IgA Vasculitis - Henoch Schönlein Purpura

Diagnosis

Indications for Testing

  • Palpable purpura in children with other systemic symptoms
  • Onset associated with an upper respiratory tract or gastrointestinal infection

Criteria for Diagnosis

  • Diagnosis is primarily clinical
  • American College of Rheumatology Criteria (1990)
    • 2 of 4 must be present – sensitivity 87.1%, specificity 82.7%
      • Palpable purpura
      • Age – <20 years
      • Bowel angina – defined as abdominal pain
      • Vascular wall granulocytes on biopsy seen in the arterioles and venules

Laboratory Testing

  • Nonspecific testing – helpful in excluding other diagnoses or identifying organ dysfunction
    • CBC – normal platelet count rules out idiopathic thrombocytopenic purpura
    • Urinalysis – hematuria common
    • Erythrocyte sedimentation rate (ESR) and C-reactive protein (CRP) – may be elevated
    • BUN/creatinine – may be elevated from renal involvement or dehydration
    • Serum IgA – elevated in 50% of patients

Histology

  • Granulocytes in small vessel (arterioles and venule walls) with IgA and C3 immune deposition
  • Glomerulonephritis may be indistinguishable from IgA nephropathy

Imaging Studies

  • Ultrasound of gastrointestinal tract – if significant abdominal pain present to rule out GI pathology

Prognosis

  • Generally benign outcome
  • Long-term prognosis depends on severity of renal involvement

Differential Diagnosis 

Clinical Background

Henoch Schönlein purpura (HSP) is classified as a small-vessel vasculitis that predominantly affects the skin, gastrointestinal tract and is largely associated with arthritis (Chapel Hill 2012). HSP is the most common vasculitis of childhood.

Epidemiology

  • Incidence – 13-14/100,000 in U.S.
  • Age – typically diagnosed in children age 3-10 years
    • 50% are diagnosed >5 years
  • Sex – M>F, 2:1

Pathophysiology

  • Systemic necrotizing small-vessel vasculitis characterized by tissue deposition of IgA containing immune complexes

Clinical Presentation

  • HSP is typically a benign, self-limited disorder
    • <5% of cases cause chronic symptoms
    • <1% of cases progress to end-stage renal failure
  • Classic clinical tetrad of symptoms
    • Rash – palpable purpura
      • Often concentrated on extensor surfaces of lower extremities
    • Polyarthralgia – most commonly in knees and ankles
      • Often edema also present
    • Abdominal pain – nausea, emesis, diarrhea; colicky quality
    • Renal disease – mild glomerulonephritis with microscopic hematuria, red cell casts, proteinuria
  • Other organ involvement
  • May present as single organ vasculitis
  • Disease onset mostly occurs in the winter months, suggesting an infectious trigger
    • Frequently preceded by upper respiratory tract infection – ~50% of cases
    • Also associated with gastrointestinal infection
  • May be associated with other diseases or these diseases may be causal
    • Liver disease
    • IBD
    • Ankylosing spondylitis

Indications for Laboratory Testing

  • Tests generally appear in the order most useful for common clinical situations
  • Click on number for test-specific information in the ARUP Laboratory Test Directory
Test Name and Number Recommended Use Limitations Follow Up
CBC with Platelet Count and Automated Differential 0040003
Method: Automated Cell Count/Differential

May help in ruling out infectious process

   
Sedimentation Rate, Westergren (ESR) 0040325
Method: Visual Identification

Initial evaluation for suspected vasculitis

   
C-Reactive Protein 0050180
Method: Quantitative Immunoturbidimetry

Initial evaluation for suspected vasculitis

   
Urinalysis, Complete 0020350
Method: Reflectance Spectrophotometry/Microscopy

Screen for hematuria, proteinuria, and RBC casts

   
Urea Nitrogen, Serum or Plasma 0020023
Method: Quantitative Spectrophotometry

Assess for renal involvement

   
Creatinine, Serum or Plasma 0020025
Method: Quantitative Enzymatic

Assess for renal involvement

   
Additional Tests Available
 
Click the plus sign to expand the table of additional tests.
Test Name and NumberComments
Immunoglobulin A 0050340
Method: Quantitative Nephelometry

Screen for elevation