IgA vasculitis (Henoch–Schönlein purpura) !

The most common vasculitis of children: a raised purple rash on the legs and buttocks, joint pain, belly pain and sometimes kidney inflammation.

Updated 2026-11-01

Structures involved

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Why it happens

What it is

A small-vessel vasculitis with IgA1-dominant immune deposits in the skin, gut, joints and kidneys. The classic tetrad is palpable purpura without low platelets, arthritis or arthralgia, abdominal pain and kidney involvement (haematuria, proteinuria). It often follows an upper respiratory infection.

Who gets it

The most common systemic vasculitis of childhood, peaking between about 3 and 10 years and slightly more common in boys, with more cases in autumn and winter after respiratory infections. Adults are affected less often but tend to have more severe kidney disease.

Causes

Immune reaction with galactose-deficient IgA1 forming immune complexes in small vessels
Preceding upper respiratory infection (often streptococcal or viral) in many children
Less often drugs, vaccines or insect bites; sometimes no trigger is found

Risk factors

Childhood (3–10 years)
Recent upper respiratory infection
Autumn and winter
Adult onset carries a higher risk of kidney disease

Pathophysiology

Abnormal IgA1 forms immune complexes that deposit in the walls of capillaries, venules and arterioles, activating complement (alternative pathway) and attracting neutrophils: a leukocytoclastic vasculitis. Leaking skin vessels produce palpable purpura; bowel wall oedema and bleeding cause colicky pain and can act as a lead point for intussusception; mesangial IgA deposits cause a glomerulonephritis identical to IgA nephropathy.

Symptoms and signs

Palpable purpura and petechiae, mainly on the legs and buttocks (gravity-dependent areas)
Arthralgia or arthritis of the knees and ankles, without lasting damage
Colicky abdominal pain, vomiting and sometimes blood in the stool
Haematuria and proteinuria; hypertension in some
Swelling of the scalp, hands, feet or scrotum, especially in young children

Diagnosis

Clinical: Mainly clinical: palpable purpura predominantly on the lower limbs plus at least one of abdominal pain, arthritis/arthralgia, renal involvement or IgA on biopsy (EULAR/PRINTO/PRES criteria).
Tests: Normal platelet count and coagulation (distinguishes it from thrombocytopenic purpura); urinalysis and blood pressure at diagnosis and during follow-up; creatinine and urine protein-to-creatinine ratio. Skin biopsy (leukocytoclastic vasculitis with IgA deposits) or kidney biopsy in atypical or severe cases.
Imaging: Abdominal ultrasound if there is severe abdominal pain, to look for intussusception or bowel wall thickening; scrotal Doppler ultrasound to exclude torsion.

Differential diagnosis

Immune thrombocytopenia and leukaemia (low platelets)
Meningococcaemia and other sepsis with purpura
Acute haemorrhagic oedema of infancy
Other vasculitides (ANCA vasculitis, hypersensitivity vasculitis) and lupus
Acute appendicitis or intussusception as primary surgical problems
Post-streptococcal glomerulonephritis and IgA nephropathy

Goal of treatment

Relieve symptoms while the disease settles on its own, detect and treat abdominal and kidney complications early, and follow the kidneys until urinalysis is normal.

Treatment

Conservative: Supportive care in most children: rest, hydration and leg elevation; most can be managed at home.
Medical: Pain relief with paracetamol or NSAIDs (avoid NSAIDs with kidney involvement or GI bleeding); glucocorticoids for severe abdominal pain or other severe organ involvement.
Medical: Significant nephritis (heavy proteinuria, reduced kidney function or crescents) is treated with glucocorticoids and other immunosuppressants, plus ACE inhibitors or ARBs for proteinuria, under nephrology care.
Follow-up: Repeated urinalysis and blood pressure checks for at least 6 months after the episode; nursing monitoring of abdominal pain, stools, fluid balance and urine.

Complications

Intussusception (usually ileo-ileal), bowel ischaemia or perforation
IgA vasculitis nephritis, sometimes progressing to chronic kidney disease
Hypertension
Recurrence of the rash in the following months
Pregnancy complications (hypertension, proteinuria) in women with past kidney involvement

Prognosis

In most children it resolves within about a month, although a third may have a recurrence. Long-term outlook depends on the kidneys: most nephritis resolves, but a minority develop chronic kidney disease, more often adults.

Test yourself

Think of the answer, then tap the question to see it.

What is the classic tetrad of IgA vasculitis?

Palpable purpura (with normal platelets), arthralgia/arthritis, abdominal pain and renal involvement.

What is the platelet count in IgA vasculitis, and why does it matter?

Normal; purpura with normal platelets points to vasculitis rather than thrombocytopenia.

Which GI complication must be watched for in a child with IgA vasculitis?

Intussusception, usually ileo-ileal.

Which kidney disease shares the same histology?

IgA nephropathy (mesangial IgA deposits).

What follow-up is needed after an episode?

Serial urinalysis and blood pressure checks for at least 6 months to detect nephritis.

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Educational information, not medical advice. For any symptom, see a health professional.

Sources: IgA vasculitis - Henoch-Schonlein purpura (MedlinePlus (U.S. National Library of Medicine), 2025).

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Representative model, for educational purposes only.

Skin highlighted on the Durgical 3D model