IgA Vasculitis: Triggers, Symptoms, and Kidney Risks

IgA vasculitis is a condition in which the immune system deposits a specific antibody, called immunoglobulin A, in the walls of small blood vessels, triggering inflammation that can affect the skin, joints, gut, and kidneys. You may know it by its older name, Henoch-Schönlein purpura (HSP). It is the most common form of small-vessel vasculitis in children, though it also strikes adults, often with a different clinical profile and a less predictable outcome. The disease is usually self-limiting, but kidney involvement can turn a seemingly mild illness into a long-term concern.

Why the Name Changed

For over a century this disease was called Henoch-Schönlein purpura, after two nineteenth-century German physicians. Johann Lukas Schönlein described the link between purpura and joint pain in 1837, and his student Eduard Henoch later added abdominal symptoms and kidney involvement to the picture.¹ The condition was actually observed even earlier, by the English physician William Heberden in the eighteenth century.² In 2012, the International Chapel Hill Consensus Conference renamed it “IgA vasculitis” to reflect the underlying mechanism rather than honor historical figures. Both names are still used in clinical practice, and you will see “HSP” in older medical records and plenty of current research papers.

What Happens Inside the Blood Vessels

The hallmark of IgA vasculitis is the deposit of IgA antibodies in the walls of small blood vessels. Specifically, patients produce an abnormal form of IgA1 that has sugar molecules missing from its structure, called galactose-deficient IgA1. The body then creates autoantibodies against this abnormal IgA1, and the resulting immune complexes circulate through the bloodstream. When these complexes lodge in vessel walls, they activate complement (a part of the immune system’s inflammatory cascade) and trigger the inflammation that damages tissues.³ In skin biopsies, this shows up as IgA deposits around blood vessels. One large Indian study found that about 90% of suspected cases showed positive IgA staining, and roughly 60% of those also had complement deposits.⁴

When these immune complexes settle in the kidney’s filtering units, the mesangial cells get activated, leading to cell proliferation and the overproduction of inflammatory signals. This kidney-specific process shares a great deal of biology with another condition called IgA nephropathy, which is why the two diseases are sometimes grouped together in research.

What Triggers It

The honest answer is that no single cause has been pinned down, but infections are the most commonly identified trigger. Upper respiratory infections appear to precede many cases, particularly in children. A study tracking respiratory pathogens alongside IgA vasculitis cases found that infections with influenza, adenovirus, and Mycoplasma pneumoniae tended to peak about a month before the surge in new IgA vasculitis diagnoses.⁵ Strep throat is perhaps the most frequently cited bacterial trigger, and many children develop the rash within a few weeks of a sore throat.

Genetics also plays a role. A particular gene variant in the HLA-DRB1 region, which helps the immune system distinguish self from non-self, is significantly more common in people with IgA vasculitis. One study found the HLA-DRB1*01 variant in about 43% of patients versus 7% of controls.⁶ A separate genome-wide study confirmed significant association at the HLA-DRB1 locus and identified specific amino-acid substitutions that increase risk.⁷ Having these gene variants does not guarantee you will develop the disease; it just means the immune system may be primed to overreact in a specific way when the right trigger comes along.

There is also growing interest in the gut microbiome. Children with IgA vasculitis tend to have a different composition of intestinal bacteria compared with healthy children, with certain genera like Enterococcus and Lactobacillus found in higher abundance.⁸ Whether these shifts help cause the disease or simply reflect an immune system already out of balance is still an open question, but the association has been consistent enough that it is attracting serious research attention.⁹

The Classic Symptoms

IgA vasculitis tends to announce itself with a distinctive rash: raised, non-blanching purplish spots (palpable purpura) that cluster on the legs and buttocks. In children, this rash is sometimes preceded by abdominal pain, which can confuse the initial diagnosis. In adults, purpura is almost always the first thing to appear, showing up as the presenting symptom in about 87% of adult cases compared with 56% of pediatric cases in one comparative study.¹⁰

Joint pain is extremely common. One study of 260 adults found that 62% had joint involvement, with the knees and ankles most often affected.¹¹ The good news about the joint symptoms is that they tend to resolve completely. In a large European cohort, arthritis remitted in every patient who received treatment, and not a single relapse involved the joints returning.¹²

