Paediatrics chapters
Henoch-Schonlein purpura (IgA vasculitis)
The commonest vasculitis of childhood: IgA immune complexes in small vessels cause palpable purpura on the legs and buttocks, arthritis, abdominal pain and nephritis; how it is diagnosed with a normal platelet count, treated supportively and followed for kidney disease and intussusception.
- HSP (IgA vasculitis) is the commonest vasculitis of childhood: IgA immune complexes in small vessels of skin, gut, joints and kidney, usually at 3-15 years, often after an upper respiratory infection.
- Classic picture: palpable, non-blanching purpura on the buttocks and legs, arthritis of knees and ankles, colicky abdominal pain, and haematuria; the platelet count is normal or high and clotting is normal.
- Treatment is mostly supportive; prednisone 1 mg/kg/day for severe abdominal pain; watch for intussusception, perforation, testicular torsion and nephritis, and check urine and blood pressure during follow-up because the kidney decides the long-term outlook.
On this page
Overview
Henoch-Schonlein purpura (HSP), now also called IgA vasculitis and formerly anaphylactoid purpura, is an inflammation of small blood vessels (capillaries, venules, arterioles) of the skin, gut, joints and kidneys, with deposits of IgA. It is the commonest vasculitis seen in children and the commonest cause of non-thrombocytopenic purpura.
Most children recover fully within weeks. The exam tests the classic tetrad (rash, arthritis, abdominal pain, renal disease), the normal platelet count, the gut and renal complications, and when to give steroids.
Definition
A small-vessel vasculitis of unknown cause in which immune complexes containing mainly IgA are deposited in vessel walls, causing white cell infiltration, bleeding into tissues and ischaemia. It is classed with the hypersensitivity vasculitides.
Epidemiology
- Nelson: about 13 per 100,000 children.
- Mainly 3-15 years; onset is usually after 3 years of age.
- Slight male predominance.
- More common in winter.
- Often follows an upper respiratory tract infection 1-3 weeks earlier.
Pathogenesis
- Triggers suggested: group A beta-haemolytic streptococcus, Staphylococcus aureus, Mycoplasma, adenovirus and other viruses; also drugs, foods and insect bites. The exact cause is unknown.
- Polymeric IgA immune complexes deposit in small vessels.
- Immunofluorescence shows IgA and C3 in vessels of the skin and in the renal glomeruli (mesangium).
- Histology: leucocytoclastic vasculitis with neutrophils infiltrating the walls of small arterioles and venules.
- The kidney lesion looks the same as IgA nephropathy.
"IgA in the Skin, Gut, Joints and Kidney": the four organs of HSP.
Clinical findings
Skin (almost all; the hallmark)
- Often the first and commonest feature, but in at least a quarter of children the rash appears after joint or abdominal symptoms (Akbar), which makes early diagnosis harder.
- Starts as urticarial or small macular lesions, then becomes palpable, non-blanching purpura with petechiae and bruise-like patches.
- Symmetric, in dependent areas: buttocks, back of the legs, ankles and feet, and extensor surfaces of elbows and knees; can spread to the whole body.
- New crops appear for 2-4 weeks; the rash can wax and wane for up to a year.
- Subcutaneous oedema of the scalp, forehead, around the eyes, lips, backs of hands and feet, calves, and scrotum or labia.
Joints (about two-thirds to 80%)
- Arthritis or arthralgia of large lower limb joints, especially knees and ankles.
- Very painful, the child may refuse to walk; may be migratory.
- Transient; leaves no permanent damage and does not usually recur.
- Joint swelling can be confused with the soft tissue oedema of the rash.
Gut (about half)
- Colicky abdominal pain from oedema and bleeding in the small bowel wall (bowel ischaemia, "bowel angina").
- Occult blood in stool, bloody diarrhoea, vomiting or haematemesis.
- Intussusception (usually of the small intestine), perforation and severe bleeding are less common but serious.
- Gut symptoms occur in the acute phase and may come before the rash.
Kidney (about a third to a half)
- Usually appears within the first few weeks to months (Akbar: after 2-3 weeks of illness).
