Henoch Schönlein Purpura - IgA-Associated Vasculitis

Indications for Testing

Palpable purpura in children with other systemic symptoms

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)
- CBC – normal platelet count rules out idiopathic thrombocytopenic purpura
- Urinalysis – hematuria common
- ESR – may be elevated
- BUN/creatinine – may be elevated from renal involvement or dehydration
- Serum IgA – elevated in 50%

Histology

Granulocytes in arterioles and venule walls with IgA and C3 deposition

Imaging Studies

Ultrasound of gastrointestinal tract – for significant abdominal pain

Prognosis

Generally benign outcome; long-term prognosis depends on severity of renal involvement

Differential Diagnosis

Hematuria/glomerulonephritis
- Post streptococcal glomerulonephritis
- Systemic lupus erythematosus
- Idiopathic thrombocytopenic purpura (ITP)
- Hemolytic uremic syndrome
- Disseminated intravascular coagulation
- Wegener granulomatosis
Abdominal pain
- Intussusception
- Sepsis
- Pancreatitis
Arthralgias
- Endocarditis
- Sepsis
- Juvenile rheumatoid arthritis
Purpuric rash
- Meningitis
- Other vasculitides
- ITP
- Acute leukemias (ALL, AML)

Henoch Schönlein purpura (HSP) is a small-vessel vasculitis characterized by hematuria, purpura, arthritis and abdominal pain. 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 small vessel vasculitis characterized by tissue deposition of IgA containing immune complexes
Necrotizing small vessel vasculitis
Disease onset mostly occurs in the winter months, suggesting an infectious trigger
- Frequently (~50%) preceded by upper respiratory tract infection

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
Clinical tetrad of symptoms is classic
- Rash – palpable purpura (often concentrated on extensor surfaces of lower extremities)
- Polyarthralgia – most commonly in knees and ankles; often edema is also present
- Abdominal pain – nausea, emesis, diarrhea; colicky quality
- Renal disease – mild glomerulonephritis with microscopic hematuria, red cell casts, proteinuria
Other organ involvement
- Neurologic – rare; headache, encephalopathy, seizures
- Pulmonary – rare; diffuse alveolar hemorrhage

Treatment

Supportive – nonsteroidal anti-inflammatory drugs (NSAIDs)
Observe renal function to assure no renal failure

Tests generally appear in the order most useful for common clinical situations

Test name: CBC with Platelet Count & Automated Differential

ARUP #: 0040003

Methodology: Automated Cell Count with Flow Cell Differential

Use:

Differentiate between infectious and non-infectious process

Test name: Sedimentation Rate, Westergren (ESR)

ARUP #: 0040325

Methodology: Westergren

Use:

Assess for inflammation; typically elevated

Test name: Urinalysis, Complete

ARUP #: 0020350

Methodology: Reflective Photometry/Microscopic by Yellow IRIS

Use:

Screen for hematuria

Test name: Urea Nitrogen, Serum or Plasma

ARUP #: 0020023

Methodology: Quantitative Spectrophotometry

Use:

Screen for glomerulonephritis

Test name: Creatinine, Serum or Plasma

ARUP #: 0020025

Methodology: Quantitative Enzymatic

Use:

Screen for glomerulonephritis

Additional Tests Available

Test name: Immunoglobulin A

ARUP #: 0050340

Methodology: Quantitative Nephelometry

Comments:

Screen for elevation

General

Comprehensive Review: June 2011
Last Update: June 2011

Disseminated Intravascular Coagulation

Functional Platelet Disorders