Gastrointestinal symptoms show up in roughly two thirds of cases and result from inflammation of the small-bowel blood vessels, which causes the bowel wall to swell and sometimes bleed. In severe cases, the swollen bowel can fold in on itself, a complication called intussusception, which is the most common surgical emergency in IgA vasculitis.¹³ Intestinal perforation can follow intussusception, making prompt recognition important.¹⁴

Rare but Serious Complications

Most discussions of IgA vasculitis focus on skin, joints, gut, and kidneys. But the disease can show up in unexpected places. Scrotal involvement in boys, neurological symptoms, and cardiopulmonary disease have all been reported.¹⁵ Perhaps the most alarming rare complication is diffuse alveolar hemorrhage, where the tiny vessels in the lungs bleed into the air sacs. Case reports have documented this in adults, sometimes without the classic rash, making diagnosis very difficult. One patient presented only with coughing up blood and a low-grade fever; a kidney biopsy was needed to confirm the diagnosis.¹⁶ Pulmonary hemorrhage can be fatal even with aggressive treatment including steroids, cyclophosphamide, and plasma exchange.¹⁷ These outcomes are rare, but they underscore why any unusual symptom in a patient with known IgA vasculitis deserves prompt attention.

Kidney Involvement Is the Main Long-Term Worry

In most children and many adults, IgA vasculitis resolves on its own within weeks. The exception is the kidneys. When IgA-containing immune complexes deposit in the glomeruli, they cause a form of nephritis that can range from mild blood or protein in the urine to rapidly progressive kidney failure. In children, this kidney involvement tends to be self-limiting and resolves favorably. In adults, the picture is often more severe and can lead to lasting kidney damage.¹⁸

A study of patients who underwent kidney biopsy for IgA vasculitis nephritis found that long-term kidney outcomes were determined by clinical risk factors along with specific biopsy findings, including endocapillary hypercellularity and fibrous crescents, features that are not part of the standard pediatric classification system used to grade kidney biopsies in this disease.¹⁹ That gap between what biopsy classification looks at and what actually predicts outcomes is one of the active areas of research in the field.

How It Gets Diagnosed

Diagnosis usually starts clinically: a doctor sees the characteristic rash, especially on the lower limbs and buttocks, and combines that with joint pain, abdominal symptoms, or kidney findings. The most widely used formal criteria come from a 2010 international consensus (EULAR/PRINTO/PRES). These criteria require palpable purpura plus at least one of four other features: abdominal pain, IgA deposits on biopsy, joint involvement, or kidney involvement. In adults, these criteria have a sensitivity of about 99% and a specificity of 86%, outperforming the older American College of Rheumatology criteria from 1990.²⁰

Skin biopsy with direct immunofluorescence remains important, especially in ambiguous cases. A retrospective study of 112 biopsy specimens found that no routine microscopic feature on standard light microscopy could reliably predict whether IgA deposits would be present; immunofluorescence was necessary to confirm the diagnosis.²¹ In other words, looking at the tissue under a normal microscope is not enough; you need the specialized fluorescence test to see the IgA.

For tracking kidney involvement, researchers are looking beyond traditional measures like urine protein levels. Urinary biomarkers such as kidney injury molecule-1 (KIM-1), monocyte chemotactic protein-1 (MCP-1), and N-acetyl-β-glucosaminidase (NAG) have shown promise in predicting which patients have nephritis and how severe it is.²² Complement-related proteins in urine, particularly mannose-binding lectin and pentraxin-3, may also serve as markers of active kidney disease.²³ None of these are in routine clinical use yet, but they could eventually allow doctors to monitor kidney damage with a simple urine test rather than a biopsy.

Adults Versus Children

IgA vasculitis peaks in children between ages three and ten, and most pediatric cases are mild and self-resolving. Adults develop it less often, but when they do, the presentation tends to differ in ways that matter. Adults have significantly more joint involvement (90% vs. 44% in one cohort), and the rash is almost always the first symptom rather than abdominal pain.²⁴ The frequency of kidney involvement is roughly similar between the two groups, but the consequences diverge: children’s kidneys usually recover, while adults face a higher risk of lasting damage.²⁵ Despite these differences, complete recovery rates were reassuringly high in both groups in at least one comparative study, at around 83-86%.²⁶

