IgA-mediated small-vessel vasculitis with palpable purpura, arthralgia, abdominal pain, and IgA nephropathy.
Also known as: HSP, Henoch-Schönlein purpura, IgA vasculitis, anaphylactoid purpura, IgAV
Overview
A small-vessel vasculitis characterized by IgA1-dominant immune deposits in vessel walls and the glomerular mesangium. Per the 2012 Chapel Hill consensus, it is the systemic counterpart of IgA nephropathy. Classic tetrad: palpable purpura, arthralgia/arthritis, abdominal pain, and glomerulonephritis.
Epidemiology
The most common childhood vasculitis. Annual incidence ~20 per 100,000 in children aged 3-15 years (peak 4-6). Adult cases are less common but tend to be more severe with higher rates of renal involvement. Slight male predominance. Often follows an upper respiratory infection.
Try two board-style IgA Vasculitis questions
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Question 1RenalMedium
A 6-year-old boy is brought in for a rash that appeared 10 days after an upper respiratory infection. He has crops of raised, non-blanching purple spots concentrated on his buttocks and lower legs, and he has been limping because of painful, swollen ankles and knees. Over the past 2 days he has had crampy abdominal pain. He is afebrile and hemodynamically stable. Urinalysis shows 2+ blood and 1+ protein with dysmorphic red cells; platelet count and coagulation studies are normal. Which of the following is the most likely diagnosis?
AImmune thrombocytopenic purpura
BIgA leukocytoclastic vasculitis
CDisseminated meningococcal disease
DAcute hemorrhagic edema of infancy
Reveal answer & full explanation
Correct answer: B — IgA leukocytoclastic vasculitis
AImmune thrombocytopenic purpura
BIgA leukocytoclastic vasculitis✓
CDisseminated meningococcal disease
DAcute hemorrhagic edema of infancy
Why IgA leukocytoclastic vasculitis is correct
This is the classic tetrad of an IgA-dominant small-vessel vasculitis: palpable, non-blanching purpura on dependent/pressure areas (buttocks, lower legs), arthralgia/arthritis of large joints, crampy abdominal pain, and glomerulonephritis (hematuria with dysmorphic RBCs and proteinuria).
It is the most common childhood vasculitis and characteristically follows an upper respiratory infection by days to a couple of weeks.
Normal platelet count and coagulation studies are a key discriminator — the purpura is from leukocytoclastic vessel-wall inflammation, not a bleeding/clotting defect. Diagnosis is clinical (EULAR/PRINTO/PReS 2010 criteria: palpable purpura plus abdominal pain, arthritis/arthralgia, renal involvement, or IgA-predominant biopsy).
Why the others are wrong
Immune thrombocytopenic purpura — causes non-palpable petechiae/purpura, but the platelet count is LOW; here platelets and coagulation are normal, and ITP does not produce arthritis, abdominal pain, or nephritis.
Acute hemorrhagic edema of infancy — a benign small-vessel vasculitis of children under 2 years with large cockade/medallion purpura and limb edema, but it spares the kidneys and GI tract and would not explain hematuria, arthritis, and abdominal pain in a 6-year-old.
Disseminated meningococcal disease — also causes palpable/retiform purpura, but the child would be febrile, toxic, and hemodynamically unstable with rapidly evolving lesions; this patient is afebrile and stable, and meningococcemia does not cause this arthritis-plus-nephritis picture.
Question 2RenalMedium
A 6-year-old boy is brought in for a rash that appeared 10 days after an upper respiratory infection. He has crampy abdominal pain and aching knees and ankles. Exam shows symmetric, palpable, non-blanching purpura over the buttocks and lower legs. Urinalysis reveals microscopic hematuria with 1+ protein. Which of the following laboratory findings is most consistent with this diagnosis?
AProlonged PT and PTT
BLow serum complement
CNormal platelet count
DPositive ANCA serology
Reveal answer & full explanation
Correct answer: C — Normal platelet count
AProlonged PT and PTT
BLow serum complement
CNormal platelet count✓
DPositive ANCA serology
Why Normal platelet count is correct
The clinical picture — palpable purpura, arthralgia, abdominal pain, and hematuria after a URI in a child — is the classic tetrad of IgA vasculitis (Henoch-Schönlein purpura).
IgA vasculitis is a small-vessel leukocytoclastic vasculitis driven by IgA immune-complex deposition, not a platelet or coagulation disorder, so the platelet count and clotting studies are characteristically normal.
A normal platelet count is the key discriminator that separates this palpable (non-thrombocytopenic) purpura from thrombocytopenic causes such as ITP and TTP. Per EULAR/PRINTO/PReS 2010 criteria, the diagnosis rests on palpable purpura plus abdominal pain, arthritis/arthralgia, renal involvement, or IgA-predominant deposits on biopsy.
Why the others are wrong
Positive ANCA serology: ANCA characterizes pauci-immune ANCA-associated vasculitis, which tends to occur in older patients with pulmonary-renal disease; it is negative in IgA vasculitis.
Low serum complement: low complement points toward lupus or cryoglobulinemic vasculitis; C3 and C4 are typically normal in IgA vasculitis.
Prolonged PT and PTT: coagulation studies are normal in IgA vasculitis; prolonged clotting times would suggest a coagulopathy or DIC, as in meningococcemia, rather than this immune-complex vasculitis.
