Harvey's Garden

IgA vasculitis

Properties2
tagst1
aliasesHenoch-Schonlein purpura, HSP, Henoch-Schönlein purpura

3 min read

Epidemiology

  • Sex: ♂ > ♀
  • Age: more common in children
    • 90% of affected individuals < 10 years
    • Other small vessel vasculitides mainly affect adults

Etiology

  • Preceding infection
    • Up to 90% of cases are preceded by viral or bacterial infection 1–3 weeks prior.
    • Most commonly an upper respiratory tract infection caused by group A Streptococcus
    • IgA nephropathy
    • Drugs

Pathophysiology

Hypothesized pathophysiological mechanism: exposure to allergen/antigen (e.g., infection, drugs) → stimulation of IgA production → deposition of IgA immune complexes in vascular walls (e.g., in the skin, GI tract, joints, kidneys) → activation of complement → vascular inflammation and damage

Clinical features

Key features

  • Triad of palpable purpura, arthralgias, and abdominal pain in children.
  • Afebrile, which differentiates its with infectious disease

  • The classic tetrad includes: c
    1. Palpable Purpura: Present in nearly all patients, typically non-pruritic and symmetrically distributed on the lower extremities and buttocks. The rash begins as erythematous or urticarial lesions that evolve into palpable purpura. c
    2. Arthritis/Arthralgia: Occurs in ~75% of patients, presenting as transient, non-destructive joint pain and swelling, most commonly affecting the ankles and knees.
    3. Abdominal Pain: Affects 50-75% of patients; it is often colicky. Can be associated with nausea, vomiting, and GI bleeding (melena or hematemesis).
    4. Renal Disease: Occurs in 40-50% of patients and is the main determinant of long-term prognosis. It can range from microscopic hematuria and mild proteinuria to a rapidly progressive glomerulonephritis.
  • Scrotal edema can also be seen, particularly in young boys. c

Tip

  • IgA Nephropathy and IgA Vasculitis (Henoch-Schönlein Purpura) are considered different clinical presentations of the same biological process.
  • IgA Nephropathy = Renal-limited form.
  • IgA Vasculitis = Systemic form involving skin, joints, GI tract, and kidneys.

Tip

IgAV is an important differential diagnosis to consider in children with a limp.

Diagnostics

Biopsy

  • IgA and C3 complex deposition (hallmark) in small vessels of the superficial dermis
  • ANCA negative vasculitis

Differential Diagnosis

See Purpura differential diagnosis

  • Immune Thrombocytopenic Purpura (ITP): Diff by isolated severe thrombocytopenia, non-palpable petechiae/purpura, absence of systemic symptoms (no GI/joint/renal involvement).
  • Hemolytic Uremic Syndrome (HUS): Diff by triad of microangiopathic hemolytic anemia (schistocytes on peripheral smear), thrombocytopenia, and acute renal failure following diarrheal prodrome (E. coli O157:H7).
  • Poststreptococcal Glomerulonephritis (PSGN): Diff by low serum C3, longer latency after infection (1–6 wks), and lack of purpura or arthritis.
  • Meningococcemia: Diff by toxic appearance, high fever, hypotension, and purpura fulminans.
  • Hypersensitivity Vasculitis: Diff by exposure to offending drug; lacks prominent GI or renal manifestations.

Treatment

Complications

  • Intussusception: Most common GI complication; classically ileoileal (lead point caused by focal submucosal bowel wall hematoma), unlike typical idiopathic ileocolic intussusception. c
  • Gastrointestinal: Bowel ischemia, perforation, stricture formation.
  • Renal: End-stage renal disease (ESRD) or chronic kidney disease (CKD) (<5% of pediatric cases; higher risk in adults).

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