Treatment Options

For mild disease, treatment is mostly supportive: rest, hydration, and pain relief. The trickier question is whether corticosteroids should be given early to prevent kidney involvement. The evidence here is genuinely mixed. One review found moderate evidence that steroids do not prevent kidney problems when given for non-kidney symptoms.²⁷ A more recent study confirmed this, finding that early steroids for extrarenal symptoms did not prevent, delay, or mask later kidney involvement, though they may shift the pattern toward milder forms of kidney disease.²⁸

Once kidney disease is established, however, experts do recommend corticosteroids to prevent long-term damage, drawing on the parallels with IgA nephropathy treatment.²⁹ For more severe or steroid-resistant cases, mycophenolate mofetil (MMF) has emerged as a useful add-on. A meta-analysis of ten studies covering 675 pediatric patients found that MMF combined with corticosteroids achieved higher rates of complete remission with fewer side effects compared to cyclophosphamide combinations.³⁰ In adults with significant proteinuria, MMF with low-dose steroids outperformed standard blood-pressure medications alone in reducing protein in the urine after a year of treatment.

A Cochrane systematic review, which is the gold standard for synthesizing clinical trial evidence, looked at the broader treatment landscape and found the evidence frustratingly thin. For severe kidney disease, comparisons between cyclophosphamide and supportive care showed no clear difference in outcomes in either children or adults. Head-to-head comparisons between different immunosuppressive drugs were limited by very small study sizes, making it hard to draw firm conclusions.³¹ The bottom line is that treatment decisions for severe IgA vasculitis nephritis are still guided more by expert opinion and experience than by large, definitive trials.

Recurrence and What Predicts It

IgA vasculitis can come back. A multicenter study of 229 adults identified several factors that raised the risk of recurrence. Purpura extending to the abdomen roughly doubled the risk, as did joint involvement. Fever at diagnosis was associated with about a threefold higher risk of relapse. On the other hand, cases triggered by a documented bacterial infection carried a lower recurrence risk, possibly because the underlying trigger was transient. Systemic corticosteroids were associated with a reduced risk of recurrence, while colchicine, which is sometimes prescribed to prevent flares, showed no significant benefit.³²

When relapses do occur, they tend to be limited to skin and kidney symptoms. In the European arthritis cohort, about 24% of patients with joint involvement relapsed within two years, but none of those relapses involved the joints.³³ This pattern suggests that the joint component is one-and-done for most people, while the skin and kidneys are the organs to keep watching.

Pregnancy After IgA Vasculitis

Women who have had IgA vasculitis and are considering pregnancy face a legitimate but manageable set of added risks. A population-level study found that women with a history of IgA vasculitis had roughly double the odds of spontaneous abortion and preterm delivery, and nearly five times the odds of gestational hypertension compared with women who had never had the disease.³⁴ A separate case-control study found that gestational hypertension and pre-eclampsia were both more common in women with a history of IgA vasculitis, particularly in those who had pre-existing kidney disease; hypertensive complications occurred in 78% of those patients versus 12% of those without kidney problems.³⁵

The reassuring findings from both studies are that no fetal deaths or maternal deaths were reported, the disease rarely flares during pregnancy itself, and fertility does not appear to be reduced. The key takeaway for women planning a pregnancy after IgA vasculitis is that closer obstetric monitoring is warranted, especially if there was any kidney involvement during the original episode.

Emerging Biomarkers and Future Directions

One of the frustrations in managing IgA vasculitis is the lack of reliable blood or urine tests that can tell you how active the disease is or predict who will develop kidney problems. The current standard, checking for protein and blood in the urine, works but only catches kidney involvement once it has already started. Researchers are exploring whether complement-related proteins in urine might detect kidney inflammation earlier. Urinary levels of pentraxin-3 and mannose-binding lectin appear to correlate with active inflammation in kidney biopsies, while another complement fragment, C4c, was linked to the severity of chronic scarring in the kidneys and independently predicted how fast kidney function declined over time.³⁶ If validated in larger studies, a panel of urine biomarkers could eventually guide treatment decisions, flagging patients who need aggressive therapy before irreversible damage accumulates, and sparing those whose kidneys are not truly at risk from unnecessary immunosuppression.

