A 3-year-old

boy was brought to the paediatrician after his parents had noticed

reddish-purple spots (rash) on the buttocks, legs and feet. Moreover, they also

reported abdominal pain with nausea and vomiting. Further examinations

performed by the doctor led to a diagnosis of glomerulonephritis. A skin biopsy

of the lesions revealed leukocytoclastic vasculitis and venular thrombosis

whereas IgA immune complex deposition was identified within the wall and lumen

of the dermal vessels.

Which

vasculitis is most likely responsible for the above clinicopathological findings?