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Underlying malignancy in adults (especially lung cancer; consider workup)
Pathophysiology
Aberrantly galactosylated IgA1 (Gd-IgA1) is produced — typically following mucosal infection — and recognized as a neoantigen by IgG and IgA autoantibodies. The resulting circulating immune complexes deposit in the skin, joints, gut, and renal mesangium, activating complement (primarily alternative pathway) and producing leukocytoclastic small-vessel vasculitis and mesangial proliferative glomerulonephritis indistinguishable on biopsy from primary IgA nephropathy.
Clinical presentation
Symptoms
Palpable, non-blanching purpura predominantly on lower extremities and buttocks (universal feature)
Arthralgia or arthritis of large joints (knees, ankles) — transient and non-deforming
Crampy abdominal pain — can mimic surgical abdomen; intussusception is a feared complication (often ileoileal in HSP)
Gross or microscopic hematuria, proteinuria; nephrotic-range protein loss in severe cases
Drug-induced cutaneous vasculitis — Recent new medication, lesions confined to skin, resolves with withdrawal
Thrombocytopenic purpura (ITP, TTP) — Low platelets in ITP; schistocytes and thrombocytopenia in TTP
Diagnostic workup
Diagnostic criteria
EULAR/PRINTO/PReS 2010 criteria (pediatric): palpable purpura plus at least one of (1) diffuse abdominal pain, (2) any biopsy showing predominant IgA deposition, (3) arthritis or arthralgia, or (4) renal involvement (hematuria or proteinuria). Adult cases benefit from skin biopsy (leukocytoclastic vasculitis with IgA deposits) and/or renal biopsy in clinically significant nephritis.
Labs
CBC (platelets usually normal — important; helps exclude ITP/TTP)
Abdominal ultrasound if severe abdominal pain — evaluate for intussusception (target sign or pseudokidney sign)
CT in equivocal cases
Renal ultrasound if hypertension or impaired GFR
Diagnostic algorithm
Tetrad component
Frequency
Key clinical pearls
Palpable purpura
100% (defining)
Symmetric, dependent areas (legs, buttocks); non-blanching
Arthritis / arthralgia
60-85%
Large joints (knees, ankles); transient, nondestructive
Abdominal pain
50-75%
Crampy; watch for intussusception (typically ileoileal) and GI bleed
Nephritis
20-50%
Microscopic hematuria most common; ~5-15% progress to CKD
Clinical tetrad of IgA vasculitis (Henoch-Schönlein purpura).
Treatment
First-line
Supportive care — most pediatric cases resolve spontaneously within 4-6 weeks
Hydration, rest, acetaminophen, NSAIDs for arthralgia (avoid in severe renal disease)
Hospitalization for severe abdominal pain, GI bleeding, intussusception, or significant renal involvement
Corticosteroids (prednisone 1-2 mg/kg/day) for severe abdominal pain, GI bleeding, severe arthritis, scrotal pain, or CNS involvement — they do NOT prevent nephritis but shorten symptom duration
Skin and joint disease only
Symptomatic care
Compression stockings for recurrent purpura
Significant GI disease (severe pain, bleeding, intussusception risk)
Corticosteroids — prednisone 1-2 mg/kg/day for 1-2 weeks then taper
Surgical evaluation for intussusception (hydrostatic or surgical reduction)
IgA vasculitis nephritis (mild)
RAAS blockade — ACE inhibitor (lisinopril, enalapril) or ARB (losartan, valsartan) for proteinuria
Close monitoring of BP and urine
IgA vasculitis nephritis (moderate-severe — nephrotic, RPGN, crescents)
Corticosteroids — IV methylprednisolone pulse then oral prednisone
Add mycophenolate mofetil or cyclophosphamide for crescentic disease
Plasmapheresis in fulminant RPGN (limited evidence)
Rituximab in refractory adult cases
Second-line / adjunct
Azathioprine as steroid-sparing maintenance
Sparsentan (dual endothelin/ARB) — emerging role in IgA vasculitis nephritis based on IgA nephropathy data
Tonsillectomy — controversial; some evidence of benefit in refractory IgA nephritis (mostly Japanese data)
Kidney transplantation for ESKD — recurrence rate ~30%
Complications
Intussusception (most common abdominal complication in children) — typically ileoileal rather than ileocolic
GI bleeding, bowel perforation, bowel ischemia
Chronic kidney disease (5-15% of nephritis cases progress); higher in adults than children
IgA vasculitis is now the preferred term; Henoch-Schönlein purpura remains widely used clinically.
Steroids relieve abdominal and joint symptoms but do NOT prevent the development of nephritis — counsel families accordingly.
Intussusception in IgA vasculitis is typically ileoileal (small-bowel to small-bowel), so it may be missed by air-contrast enema (which mainly reduces ileocolic intussusception).
Adults with IgA vasculitis have higher rates of severe renal disease — always biopsy if significant proteinuria or rising creatinine.
Search for an underlying malignancy in adults presenting with IgA vasculitis, particularly age >50.
References
Chapel Hill 2012 — Jennette JC et al. 2012 Revised International Chapel Hill Consensus Conference Nomenclature of Vasculitides (Arthritis Rheum 2013;65:1-11)
EULAR/PRINTO/PReS — Ozen S et al. EULAR/PRINTO/PReS criteria for Henoch-Schönlein purpura, childhood polyarteritis nodosa, childhood Wegener granulomatosis and childhood Takayasu arteritis (Ann Rheum Dis 2010;69:798-806)
SHARE — Ozen S et al. European consensus-based recommendations for diagnosis and treatment of immunoglobulin A vasculitis (Rheumatology 2019;58:1607-1616)
KDIGO 2021 — KDIGO 2021 Clinical Practice Guideline for the Management of Glomerular Diseases (Kidney Int 2021;100:S1-S276)
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