consumed and therefore low).

Rarely, a renal biopsyhas to be performed to arrive at a full diagnosis. This shows mesangialproliferation and is indistinguishable from IgA nephritis.

Pathophysiology

HSP is a form of vasculitis that is mediated by antibodies of the subclass IgA₁. These are found in the cutaneous lesions, as well as other inflammatory patches in the kidney (mesangium) and the intestine. IgA nephritis has many parallel symptoms, and is also often preceded by an infection, raising the suspicion that the nephritis may be a form of HSP limited to the kidney.

HSP can develop after infections with streptococci(Group A, β-haemolytic), hepatitis B, herpes simplex virus, parvovirus B19, Coxsackievirus, adenovirusand Helicobacter pylori. Certain medications have been reported to cause HSP as an idiosyncratic reaction.

In the 1990s, it was discovered that an abnormality of the IgA₁ may be the causative factor of this disease. IgA₁ and IgD differ from the other classes of antibody through an 18 amino acid-long hinge region between complement-fixating region 1 and 2. Of the amino acids, half is proline, while the other ones are mainly serineand threonine. The majority of the serines and the threonines have elaborate sugar chains, connected through oxygenatoms (O-glycosylation). This process is thought to stabilise the IgA molecule and make it less prone to proteolysis. The first sugar is always N-acetyl-galactosamine(GalNAc), followed by other galactosesand sialic acid.

In HSP and IgA nephritis, it appears that these sugar chains are deficient. The cause for this abnormalty is thought to be viralneuraminidase, which removes sialic acid. This abnormality leads to polymerisation of IgA₁, mainly in the renal mesangium. While the local mechanism that leads to the vasculitis is not completely understood, recent findings seem to confirm this theory.

Treatment

Many cases are self-limiting and don't require any therapeutic intervention. Steroidssuppress the joint pain and the abdominal pain, but do not affect the progression of the purpura. The prognosis depends mainly on the seriousness of the renal involvement: hematuria, nephrotic syndrome, decreased renal function and hypertensionpredict future development of chronic renal failure.

As most patients are children, a renal biopsyis only performed when there are concerns about long-term renal prognosis. If over 50% of the glomerulishow crescenteric changes, more aggressive treatment may be required.

Second-line therapy consists of methylprednisolonepulse therapy. Other therapies, most of which have not been compared systematically, are DMARDs(disease-modifying antirheumatic drugs, e.g. azathioprineor methotrexate), cyclophosphamideor plasmapheresis.

Epidemiology

The incidence of HSP is about 1:7,000 in the United States. The medianage is 6 years at disease onset, and 90% is under 10 years old. Nevertheless, it has been described in adults. Boys tend to be more often affected than girls.

History

The disease carries the name of Eduard Heinrich Henoch (1820-1910), a German pediatrician, and his teacher Johann Lukas Schönlein (1793-1864), who described it in the 1860s.

The English physicianWilliam Heberden(1710-1801) and the dermatologistRobert Willan (1757-1812) had already described the disease in 1802and 1808, respectively, but the name Heberden-Willan disease has fallen in disuse. William Oslerwould be the first to see HSP as a form of allergy.

Source

• Saulsbury FT. Henoch-Schönlein purpura. Curr Opin Rheumatol 2001;13:35-40. PMID 11148713.

See also

• Anaphylactoid purpura

External links

• Whonamedit.compage on HSPde:Purpura Schönlein-Henoch

fr:Purpura rhumatoïde sv:Henoch-Schönleins purpura

This article is licensed under the GNU Free Documentation License.
It uses material from the http://en.wikipedia.org/wiki/Henoch-Sch%C3%B6nlein+purpura Wikipedia article Henoch-Schönlein purpura.