- Ranges from isolated microscopic haematuria to proteinuria, nephritic or nephrotic syndrome, hypertension and acute renal failure.
- Rarely, renal disease appears late, so urine checks continue after the rash fades.
Other
- Orchitis, scrotal swelling and testicular torsion.
- Neurological: headache, behaviour change, seizures, encephalopathy, intracranial bleeding (rare).
- Pancreatitis (rare).
Purpura on the buttocks and legs + painful knees/ankles + colicky abdominal pain + haematuria, with a normal platelet count = HSP.
Diagnostic criteria
The diagnosis is clinical, easy when the typical rash is present. The criteria in both books need two of four:
| Criterion | Definition |
|---|---|
| Palpable purpura | Raised haemorrhagic skin lesions without thrombocytopenia |
| Bowel angina | Diffuse abdominal pain (often after meals) or bowel ischaemia, bloody diarrhoea |
| Diagnostic biopsy | Granulocytes infiltrating small arteriole or venule walls, with IgA deposits |
| Age at onset | Under 20 years |
Two of four gives about 87% sensitivity and specificity (Nelson).
Investigations
| Test | Finding |
|---|---|
| Platelet count | Normal or raised: the most important test, separating HSP from thrombocytopenic purpuras |
| Coagulation (PT, APTT) | Normal |
| Full blood count | Usually normal; anaemia if there is gut bleeding |
| ESR, CRP, white count | Normal or raised |
| Serum IgA | Often raised |
| C3 | Normal (unlike post-streptococcal GN and lupus) |
| ASO titre, throat swab | ASO often raised; throat culture may grow group A streptococcus |
| Urinalysis | Haematuria with or without proteinuria; repeated during follow-up |
| Urea, creatinine; blood pressure | To assess renal function |
| Stool for occult blood | Often positive |
| Abdominal ultrasound | To look for intussusception |
| Plain X-ray or other imaging | If perforation is suspected |
| Skin biopsy | IgA in vessel walls (when the diagnosis is uncertain) |
| Renal biopsy | For severe or persistent nephritis: mesangial IgA, with C3 and fibrin |
Purpura with a low platelet count is not HSP. Think of ITP, leukaemia, SLE or meningococcal sepsis.
Differential diagnosis
| Condition | Key difference |
|---|---|
| Immune thrombocytopenic purpura | Low platelets; purpura is flat (not palpable) and widespread |
| Leukaemia | Cytopenias, blasts, organomegaly, bone pain |
| Meningococcaemia and other septicaemia | Very ill, shocked child with rapidly spreading purpura; needs immediate antibiotics |
| Haemolytic uraemic syndrome | Haemolysis with fragmented red cells, low platelets, acute kidney injury |
| SLE | Low complement, ANA positive, cytopenias |
| Other vasculitides | Polyarteritis nodosa, Kawasaki disease |
| Child abuse or trauma | Bruises in unusual places, history inconsistent |
| Surgical abdomen | When abdominal pain precedes the rash |
Management
Supportive (most children)
- Adequate hydration and a bland diet during abdominal pain.
- Pain relief: paracetamol; NSAIDs for painful arthritis (short course).
- Rest; avoid keeping the legs hanging down (reduces oedema) and avoid competitive sport in the acute phase.
- Penicillin if throat culture grows group A streptococcus or ASO is raised (Akbar).
Corticosteroids
- Indications: severe abdominal pain or gut involvement, orchitis, severe renal disease, severe joint symptoms.
- Dose (both books): prednisone 1 mg/kg/day for 1-2 weeks, then taper. Abdominal pain may return as the dose is reduced and need a longer course.
- Steroids give quick relief of gut and joint symptoms but do not help the rash (Akbar adds that they do not help the renal manifestations).
Steroids do not clear the rash and are not a way to prevent HSP nephritis; they are for severe gut, joint or testicular symptoms and for established severe nephritis.
- Chronic or recurrent HSP may respond to pulse IV methylprednisolone 30 mg/kg/day (maximum 1 g) for 3 days, then weekly and tapered.
