IgA vasculitis (formerly known as Henoch-Schönlein purpura (HSP)) is a type of non-thrombocytopenic immune-mediated small vessel acute leukocytoclastic vasculitis.
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Epidemiology
IgA vasculitis tends to occur in the pediatric population (peak incidence 3-10 years) 3. It is the most common type of vasculitis in children 10.
Diagnosis
The diagnosis of IgA vasculitis is based on a combination of typical clinical and pathological features.
Diagnostic criteria
In order to differentiate from other types of vasculitides, the 1990 diagnostic criteria by the American College of Rheumatology require two or more of 13,14:
- age of onset less than 20 years (although some case series show disease involvement in older individuals)
- palpable skin purpura
- acute abdominal pain
- biopsy showing granulocytes around small arteriolar/venular walls
The presence of two or more of these criteria has a sensitivity and specificity of 87% for IgA vasculitis 14.
Clinical presentation
IgA vasculitis tends to present as:
- a palpable, purpuric rash primarily of the extremities
- acute abdominal pain, ileoileal intussusception may be present
- arthralgia
Pathology
In IgA vasculitis, there is deposition of IgA immune complexes in small vessels.
Distribution
In IgA vasculitis, the commonest organ systems to be involved are:
- skin: 95-100%, usually the first organ to get involved
- gastrointestinal tract: 50-75%
- joints: ~80% 6
- kidneys
Rare sites:
- central nervous system 5,7
Radiographic features
Gastrointestinal tract
Plain radiograph
May show evidence of bowel wall thickening due to hemorrhage and/or evidence of bowel obstruction. Plain film features are however non-specific.
Fluoroscopy
Small bowel follow-through may show evidence of separation of bowel loops, "thumbprinting" and/or mucosal thickening.
CT
May show multifocal bowel thickening, lymphadenopathy, mesenteric edema and vascular engorgement. Although non-specific, CT findings may aid in the diagnosis of IgA vasculitis in a young patient with acute gastrointestinal illness along with other, e.g. cutaneous features of IgA vasculitis. Intussusception, typically ileoileal type, is also seen.
Ultrasound
Echogenic kidneys, target or doughnut sign in case of intussusception. IgA vasculitis has also been shown to cause massive scrotal edema and can be a source of severe pain in young boys 9.
Treatment and prognosis
The disease is self-limiting in most instances. Treatment is usually supportive including fluids and pain relief in the pediatric population. Steroids are used in adults due to the risk of serious renal involvement 10.
Complications
Gastrointestinal tract
- small bowel intussusception
- small bowel obstruction
- small bowel infarction: 3-5% 3
- bowel perforation
Renal
History and etymology
Henoch-Schönlein purpura was named after Eduard Heinrich Henoch, German pediatrician (1820-1910), and Johann Lukas Schönlein, German physician (1793-1864) 11, whom Henoch was the protégé of. Although neither was the first to describe this condition 11,12.
Differential diagnosis
On a CT/contrast study for the bowel consider:
