IgA vasculitis (Henoch-Schonlein purpura)

HSP · Henoch-Schonlein purpura · IgA vasculitis · IgAV · anaphylactoid purpura

The commonest childhood vasculitis - the rash settles by itself, but the kidney needs following for months.

GPBand B

Red flags

Severe abdominal pain, bilious vomiting or blood in the stool - intussusception is a recognised complication and needs imaging
Hypertension, oedema, or visible haematuria - nephritis, the complication that determines long-term outcome
Scrotal pain or swelling - testicular torsion is a differential, not something to attribute to the vasculitis
An unwell, febrile or toxic-looking child - reconsider meningococcal disease and treat accordingly
Purpura in an infant, or an atypical distribution - IgA vasculitis is unusual in the very young, and both should lower your threshold for specialist review. No age cut-off is given here: the SHARE recommendations this entry cites do not set one

Recognise

On light skin

Crops of raised, palpable purple-red purpura on the buttocks and backs of the legs, appearing in waves, sometimes preceded by an urticarial or maculopapular stage.

On brown and black skin

Purpura reads as darker brown, violaceous or almost black against brown and black skin rather than purple-red, and the early urticarial phase may not look red at all. This is one of the conditions where palpation matters more than inspection: IgA vasculitis purpura is raised and can be felt with a fingertip, and that texture is entirely independent of skin tone. Run your fingers over the buttocks and extensor legs. Resolution leaves post-inflammatory hyperpigmentation that can persist for months and is often mistaken by families for continuing disease.

In any skin tone

Palpable purpura - you can feel it, which separates it from a flat petechial rash
Distribution is the diagnosis: buttocks and extensor legs, sparing the trunk
Joint pain or swelling, typically knees and ankles, in the majority
Colicky abdominal pain - and this can precede the rash, which is how the diagnosis gets missed
The child is usually not systemically toxic, unlike meningococcal disease
Often follows an upper respiratory infection

Distribution

Symmetrical palpable purpura over the buttocks and extensor surfaces of the legs, sometimes the arms. Characteristically spares the trunk. In infants the face and ears may be involved.

Photographs

Palpable purpura on the lower leg in IgA vasculitis. Crops of raised purple-red papules and plaques, many confluent. The word that matters i — Palpable purpura on the lower leg in IgA vasculitis. Crops of raised purple-red papules and plaques, many confluent. **The word that matters is palpable** - these lesions can be felt as well as seen, which separates vasculitic purpura from the flat purpura of a clotting problem. On brown and black skin the colour reads as a dark brown or slate bruise-like change rather than purple, so palpate the buttocks and the backs of the legs rather than relying on the look.
Fitzpatrick II (Fitzpatrick type estimated from the photograph, not stated by the source) · Diasbuenasio · Wikimedia Commons - Vasculitis on legs.jpg · CC0 1.0

The severe end of the same disease, both feet. Dense purpura from the toes to the mid-shin with haemorrhagic blisters and early necrotic cru — The severe end of the same disease, both feet. Dense purpura from the toes to the mid-shin with **haemorrhagic blisters and early necrotic crusting** over the toes and dorsum. Note the dependent, symmetrical distribution below the knee: that gravitational pattern is characteristic. Blistering or necrosis means a more severe vasculitis and warrants urgent specialist discussion.
Fitzpatrick II (Fitzpatrick type estimated from the photograph, not stated by the source) · Profrofrof · Wikimedia Commons - HSP Vasculitis.jpg · CC0 1.0

Provenance for every photograph in this library: image licences. How much of the corpus still has no darker-skin photograph: skin tone coverage.

Mimics

Meningococcal septicaemia and purpura fulminans — Both give non-blanching purpura. IgA vasculitis is palpable, distributed over buttocks and extensor legs, and the child is not toxic
Benign mechanical petechiae — Mechanical petechiae are flat and confined above the nipple line
Acute urticaria — The early urticarial phase of IgA vasculitis can be mistaken for plain urticaria

What to do in the ED

Confirm the purpura is palpable and note the distribution - this is a clinical diagnosis
Check a blood pressure and dip the urine for blood and protein. Do both at every visit - this is the single most important thing the ED does for this condition
Take renal function if the urine is abnormal, the child is hypertensive, or the picture is atypical
Assess the abdomen carefully and image if intussusception is a possibility
Analgesia for joint and abdominal pain; the SHARE recommendations emphasise appropriate analgesia, and corticosteroids are not routine and are a specialist decision
Arrange planned urine and blood-pressure follow-up - nephritis can appear weeks after the rash has gone, so a normal dip today does not discharge the problem
Admit if there is severe abdominal pain, renal involvement, hypertension, or the child cannot be managed at home

Disposition

Most children are managed at home with analgesia and a planned schedule of blood pressure and urinalysis. Admit for severe abdominal pain, suspected intussusception, renal involvement or hypertension.

Safety-netting

Return immediately for severe or worsening tummy pain, vomiting, blood in the stool or urine, swelling of the face or legs, headache, or a child who becomes drowsy or unwell. The rash itself is not dangerous and will fade over weeks. Urine testing and blood pressure checks must continue as arranged even after the rash has gone completely, because the kidney can be affected later.

Local variation

The SHARE recommendations cited here are paediatric. IgA vasculitis in adults is less common, carries a higher risk of significant renal disease, and is managed differently - an adult presentation warrants nephrology or rheumatology discussion rather than the paediatric follow-up pathway. Follow-up schedules for urinalysis and blood pressure also vary between units; there is no single UK protocol. What must not vary is that follow-up is arranged before the patient leaves.

Sources

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