Renal involvement
| Severity | Approach |
|---|---|
| Mild (isolated haematuria, minimal proteinuria) | No specific treatment; usually resolves; follow up urine and blood pressure |
| Persistent proteinuria | ACE inhibitor and/or ARB |
| Moderate to severe nephritis (nephrotic range, impaired function) | High-dose corticosteroids with immunosuppressants such as cyclophosphamide, azathioprine, ciclosporin or mycophenolate; plasmapheresis or rituximab in selected cases; refer to a paediatric nephrologist |
Urgent complications
| Complication | Clue | Action |
|---|---|---|
| Intussusception | Sudden severe colic, vomiting, blood in stool | Ultrasound; hydrostatic reduction or surgical resection |
| Bowel perforation or infarction | Peritonism, distension | Imaging, urgent surgery |
| Massive gut bleeding | Haematemesis, melaena, falling haemoglobin | Resuscitate, transfuse, steroids |
| Testicular torsion or orchitis | Acute painful scrotum | Urgent surgical review |
| Acute renal failure, nephrotic syndrome, hypertension | Oliguria, oedema, high BP | Nephrology care, steroids and immunosuppression |
| Neurological involvement | Seizures, reduced consciousness | Imaging, supportive care |
A child with recent HSP who develops acute abdominal pain, constipation or diarrhoea must be checked for intussusception.
Prognosis
- Self-limiting and monophasic in most: the illness lasts about 3-4 weeks and resolves completely.
- Recurrences are common, usually within the first weeks to months (Akbar quotes 15-60% within 4-6 weeks); warn the parents.
- Arthritis leaves no damage.
- Long-term outlook depends on the kidney:
- Most renal involvement (isolated haematuria, mild proteinuria) resolves completely.
- Chronic renal disease develops in a small minority; progressive renal failure in fewer than 5% (Akbar) and end-stage renal disease in under 1% (Nelson).
- Highest risk: severe initial nephritis, raised urea, persistent heavy proteinuria, nephrotic syndrome.
- HSP can recur in a transplanted kidney.
- Follow-up: urinalysis and blood pressure at intervals for months after the illness, longer if urine stays abnormal.
Expect: a school-age child with purpura on the buttocks and legs, painful ankles and abdominal pain after a cold; IgA deposition in small vessels; normal platelet count and clotting as the key test; intussusception (small bowel) and gut bleeding as urgent complications; testicular involvement; renal involvement with haematuria and its role in prognosis; normal C3; supportive care with steroids for severe abdominal pain (prednisone 1 mg/kg/day); steroids not helping the rash; urine and BP follow-up; two of four criteria including age under 20.
Quick revision
- Commonest childhood vasculitis; IgA immune complexes in small vessels.
- Age 3-15, boys slightly more, winter, after a respiratory infection.
- Palpable non-blanching purpura on buttocks and legs, with oedema.
- Painful transient arthritis of knees and ankles; no lasting damage.
- Colicky abdominal pain in about half; intussusception and perforation are emergencies.
- Kidney: haematuria, proteinuria, nephritis; decides long-term prognosis.
- Platelets normal or high, clotting normal, C3 normal, IgA often raised.
- Supportive care; prednisone 1 mg/kg/day for severe gut pain, orchitis, severe nephritis.
- Follow urine and blood pressure for months.
Written by The House Job from standard references (Basis of Paediatrics by Pervez Akbar; Nelson Essentials of Paediatrics).
FAQ
Why is the platelet count so important in HSP?
HSP is a purpura with a normal or high platelet count. A low count points to another diagnosis such as ITP, leukaemia, SLE or sepsis.
Do steroids prevent kidney damage in HSP?
They relieve severe abdominal and joint pain quickly but do not help the rash and are not given to prevent nephritis. Established severe nephritis is treated with high-dose steroids and other immunosuppressants.
How long should a child with HSP be followed up?
Until the urine and blood pressure are normal over several months, because kidney involvement can appear weeks after the rash. Persistent proteinuria or abnormal renal function needs longer specialist follow-up.
Will HSP come back?
Recurrences of rash and abdominal pain are common in the first weeks to months but usually milder. Most children recover completely without lasting harm.