IgA vasculitis

IgA vasculitis (formerly known as Henoch-Schonlein purpura (HSP)) is a type of non-thrombocytopenic immune-mediated small vessel acute leukocytoclastic vasculitis.

It tends to occur in the pediatric population (peak incidence 3-10 years) ³.

In order to differentiate from other types of vasculitides, the four commonly adopted diagnostic criteria by the American College of Rheumatology are:

• age of onset less than 20 years (although some case series show disease involvement in older individuals)
• palpable skin purpura
• gastrointestinal bleeding
• intussusception, typically ileoileal
• biopsy showing granulocytes around small arteriolar/venular walls.

Pathology

There is deposition of IgA immune complexes in small vessels.

Distribution

Commonest organ systems which get 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.

Prognosis

The disease is self-limiting in most instances.

Complications

Gastrointestinal tract

• small bowel intussusception
• small bowel obstruction
• small bowel infarction: 3-5% ³
• bowel perforation

Renal

• renal failure

History and etymology

It is named after Eduard Heinrich Henoch, German pediatrician (1820-1910) ⁸ and Johann Lukas Schönlein, German physician (1793-1864).

Differential diagnosis

On a CT/contrast study for the bowel consider:

• inflammatory bowel disease (e.g. Crohn disease)
• small bowel lymphoma
• ischemic colitis