Henoch-Schonlein Purpura (HSP)

Definition:

• It is a type of immune complex vasculitis with unknown cause characterized by

inflammation of the small vessels, lymphocytic infiltration of tissues, hemorrhage, and ischemia.

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Epidemiology:

• The most common systemic vasculitis of childhood.

• Usually affecting children between 3-15 years old.

• Slightly more common in males.

• Winter season predominance has been reported to be associated with HSP.

• 80% of the HSP was preceded by viral upper respiratory infection or streptococcal infection.

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Pathophysiology:

• Increased serum IgA concentration, IgA- containing immune complexes, and IgA deposition in walls of the vessels and renal mesangium.

• IgA1 abnormalities are more associated with HSP than IgA2.

• This deposition will evoke various inflammatory mediators including vascular prostaglandins, which may play a central role in the pathogenesis of HSP.

• Type III hypersensitivity reaction.

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Clinical presentation:

• Acute purpura in lower extremities and buttocks:

  • The hallmark of HSP is palpable purpura.

  • Start as maculopapular erythema to petechiae or purpura.

  • Usually appears below the waist covering the buttocks and lower limbs.

• Arthritis:

  •  Appears in 80% of HSP patients.

  •  Painful, in large joints of lower limb (hips, knees, and ankles joints) and disappear after few days.

  • ANCA negative

• Diffuse colicky abdominal pain:

  • Presents in the acute phase of HSP preceding the purpura.

  • Positive occult stool for blood and bloody diarrhea.

  • Intussusception (ileoileal/rare).

  • Pancreatitis, protein losing enteropathy/ hyrops of the gallbladder.

• Renal involvement

  •  Mostly mild with microscopic or macroscopic hematuria and low grade

    proteinuria.

  •  Hypertension and acute renal failure might occur.

  •  Acute IgA glomerulonephritis:

    • Focal segmental proliferative glomerulonephritis with mesangial hypercellularity.

• Might also present with orchitis, and subcutaneous edema.