Henoch - Schonlein purpura
Also referred to as IgA vasculitis, Henoch-Schonlein purpura is a vasculitis that affects the small vessels, predominantly in children or young adults, with a propensity to affect males.
Henoch-Schonlein purpura predominantly affects capillaries, venules and arterioles, leading to skin, joint, GI and kidney involvement. Histopathologically, we can describe the vasculitis as a Leukkocytoclastic form, with some lymphocytes and variable eosinophils, along with IgA deposits in affected tissues.
Most commonly the condition is triggered by an upper respiratory tract infection, although medications can also trigger the condition, and it causes a classic tetrad of:
- Purpuric rash (usually over buttocks and extensor surfaces of upper and lower limbs - 100%)
- Abdominal pain (62%)
- Glomerulonephritis (with haematuria)(40%)
- Polyarthritis (80%)
Image: “Henoch-Schönlein nephritis IgA immunostaining” by Lazarus Karamadoukis, Linmarie Ludeman and Anthony J Williams, CC BY 2.0, via Wikimedia Commons.
Diagnosis is based on clinical suspicion along with increased creatinine and urea, raised CRP and ESR and a normal or raised platelet count which distinguishes it from other causes of purpura such as AI thrombocytopenia, SLE or leukemia. If still in doubt a biopsy can be taken of the skin lesion. Where two of the following four can be confirmed, HSP can be diagnosed:
- Palpable purpura
- Bowel angina
- Diagnostic biopsy showing granulocytes in walls with IgA deposits
- <20 y.o.
Onset is generally acute, along with a fever. Typically the disease is self limiting, lasting on average 4 weeks, however glucocorticoids (40-60mg/day) may be required.