- Small vessel vasculitis caused by immune complex (IC) deposition following an infectious trigger
- MC after infection caused by group A strep
- Primarily affects the skin and mucous membranes
- Leukocytoclastic vasculitis, increase incidence in winter
Epidemiology
- MC in children
- MC in boys
Pathophysiology
- Small-vessel vasculitis in which ICs of IgA and C3 are deposited on arterioles, venules and capillaries
- Type III HSR
- Involves skin, connective tissue, joints, scrotum, GIT and kidneys
- Association with vaccination for typhoid, cholera, measles, hep B
Clinical features
- Classic triad – purpura, arthritis and abdominal pain
- And GI hemorrhage
- Purpura is MC on legs and buttocks
- Abdominal pain – colicky
- Arthritis – MC on ankles, knees, elbows
- Kidney involved in 40% of cases
- Hematuria, proteinuria
Diagnosis
- Mainly based on combination of symptoms
- History of infection – group A β-hemolytic strep; HBV; HSV; Measles; H.pylori
- Blood (non-specific)
- ↑creatinine and urea – kidney involvement
- ↑CRP + ESR
- Immunofluorescence – demonstrates IgA + C3
Treatment
- Mostly self limiting
- Analgesia for abdominal and joint pain
- Corticosteroids – moderate to severe