Educational draft · awaiting clinical reviewThe full textbook explains uncertainty but does not replace live national or local guidance, specialist advice, or current prescribing information.
Recognise IgA vasculitis from palpable purpura with joint, gastrointestinal and renal involvement, exclude sepsis and other small-vessel disease, detect adult nephritis and bowel emergencies, and organise supportive, organ-specific and long-term renal care.
IgA vasculitis is an IgA-immune-complex small-vessel vasculitis affecting skin, joints, bowel and kidneys. Palpable purpura is usually symmetrical and dependent but can extend to arms and trunk. Ankle and knee arthralgia is common and non-destructive. Abdominal symptoms may precede rash, creating diagnostic uncertainty. Renal involvement ranges from microscopic haematuria to rapidly progressive crescentic glomerulonephritis.
Diagnosis is clinical in a typical presentation, supported by normal or non-causative platelets and targeted biopsy. Send cultures and treat sepsis immediately when the patient is toxic. FBC, coagulation and film identify bleeding and TMA mimics. Urine and blood pressure are mandatory even when the complaint is rash or joint pain. Serum IgA can be raised but is neither sensitive nor specific and does not replace tissue.
Biopsy strategy follows consequence. A fresh purpuric lesion sampled for routine histology and direct immunofluorescence demonstrates leukocytoclastic vasculitis with vascular IgA. Kidney biopsy is preferred when nephritis severity may justify immunosuppression because it shows mesangial IgA, crescents and chronicity. Abdominal imaging evaluates bowel complications rather than confirming immune mechanism.
Upper-respiratory and gastrointestinal infections frequently precede disease, with mucosal IgA responses becoming dysregulated; no single organism explains all cases.
Selected medicines and immune stimuli are temporal triggers in some patients, but causality requires careful chronology and competing infection assessment.
IgA vasculitis is commonest in children but adults develop more severe renal disease; genetic and mucosal immune factors modify risk and recurrence.
Abnormally glycosylated IgA1 becomes antigenic, generating circulating immune complexes that deposit in small vessels and glomerular mesangium.
IgA-containing deposits activate alternative and lectin complement pathways, recruiting neutrophils and causing leukocytoclastic capillary and venular inflammation.
Skin purpura, synovial inflammation, bowel-wall oedema and haemorrhage and glomerular blood or protein reflect the affected vascular bed.
Mesangial proliferation, endocapillary inflammation and crescents can progress to segmental scar and tubulointerstitial fibrosis, determining long-term kidney risk.
Raised non-blanching lesions concentrated on legs and buttocks with normal platelets supports cutaneous small-vessel vasculitis.
Transient painful swelling of ankles and knees commonly accompanies rash without erosive or permanently destructive arthritis.
Colicky pain, vomiting, occult or overt bleeding and bowel-wall oedema can precede purpura and may progress to intussusception.
Microscopic blood, protein, hypertension, oedema or creatinine change may emerge days to weeks after other symptoms.
A toxic patient with rapidly evolving non-blanching rash is treated immediately for sepsis; distribution and IgA tests must not delay antibiotics.
ANCA disease, cryoglobulinaemia, lupus and hypersensitivity vasculitis cause purpura and renal or systemic injury with different serology and biopsy deposits.
ITP, TTP, DIC, anticoagulation and haematological disease produce non-blanching lesions through bleeding rather than vessel-wall IgA inflammation.
IgA nephropathy shares renal biology but lacks the defining systemic purpura, abdominal and joint vasculitic syndrome at presentation.
Toxic physiology, fever and rapidly spreading petechiae or ecchymoses require immediate sepsis treatment regardless of a possible vasculitis history.
Persistent proteinuria, hypertension, reduced eGFR and crescentic nephritis can lead to CKD and kidney failure, particularly after adult disease.
Bowel-wall oedema creates a lead point for intussusception, while vasculitis can cause haemorrhage, ischaemia, perforation and pancreatitis.
Scrotal oedema, orchitis, CNS disease, pulmonary haemorrhage and cardiac involvement are uncommon but require urgent alternative exclusion and organ care.
Purpura, joints and abdominal symptoms can recur, while unnecessary glucocorticoid exposes infection and metabolic toxicity without preventing later nephritis.
Abdominal pain or arthritis may precede purpura, so repeat skin and urine examination when the early diagnosis remains uncertain.
IgA vasculitis classically has a normal platelet count; thrombocytopenia demands a bleeding, sepsis or microangiopathy pathway.
Treating rash or abdominal symptoms has not reliably prevented later nephritis, making scheduled urine and pressure checks essential.
Adult disease is less common but more likely to leave proteinuria, hypertension, CKD and kidney failure than typical childhood disease.
Skin supports the systemic IgA mechanism; kidney tissue grades active crescents and chronic scar to guide renal treatment.
Reassuring a toxic patient with purpura before treating possible meningococcal sepsis.
Omitting urine and pressure because the presentation is limited to rash and ankles.
Using a normal initial urinalysis to cancel follow-up.
Giving glucocorticoid solely to prevent nephritis.
Attributing severe colicky abdominal pain to vasculitis without imaging for intussusception or ischaemia.
Using NSAIDs in a dehydrated patient with GI bleeding or renal involvement.
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An adult with biopsy-supported cutaneous IgA vasculitis has normal urine and creatinine at presentation and the rash resolves. What follow-up is most appropriate?
National guidance is shown before implementation-dependent detail. Typical adult dose examples remain subject to patient factors, contraindications and the live BNF or specialist protocol. Source check completed 27 Aug 2026; clinical approval remains outstanding.
Editorial contact: Doctor’s Passport editorial team. Source-check date is separate from clinical approval. Report a content problem · Content changes
Most cutaneous and joint disease resolves with supportive care. Severe abdominal symptoms can respond to glucocorticoid once intussusception, perforation and infection are excluded. Preventive steroid does not reliably stop nephritis. Renal management follows proteinuria, pressure, eGFR and pathology, with ACE inhibition or ARB and nephrology-selected immunosuppression for severe active disease. Adults need particularly careful long-term renal follow-up.
Count all combination products and avoid overdose; review liver disease, alcohol, malnutrition and body weight. Analgesia must not delay assessment of peritonism or renal deterioration.
Monitor infection, GI bleeding, glucose, pressure, mood and bone and reassess pain that fails to improve. Do not allow symptom suppression to obscure intussusception or perforation.
Check creatinine and potassium before and one to two weeks after start or titration; review volume depletion, hyperkalaemia, bilateral renal-artery stenosis and angioedema. Stop before conception and immediately if pregnancy occurs.
Obtain cultures and biopsy where safe, monitor rhythm, pressure, glucose, psychiatric, infection and GI effects and combine only with a defined nephrology treatment and taper plan.