1
PubMed Central. A Review of IgA Vasculitis (Henoch-Schönlein Purpura) Past, Present, and Future ↩︎
2
British Journal of Dermatology. H20: Henoch–Schönlein purpura: what’s in a name? ↩︎
3
PubMed Central. Autoantibodies Specific for Galactose-Deficient IgA1 in IgA Vasculitis With Nephritis ↩︎
4
PubMed Central. Direct Immunofluorescence in Cutaneous Vasculitis: Experience from a Referral Hospital in India ↩︎
5
PubMed Central. The influence of respiratory infections on Henoch-Schönlein purpura in children ↩︎
6
PubMed. HLA-DRB1 association with Henoch-Schonlein purpura ↩︎
7
PubMed Central. Genome-wide studies define new genetic mechanisms of IgA vasculitis ↩︎
8
PubMed Central. Taxonomic and functional shifts of gut microbiome in immunoglobulin A vasculitis children and their mothers ↩︎
9
PubMed Central. Landscape of intestinal microbiota in patients with IgA nephropathy, IgA vasculitis and Kawasaki disease ↩︎
10
PubMed. Differences between adult and pediatric onset Henoch-Schonlein purpura from North India ↩︎
11
PubMed. Clinical phenotype and cytokine profile of adult IgA vasculitis with joint involvement ↩︎
12
Annals of the Rheumatic Diseases. ARTHRITIS IN ADULT IGA VASCULITIS ↩︎
13
PubMed Central. Immunoglobulin A Vasculitis-Associated Ileoileal Intussusception in an Adult Male: Case Report ↩︎
14
PubMed. Clinical characteristics and risk factors of IgA vasculitis with intussusception and intestinal perforation ↩︎
15
PubMed. Multisystemic manifestations of IgA vasculitis ↩︎
16
PubMed Central. Diffuse Alveolar Hemorrhage in IgA Vasculitis with an Atypical Presentation ↩︎
17
PubMed Central. Pulmonary Hemorrhaging as a Fatal Complication of IgA Vasculitis ↩︎
18
PubMed. IgA vasculitis nephritis in children and adults: one or different entities? ↩︎
19
PubMed Central. Histologic and Clinical Factors Associated with Kidney Outcomes in IgA Vasculitis Nephritis ↩︎
20
PubMed Central. IgA vasculitis in adults: the performance of the EULAR/PRINTO/PRES classification criteria in adults ↩︎
21
PubMed. Histopathologic features predictive of perivascular deposition of IgA on direct immunofluorescence in cases of leukocytoclastic vasculitis: A retrospective study of 112 specimens ↩︎
22
PubMed Central. A systematic review of urine biomarkers in children with IgA vasculitis nephritis ↩︎
23
Nephrology Dialysis Transplantation. Complement biomarkers in IgA nephropathy and IgA vasculitis with renal involvement: can urine rather than blood be the answer? ↩︎
24
PubMed. Differences between adult and pediatric onset Henoch-Schonlein purpura from North India ↩︎
25
PubMed. IgA vasculitis nephritis in children and adults: one or different entities? ↩︎
26
PubMed. Differences between adult and pediatric onset Henoch-Schonlein purpura from North India ↩︎
27
PubMed Central. Henoch-Schönlein purpura in children: Use of corticosteroids for prevention and treatment of renal disease ↩︎
28
PubMed. Patterns of kidney involvement after corticosteroid treatment for extrarenal symptoms in pediatric IgA vasculitis (Henoch-Schönlein Purpura): phenotypes and outcomes ↩︎
29
PubMed Central. Henoch-Schönlein purpura in children: Use of corticosteroids for prevention and treatment of renal disease ↩︎
30
PubMed Central. IgA Vasculitis (Henoch–Schönlein Purpura): An Update on Treatment ↩︎
31
Cochrane Database of Systematic Reviews. Interventions for preventing and treating kidney disease in IgA vasculitis (Henoch‐Schönlein Purpura) ↩︎
32
PubMed. Risk factors for recurrence or relapse after a first episode of adult IgA vasculitis: A multicenter retrospective study ↩︎
33
Annals of the Rheumatic Diseases. ARTHRITIS IN ADULT IGA VASCULITIS ↩︎
34
PubMed. Pregnancy outcomes in women with a history of immunoglobulin A vasculitis ↩︎
35
PubMed. Pregnancy outcome in patients with a medical history of immunoglobulin A vasculitis: a case-control study ↩︎
36
Clinical Kidney Journal. Urine complement-related proteins in IgA nephropathy and IgA vasculitis nephritis, possible biomarkers of disease activity ↩︎