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Snapshot
  • A 4-year-old boy presents to the emergency room with abdominal pain. His mother reports that he also had a rash for about a week on his lower extremities as well as joint pain and blood in his urine. Physical exam reveals palpable purpura on his buttocks and bilaterally on his legs and abdominal tenderness. On laboratory evaluation, there is no thrombocytopenia. The physician reassures his mother that this will resolve on its own and he will be monitored for renal involvement. 
Introduction
  • Clinical definition 
    • a systemic immune-mediated small vessel vasculitis often following an upper respiratory infection and characterized by IgA deposition and triad of 
      • palpable purpura
      • arthralgias
      • abdominal pain
  • Epidemiology
    • demographics
      • children < 10 years of age
      • most common childhood vasculitis
    • risk factors 
      • fall and winter months
      • family history
      • upper respiratory tract infection
        • especially with group A streptococcus or parvovirus B19
  • Etiology
    • associated with preceding upper respiratory infection
  • Pathogenesis
    • IgA immune complex deposition in the small vessels causes a vasculitis
      • deposition in the skin, gastrointestinal tract, and renal glomeruli cause physical manifestations of the disease
      • leukocytoclasis causes small vessel necrosis
  • Associated conditions
    • IgA nephropathy (Berger disease)
  • Prognosis
    • resolves spontaneously over time
    • typically lasts 4 weeks
Presentation
  • Symptoms
    • joint pains (arthralgias) of lower extremities
    • colicky abdominal pain
    • hematuria
    • constitutional symptoms
      • fever, malaise, or fatigue
  • Physical exam
    • symmetric palpable nontender purpura on buttocks and lower extremities
      • typically the first sign of the disease
      • may spread to upper extremities
    • abdominal tenderness on palpation
      • typically 1 week after onset of rash but can occur simultaneously
Studies
  • Labs
    • normal platelet count
      • presence of thrombocytopenia should prompt investigation into other causes of palpable purpura
    • normal coagulation profile
    • urine studies
      • proteinuria and hematuria indicates renal involvement
  • Biopsy
    • indications
      • most accurate test but usually not necessary
        • only indicated if the diagnosis is uncertain
    • findings
      • IgA deposition in small vessels seen on direct immunofluorescence
      • leukocytoclasis
  • Making the diagnosis
    • most cases are clinically diagnosed
Differential
  • Thrombotic thrombocytopenic purpura
    • distinguishing factors
      • FATRN
        • Fever
        • Anemia (microangiopathic hemolytic)
        • Thrombocytopenia
        • Renal failure
        • Neurological symptoms
      • schistocytes on peripheral blood smear
  • Polyarteritis nodosa
    • distinguishing factors
      • usually in adults
      • typically presents with ulcerative lesions but can also present with palpable purpura
      • associated with hepatitis B virus infection
      • "string of beads" (microaneurysms) on angiogram
Treatment
  • Management approach
    • as the disease resolves spontaneously over time, medical therapy is typically unnecessary, unless there is persistent nephropathy
  • Conservative
    • supportive care
      • indication
        • for all patients
      • modalities
        • hydration
        • pain management
  • Medical
    • angiotensin-converting enzyme (ACE) inhibitor
      • indication
        • for patients with persistent proteinuria
    • corticosteroids
      • indications
        • for patients with persistent proteinuria despite ACE-inhibitors
        • not recommended for prevention of renal disease
Complications
  • Persistent renal sequelae   
  • Recurrence
 

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